Geometric Ratio Research Articles

Study on the thermal control performance of lightweight minimal surface lattice structures for aerospace applications

With the rapid evolution of aerospace technology and the increasing complexity of space environments, the demand for lightweight, thermally insulated, and highly efficient heat dissipation materials in aircraft equipment has surged. This study addresses this critical need by investigating Triply Periodic Minimal Surface (TPMS) lattice structures, offering a novel design approach to enhance spacecraft thermal management under extreme temperatures. Our work introduces a methodology to quantitatively assess the thermal insulation and heat dissipation performance of various lightweight lattice sandwich structures. We constructed implicit function models of low volume fractions, including Gyroid, Diamond, Primitive, and IWP, and conducted experiments using an active cooling setup under controlled heating conditions at 300 °C. Key findings reveal that, at flow velocities ranging from 0.25 to 1.5 m/s, the Diamond model exhibited the highest convective heat transfer coefficient, surpassing the Gyroid, Primitive, and IWP models by 6.9 % to 427.3 %, 87.1 % to 485.6 %, and 1.5 % to 98.7 %, respectively. Conversely, at velocities between 1.5 and 3.75 m/s, the Gyroid model demonstrated superior heat exchange performance, improving by 14.6 % to 67.2 %, 73 % to 167.7 %, and 9 % to 64.8 % compared to the Diamond, Primitive, and IWP models. During thermal insulation tests at temperatures from 200 to 400 °C, the Diamond model showed the best insulation effect, while the Primitive model performed poorly. Based on the experimental data, we established empirical relationships between the Nusselt number, friction coefficient, and Geometric Surface Ratio (GS). These findings not only underscore the significant potential of TPMS lattice structures in aerospace applications but also provide a robust theoretical framework and practical guidelines for achieving efficient thermal management in lightweight aerospace manufacturing.

P-97. Safety, Tolerability, and Immunogenicity of Revaccination With mRNA-1345, an Investigational Vaccine Against RSV, Given at 12 Months Following a Primary Dose in Adults Aged ≥ 50 Years

Abstract Background mRNA-1345 is an investigational RSV vaccine that has demonstrated efficacy for the prevention of lower-respiratory tract disease in older adults. The duration of protection and need for revaccination have not yet been defined. Interim findings are presented from a phase 3 trial evaluating mRNA-1345 revaccination at 12 months after a primary dose in adults aged ≥ 50 years. Figure 1. Methods Part C of a multi-part, ongoing, phase 3 trial (NCT05330975) evaluated the safety, tolerability, and immunogenicity of open-label revaccination with mRNA-1345 (50 µg) in participants aged ≥ 50 years who previously received a primary dose of mRNA-1345 in Part B of the trial. Safety, tolerability, and immunogenicity (RSV-A and RSV-B neutralizing antibody [nAb] responses) of revaccination were primary objectives. Non-inferiority of immune responses was assessed via geometric mean titer ratio (GMR; 95% CI lower bound > 0.667) at Day 29 post-revaccination (Part C) versus Day 29 post-primary dose (Part B). Results of the Day 29 post-revaccination interim analysis are presented here. Results Overall, 543 participants were revaccinated with mRNA-1345 (50 µg). Solicited local and systemic adverse reactions within 7 days post revaccination were reported by 55.8% and 50.3% of participants, respectively. Injection site pain (54.3%), headache (33.5%), myalgia (33.5%), fatigue (31.1%), and arthralgia (28.5%) were most frequently reported (≥ 20%) and were primarily grade 1 or 2 in severity. Up to 28 days after revaccination, no adverse events (AEs) led to study discontinuation, and no fatalities or vaccine-related serious AEs, AEs of special interest, or severe AEs were reported. All coprimary immunogenicity endpoints met pre-specified criteria for non-inferiority based on Day 29 GMRs (revaccination Day 29 vs primary Day 29); nAb GMRs (95% CI) were 1.08 (0.99, 1.17) for RSV-A and 0.91 (0.84, 0.99) for RSV-B (Figure 1). Conclusion Revaccination with mRNA-1345 administered 12 months after a primary dose was well-tolerated, had no identified safety concerns, and elicited RSV nAbs at Day 29 that were non-inferior to those after a primary mRNA-1345 dose in adults aged ≥ 50 years. These data support mRNA-1345 revaccination at 12 months after primary vaccination if the need for revaccination is determined. Disclosures Jaya Goswami, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Denise C. Hsu, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Alana Simorellis, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Lauren Wilson, MSN, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Rakesh Dhar, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Xiaowei Wang, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Archana Kapoor, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Avi Collins, BScN, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Vinicius Righi, PharmD, MBA, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Lan Lan, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Jiejun Du, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Honghong Zhou, Ph.D., Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Sonia K. Stoszek, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Christine A. Shaw, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Caroline Reuter, MD, MSCI, Moderna, inc.: Employee|Moderna, inc.: Stocks/Bonds (Public Company) Eleanor Wilson, MD, MHS, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Jacqueline Miller, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company) Rituparna Das, M.D., Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds (Public Company)

Magnon signatures of multidimensional reconfigurations in multilayer square artificial spin ices

We present an all-electrical, broadband spin-wave spectroscopy study of three-dimensional square artificial spin ices composed of dipolarly coupled ferromagnetic layers of varying thicknesses separated by a non-magnetic spacer. Our experiments, in the saturated regime, reveal that the spin-wave spectra exhibit a strong dependence on both the angle of the applied magnetic field and the geometrical aspect ratio of the ferromagnetic layers. Micromagnetic simulations and analytical calculations, utilizing the Smit–Beljers formalism, demonstrate good agreement with our experimental findings. In the magnetic switching regime, the spin-wave spectra indicate an antiparallel alignment between the two ferromagnetic layers. This configuration is highly sensitive to the field angle, suggesting the presence of multidimensional reconfigurations within the multilayer artificial spin ice. Furthermore, employing a minor loop field protocol, we show that the spin-wave modes associated with the antiparallel alignment remain reproducible, even after 100 minor loop cycles, providing intriguing possibilities for magnonic engineering.

Post hoc analysis: 6 Months immunogenicity after third dose of BNT162b2 vs JNJ-78436735 After Two Doses of BNT162b2 vaccine in Solid Organ Transplant Recipients.

In Solid Organ Transplant (SOT) recipients, due to immunosuppression, the immunogenicity after COVID-19 vaccination is suboptimal and its durability is unknown. We conducted a post-hoc analysis of a patient-blinded, single center, randomized controlled trial comparing BNT162b2 vs JNJ-78436735 as the third dose after two doses of BNT162b2 in adult SOT recipients with active graft to compare long-term immunogenicity. Forty-one recipients were analyzed. Median IgG levels against SARS-CoV-2 at 6 months were 53,747 (range 949 - 657,558) and 7,632 (range 642 - 672,000) AU/ml for BNT162b2 vs JNJ-78436735, respectively (p=0.017). The median geometric mean fold increase ratio at 6 months was 37.2 (0.12-618.5) and 4.30 (0.1-204.2) for BNT162b2 vs JNJ-78436735, respectively (p<0.05). After two doses of BNT162b2, homologous approach with BNT162b2 achieved a superior immunogenicity compared to heterologous approach with JNJ-78436735. In this post hoc analysis, we report durability of specific IgG between two vaccine strategies and found no statistically significant difference between two groups. (Clinical Trial Registry: NCT05047640).

Immunogenicity, safety, and reactogenicity of concomitant administration of the novavax vaccine against Omicron XBB.1.5 (NVX-CoV2601) and a 20-valent pneumococcal conjugate vaccine in adults aged ≥60 years: A randomised, double-blind, placebo-controlled, non-inferiority trial.

There is conflicting evidence as to whether the combined administration of two vaccines can lead to poorer immunogenicity and reactogenicity. The co-administration of the Omicron-adapted COVID-19 vaccine from Novavax (NVX-CoV2601) and a 20-valent pneumococcal conjugate vaccine (PCV20) has not been previously investigated. In this randomised, double-blind, placebo-controlled, non-inferiority trial, immunocompetent participants aged ≥60 years were randomised in a 1:1:1:1 ratio to four groups: NVX-CoV2601 plus PCV20 (combination group); NVX-CoV2601 plus placebo (NVX-only group); PCV20 plus placebo (PCV20-only group); or placebo plus placebo (placebo group). The primary outcome was Omicron-specific anti-spike protein IgG ELISA units at day 28 in the combination group compared with the NVX-only group. Non-inferiority was established if the lower limit of the two-sided 95% CI of the geometric mean titre ratio was above the non-inferiority margin of 0.67. Secondary outcomes included anti-pneumococcal capsular polysaccharide (PCP) IgG ELISA units. Solicited local and systemic adverse events were collected for 7 days after vaccination. This study was registered with ClinicalTrials.gov, number NCT05767606, and the EU Clinical Trials Register, EudraCT number 2022-004118-12. All 256 randomised participants completed the study. The baseline characteristics were similar in the four groups. Overall, the median age was 64 (IQR 61 to 69) and 105 (41%) of 256 were male. At day 28, the geometric mean anti-spike protein IgG ELISA units were 534U/mL (95% CI 432-660) in the combination group and 556U/mL (95% CI 460-672) in the NVX-only group, resulting in a geometric mean titre ratio of 0.96 (95% CI 0.73-1.27), thereby meeting the criteria for non-inferiority. Anti-PCP IgG ELISA units at day 28 were 507U/mL (95% CI 416-619) in the combination group and 592U/mL (95% CI 485-723) in the PCV20-only group. Local and systemic reactogenicity was similar in the three active treatment groups. No safety concerns or serious adverse events were observed. Immunogenicity following co-administration of NVX-CoV2601 with PCV20 was non-inferior to administration of NVX-CoV2601 alone. Given the similar safety and reactogenicity profile, our findings may help to overcome concerns about concomitant vaccination and pave the way for combination vaccines. Novavax.

Numerical Study of Carreau Fluid Flow in Symmetrically Branched Tubes

The non-Newtonian Carreau fluid model is a suitable model for pseudoplastic fluids and can be used to characterize fluids not so different from biological fluids, such as the blood, and fluids involved in geological processes, such as lava and magma. These fluids are frequently conveyed by complex flow structures, which consist of a network of channels that allow the fluid to flow from one place (source or sink) to a variety of locations or vice versa. These flow networks are not randomly arranged but show self-similarity at different spatial scales. Our work focuses on the design of self-similar branched flow networks that look the same on any scale. The flow is incompressible and stationary with a viscosity following the Carreau model, which is important for the study of complex flow systems. The flow division ratios, the flow resistances at different scales, and the geometric size ratios for maximum flow access are studied, based on Computational Fluid Dynamics (CFD). A special emphasis is placed on investigating the possible incidence of flow asymmetry in these symmetric networks. Our results show that asymmetries may occur for both Newtonian and non-Newtonian fluids and shear-thinning fluids most affect performance results. The lowest flow resistance occurs when the diameters of the parent and daughter ducts are equal, and the more uniform distribution of flow resistance occurs for a ratio between the diameters of the parent and daughter ducts equal to 0.75. Resistances for non-Newtonian fluids are 4.8 to 5.6 times greater than for Newtonian fluids at Reynolds numbers of 100 and 250, respectively. For the design of engineering systems and the assessment of biological systems, it is recommended that the findings presented are taken into account.

Constructing slope conceptualizations: Physical, geometrical, and algebraic

The concept of slope constitutes a fundamental component of the discourse surrounding linear equations. A subset of students frequently interprets slope merely as an algebraic ratio. This particular context fosters a superficial understanding of slope, as these students typically resort to mechanical memorization of the slope formula. The intent of this research endeavor is to enhance a holistic understanding of the slope concept: physically, geometrically, algebraically; through the deployment of realistic teaching activities. Two students are participants in this research endeavor. The research group initiated a series of questions aimed at assessing their comprehension by delivering a total of six activities, which were systematically designed using the emergent modeling framework central to the educational design principles of Realistic Mathematics Education (RME). These activities are structured to facilitate the students' understanding of the fundamental concept of slope, transitioning from physical properties, through geometric ratios, to algebraic ratios. Subsequent to the investigations and the interviews conducted, the researchers deduce that the utilization of realistic activities significantly enhances students' comprehension of the foundational concept of slope: physical, geometric, algebraic.

Vibration response of small-scaled FG-CNTRC sandwich plates with MR fluid core supported by Kerr elastic substance

The current work is a continuation of the previous work by proposing the refined zigzag theory (RZT) for the vibration response of the micro sandwich plate. The face sheets of this structure are magnetostrictive and reinforced with single-walled carbon nanotubes (SWCNT) in four different patterns (FG-AV, FG-O, FG-X, and UD) following the rule of mixtures (ROM). The core material contains magnetorheological (MR) fluid which can work as a damper under a magnetic field. The micro sandwich plate is supported by an elastic substance utilizing the Kerr model. Additionally, the modified couple stress theory (MCST) is employed to predict size effects, and the magnetostrictive material (MsM) properties are considered viscoelastic based on the Kelvin–Voigt model. The Hamilton principle is applied to derive the size-dependent equations of motion. Then, an analytical solution is presented to evaluate the efficacies of various parameters including the volume fractions and the functional arrangement of carbon nanotubes, the geometrical aspect ratio of the system, the magnetic field intensity, the type of MR fluid, the small-scale parameter, damping coefficients of the system, and the elastic medium. Consequently, 29% increase in the dimensionless frequency for [Formula: see text] is indicated when the small scale changes from [Formula: see text] to [Formula: see text]. This research can be contributed to the design and optimization of systems that use micro sandwich plates, addressing practical and essential engineering considerations.

Numerical study of the influence of the geometrical aspect ratio and nanoparticles diameter on forced convection in a micro-channel heat sink of a nanofluid water/CuO based on a Brownian diffusion model

In order to cool electronic equipment with a high efficiency we can use the flow of a nanofluid in a rectangular micro-channel heat sink. The paper reports the results of the study of a hydrodynamically fully developed laminar forced convective heat transfer flow in two different geometries G1and G2. The study is numerical and was achieved using as nanofluid with and a single-phase approach. Calculations were first made with constant thermo-physical properties at and then made using temperature and nanoparticles diameter dependent thermo-physical properties based on a Brownian diffusion model. A three-dimensional conjugate heat transfer model was used and numerical simulations were based on a finite volume method. The simulations were made for a range of Reynolds numbers , for nanoparticle diameter in the range of and for a heat flux through the bottom surface of the heat sinks .The results of thermal and hydrodynamic fields show that nanofluids can provoke an increase in the local and average Nusselt numbers, a decrease of bottom surface local temperature and a slight decrease of the shear stress on the wall, particularly in the case of geometry G2. At the end of the study, the best geometry, volume fraction of nanofluid and nanoparticle diameter to be recommended for cooling were found based on minimum total thermal resistance of the micro-channel heat sink.

Angstrom Scale Ionic Memristors' Engineering with van der Waals Materials: A Route to Highly Tunable Memory States.

Memristors that mimic brain functions are crucial for energy-efficient neuromorphic devices. Ion channels that emulate biological synapses are still in the early stages of development, especially the tunability of memory states. Here, we demonstrate that cations such as K+, Na+, Ca2+, and Al3+ intercalated in the interlayer spaces of vermiculite result in highly confined channels of size 3-5 Å. They host exotic memristor properties through ion exchange dynamics, even at high salt concentrations of 1 M. The bipolar memristor characteristics observed are tunable with frequency, geometric asymmetry, ion concentration, and intercalants. Notably, we observe polarization-flipping memristor behavior in two cases: one with Al3+ ions and another with devices having a geometric asymmetry ratio greater than 15. This inversion is attributed to the overscreening of counterions due to their accumulation at the channel entrance. Our results suggest that ion exchange dynamics, ion-ion interactions, and ion accumulation/depletion mechanisms, particularly with multivalent ions, can be harnessed to develop advanced memristor devices.

Study of the failure characteristics and mechanical response of railway tunnel under oblique-slip fault displacement

When a tunnel intersects an active fault, the dislocation of the fault often leads to failures such as lining fractures and structural deformations, severely threatening the safe operation of the tunnel. To investigate the fracture characteristics and mechanical responses of tunnels under oblique-slip fault conditions, a large-scale indoor model test with a geometric similarity ratio of 1:35 was conducted. This study was based on a railway tunnel in Western China that crosses an oblique-slip active fault. Additionally, a three-dimensional model of the tunnel-surrounding rock-fault fracture zone interaction was established using ABAQUS finite element analysis software. The purpose of this study is to clarify the structural cracking characteristics, deformation modes, strain trends, changes in bending moment and shear force of tunnels under fault displacement, as well as the contact force between tunnels and surrounding rocks, and further reveal the differences in the impact of oblique-slip faults and other types of faults on tunnels. The results indicate that under oblique-slip fault dislocation, the tunnel experiences shear failure at the fault fracture zone manifested as shear diagonal cracks. Tensile bending failures, characterized by bending circumferential cracks, occur at the hanging wall and footwall. At the fault fracture zone, the strain, contact pressure, bending moment, and shear force of the tunnel undergo drastic changes and peak values appear. The tunnel exhibits distinct three-dimensional failure characteristics, including horizontal bending, axial stretching and twisting, and vertical shearing. The damage zone of the tunnel extends approximately 2D (where D is the tunnel diameter) from both the hanging wall and footwall towards the fault fracture zone, with the severity of damage increasing closer to the fault fracture zone. The damage process of the tunnel under increasing fault dislocation displacement can be divided into three stages: initial intact stage, onset of damage stage, and complete failure stage. When the strike-slip dislocation reaches 20.7 mm (corresponding to an actual displacement of 724.5 mm), structural damage accumulates to its limit, leading to large-scale failure of the tunnel. Compared to purely strike-slip faults, the tunnel is more prone to damage and exhibits a larger range of structural failure under oblique-slip fault dislocation. These findings provide scientific and rational data support and reference for disaster prevention and mitigation design of tunnels.

Safety and immunogenicity of an inactivated recombinant Newcastle disease virus vaccine expressing SARS-CoV-2 spike: A randomised, comparator-controlled, phase 2 trial

Production of affordable coronavirus disease 2019 (COVID-19) vaccines in low- and lower-middle-income countries is needed. NDV-HXP-S is an inactivated egg-based recombinant Newcastle disease virus vaccine expressing the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A public sector manufacturer in Vietnam assessed the immunogenicity of NDV-HXP-S (COVIVAC) relative to an authorized vaccine. This phase 2 stage of a randomised, observer-blind, controlled, phase 1/2 trial was conducted at three community health centers in Thai Binh Province, Vietnam. Healthy males and non-pregnant females, 18years of age and older, were eligible. Participants were randomised by age (18-59, ≥60years) to receive one of three treatments by intramuscular injection twice, 28days apart: COVIVAC at 3μg or 6μg, or AstraZeneca COVID-19 vaccine VAXZEVRIA™. Participants and personnel assessing outcomes were masked to treatment. The vaccine dose was selected based on Phase 1 results. A 6μg dose was chosen to explore the immunogenicity gain over the 3-μg dose. The study's aim is to evaluate the safety and immunogenicity of COVIVAC at two dose levels compared to VAXZEVRIA, the most commonly used COVID-19 vaccine in Vietnam. The main outcome was the induction of 50% neutralising antibody titers against vaccine-homologous pseudotyped virus 14days (day 43) and 6months (day 197) after the second vaccination by age group. The primary immunogenicity and safety analyses included all participants who received one dose of the vaccine. ClinicalTrials.govNCT05940194. During August 10-23, 2021, 737 individuals were screened, and 374 were randomised (124-125 per group); all subjects received vaccine dose one and all but three received doses two four weeks later. Subjects 18-59years of age achieved the following geometric mean titers of PNA 14days after vaccine dose two: 153⋅28 (95 % CI 124·2-189⋅15) for COVIVAC 3μg, 176⋅2 (95 % CI 141⋅45-220.27) for COVIVAC 6μg, and 99⋅92(95 % CI 80.80-123⋅56) for VAXZEVRIA. Subjects ≥60years of age also achieved potent geometric mean titers of PNA at the same timepoint: 183⋅57 (95 % CI 133.4-252⋅61) for COVIVAC 3μg, 257⋅87 (95 % CI 181⋅6-367⋅18) for COVIVAC 6μg, and 79⋅49(95 % CI 55⋅68-113⋅4) for VAXZEVRIA. On day 43, the geometric mean fold rise of 50% neutralising antibody titers for subjects age 18-59years was 31·20 (COVIVAC 3μgN=82, 95 % CI 25·14-38·74), 35·80 (COVIVAC 6μg; N=83, 95 % CI 29·03-44·15), 18·85 (VAXZEVRIA; N=82, 95 % CI 15·10-23·54), and for subjects age≥60years was 37·27 (COVIVAC 3μg; N=42, 95% CI 27·43-50·63), 50·10 (COVIVAC 6μg; N=40, 95% CI 35·46-70·76), 16·11 (VAXZEVRIA; N=40, 95 % CI 11·73-22·13). Among subjects seronegative for anti-S IgG at baseline, the day 43 geometric mean titer ratio of neutralising antibody (COVIVC 6μg/VAXZEVRIA) was 1·77 (95 % CI 1·30-2·40) for subjects age 18-59years and 3·24 (95% CI 1·98-5·32) for subjects age≥60years. On day 197, the age-specific ratios were 1·11 (95% CI 0·51-2·43) and 2·32 (0·69-7·85). Vaccines were well tolerated; reactogenicity was predominantly mild and transient. The percentage of subjects with unsolicited adverse events (AEs) during 28days after vaccinations was similar among treatments (COVIVAC 3μg 29·0%, COVIVAC 6μg 23·2%, VAXZEVRIA 31·2%); no vaccine-related AE was reported. Considering that induction of neutralising antibodies against SARS-CoV-2 has been correlated with the efficacy of COVID-19 vaccines, including VAXZEVRIA, our results suggest that vaccination with COVIVAC may afford clinical benefit matching or exceeding that of the VAXZEVRIA vaccine. ClinicalTrials.govNCT05940194.

Mesh Sensitivity Analysis of Axisymmetric Models for Smooth–Turbulent Transient Flows

The current paper focuses on the assessment of radial mesh influence on the description of the transient event obtained by an axisymmetric model. The objective is to reduce computational effort while accurately calculating hydraulic transients in smooth–turbulent pressurized pipes. The analyzed pipe system has a reservoir–pipe–valve configuration with an inner diameter of 0.02 m and a total length of 14.96 m, with the initial discharge being equal to 120 × 10−3 L/s (Re = 7638). An extensive study is carried out with 80 geometric sequence meshes by varying the total number of cylinders, the geometric common ratio, and the pipe axial discretization. The benefit of increasing the geometric common ratio is highlighted. A detailed comparison between two meshes is presented, in which the best mesh (i.e., the one with the lowest computational effort) has a three-fold higher value of the geometric common ratio. The two meshes show small differences for the instantaneous valve closure, limited to a time interval immediately after the arrival of the pressure surge and only during the first pressure wave. The dynamic characterization of the transient phenomenon demonstrates the in-depth consistency between the model results and the hydraulic transients’ phenomenon in terms of the piezometric head, the wall shear stress, and the mean velocity time-history, in comparison to the results obtained with the shear stress, lateral velocity, and axial velocity profiles.

Physical Model Experiments and Numerical Simulation Study on the Formation Mechanisms of Landslides on Gently Inclined Loess–Bedrock Contact Surfaces—A Case Study of the Libi Landslide in Shanxi Province

Landslides on gently inclined loess–bedrock contact surfaces are common geological hazards in the northwestern Loess Plateau region of China and pose a serious threat to the lives and property of local residents as well as sustainable regional development. Taking the Libi landslide in Shanxi Province as a case study (with dimensions of 400 m × 340 m, maximum thickness of 35.0 m, and volume of approximately 3.79 × 104 m3, where the slip zone is located within the highly weathered sandy mudstone layer of the Upper Shihezi Formation of the Permian System), this study employed a combination of physical model experiments and numerical simulations to thoroughly investigate the formation mechanism of gently inclined loess landslides. Via the use of physical model experiments, a landslide model was constructed at a 1:120 geometric similarity ratio in addition to three scenarios: rainfall only, rainfall + rapid groundwater level rise, and rainfall + slow groundwater level rise. The dynamic changes in the water content, pore water pressure, and soil pressure within the slope were systematically monitored. Numerical simulations were conducted via GEO-STUDIO 2012 software to further verify and supplement the physical model experimental results. The research findings revealed that (1) under rainfall conditions alone, the landslide primarily exhibited surface saturation and localized instability, with a maximum displacement of only 0.028 m, which did not lead to overall instability; (2) under the combined effects of rainfall and rapid groundwater level rise, a “sudden translational failure mode” developed, characterized by rapid slope saturation, abrupt stress adjustment, and sudden overall instability; and (3) under conditions of rainfall and a gradual groundwater level rise, a “progressive translational failure mode” emerged, experiencing four stages: initiation, development, acceleration, and activation, ultimately resulting in translational sliding of the entire mass. Through a comparative analysis of physical model experiments, numerical simulation results, and field monitoring data, it was verified that the Libi landslide belongs to the “progressive translational failure mode”, providing important theoretical basis for the identification, early warning, and prevention of such types of landslides.

Effects of increased rainfall on heat and mass transfer and deformation of sulfate saline soil: An experimental investigation

To study the effect of increased rainfall on the heat and mass transfer and deformation characteristics of sulfate saline soil, a geometric similarity ratio model (1:6) of the natural site was created inside the self-developed indoor baseplate-atmospheric dual-temperature control model box. For the first time, combined with the characteristics of the surface energy change, the characteristics of water-heat-salt-mechanical coupling changes within sulfate saline soil under normal rainfall and twice the increase in rainfall were studied. The results show that the increased rainfall leads to a more significant decrease in upward shortwave radiation and downward longwave radiation, as well as a more significant increase in the surface net radiation and surface evaporation rate. Additionally, the increase in rainfall leads to an obvious cooling trend in the surface temperature. Compared with normal rainfall, an increase in rainfall leads to a significant increase in soil water content and conductivity, while soil heat flux and temperature significantly decrease. The increased rainfall caused a temperature drop of 1.6 °C at 5 cm of saline soil. Moreover, the increased rainfall leads to an increase in the heat release time of sulfate saline soil. Meanwhile, the impact of increased rainfall on the soil water content, conductivity, and temperature gradually weakens with increasing depth. The increased rainfall can exacerbate thawing settlement deformation and alleviate salt frost heave deformation. Compared with normal rainfall, twice the increase in rainfall results in a 0.9 mm increase in thawing settlement deformation and a 2.5 mm decrease in salt frost heave deformation.

Research on the Criteria for Determining the Starting Performance of an Inward-Turning Inlet by Integrating the Concept of the Equivalent Contraction Ratio

The prediction of hypersonic inlet starting performance is crucial for the successful ignition of the combustion chamber, directly impacting the overall performance of the propulsion system. This challenge arises especially when freestream conditions vary. Therefore, this paper proposes the concept of the equivalent contraction ratio, and establishes and analyzes the intrinsic correlation between the geometric contraction ratio and angle of attack on the starting performance of three-dimensional inward-turning inlet. The results indicate the following: (1) The startability index can be applied to determine the start boundary of the three-dimensional inward-turning inlet under conditions of the freestream Mach number of 6.0 and an altitude of 27 km, with a deviation of no more than 6.6% from the optimal SI = 0.087 criterion; (2) The start boundary after applying the equivalent contraction ratio shows deviations not exceeding 4.0% under positive angle-of-attack conditions compared to the startability index, while the deviation is larger under negative angle-of-attack conditions, reaching a maximum of 13.3%. After applying a correction formula, the deviations can be reduced to within 2.0%; (3) For the same equivalent contraction ratio, the differences in starting performance between different positive and negative angle-of-attack conditions may fundamentally arise from the degree of compression of the inlet. Finally, the equivalent contraction ratio theory is proven to be able to quickly and easily predict the accurate starting performance of the inward-turning inlet at different angles of attack, improving the breadth and efficiency of engineering predictions.

Experimental Study on Identification of Aerodynamic Damping Matrix for the Tower of an Operating Wind Turbine by Artificial Excitation

ABSTRACTQuantitation of damping is of great significance for the design and condition assessment of wind turbines. The authors' previous theoretical and numerical studies showed that compared with damping ratios, a modal aerodynamic damping matrix can better describe the damping coupling in the fore‐aft (FA) and side‐side (SS) tower motions. In the present study, an improved damping identification method was first proposed to identify this damping matrix with artificial exciters and then verified by using OpenFAST simulations under different excitation frequencies, excitation force amplitudes, and turbulent wind fields. Following the numerical study, a scaled wind turbine model with a geometric scale ratio of 1/75 was carefully designed based on the NREL 5‐MW wind turbine prototype, in which the scaled blade design follows the rule in thrust coefficient similarity. An identification study was performed with this scaled model by a series of wind tunnel tests. The modal aerodynamic damping matrix was identified under steady‐state harmonic excitation in the operating state and compared with the identified results by a free decay method and the theoretical values. The results experimentally confirm the correctness of the aerodynamic damping matrix theory under uniform wind and the feasibility of the improved identification method in practice.

HPV16/18 antibodies 16-years after single dose of bivalent HPV vaccination: Costa Rica HPV vaccine trial.

The Costa Rica HPV Vaccine Trial provided initial evidence that 1 dose of the bivalent human papillomavirus (HPV) vaccine induces stabilizing antibody levels that may provide extended protection against HPV-16/18 infections. We report antibody seropositivity and stability 11 to 16 years after vaccination. We invited a random subset of Costa Rica HPV Vaccine Trial participants (n = 398) who had received 3 doses and all women (n = 203) who had received 1 dose at 18 to 25 years of age to follow-up visits 11, 14, and 16 years after vaccination. We calculated HPV-16 and HPV-18 seropositivity and assessed change in enzyme-linked immunosorbent assay antibody levels 11 to 16 years after vaccination among 500 participants. By year 16, 99.4% (95% confidence interval [CI] = 96.8% to 100.0%) and 100.0% (95% CI = 98.9% to 100.0%) of 1-dose and 3-dose recipients, respectively, were HPV-16 seropositive and 98.8% (95% CI = 95.9% to 99.9%) and 100% (95% CI = 98.9% to 100.0%) of 1-dose and 3-dose recipients, respectively, were HPV-18 seropositive. Between years 11 and 16, women who had received 3 doses had a small but statistically significant decrease in the geometric mean concentration for HPV-16 of ‒12.4% (95% CI = ‒16.3% to ‒8.4%) and HPV-18 of ‒13.4% (95% CI = ‒17.2% to ‒9.4%). Among women who had received 1 dose, the decrease was statistically significant for HPV-16 at ‒8.9 (95% CI = ‒14.2% to ‒3.1%) but nonsignificant for HPV-18. Geometric mean concentration ratios of 3:1 dose (year 16) were 3.0 and 2.2 for HPV-16 and HPV-18, respectively. HPV-16/18 seropositivity remained exceedingly high 16 years after vaccination. Over 5 years, small declines in antibodies were observed. Women should have protection for at least 20 years and likely much longer at the observed rate of decline.

Study on Coal Seam Roof Failure Based on Optical Fiber Acoustic Sensing and the Parallel Electrical Method

As China enters the stage of deep coal mining, the accidents caused by roof failure pose increasingly serious threats. Current research on roof failure zones often use single methods, but single geophysical data may result in multisolution issues during interpretation. This paper employed similar simulation experiments, exploring the strain failure characteristics and the changes in apparent resistivity caused by stress variations, taking the 11-3106 working face of a mining area as the research object. Through optical fiber strain and apparent resistivity, the locations and degrees of fracture in postmining rock strata were identified. The feasibility of using distributed optical fiber sensing and the parallel electrical method for qualitative and quantitative analysis of mining-induced fractures was verified. The results showed that optical fiber strain increased significantly at the location of rock fracture, with apparent resistivity anomalies rising correspondingly. The peak strain region corresponded well with the region of apparent resistivity anomalies. In a similar simulation with a geometric ratio of 1:100, the height of the caving zone was measured to be 31.65 cm, with a caving-to-mining ratio of 6.33. In the field working face, the caving zone height was 29.47 m, with a caving-to-mining ratio of 6.01, consistent with the actual conditions of the 11-3106 working face.

Influence of submerged impingement jet designs on solar air collector performance

The present study experimentally investigates the solar air heater performance employing submerged impinging jets (SAHSIJ). The submerged jets produce high flow velocities, leading to significant turbulence aided by shear forces at the heated surface, resulting in increased and evenly distributed heat removal rates. The study explores the impact of geometric parameters viz jet spacing ratio (Sj/Dh) from 0.108 to 0.433, jet angles (α) from 75° to 90° jet diameter ratio (d/Dh) from 0.043 to 0.076, span-wise pitch ratio (Y/Dh) from 0.43 to 1.08 and stream wise pitch (X/Dh) from 0.43 to 1.73 on the Nusselt number and friction performance to enhance the overall efficacy of the system. To evaluate the effectiveness of the new SAHSIJ design in terms of thermal and thermo-hydraulic performance, the results are compared with those from a smooth duct solar air heater. The results show that the novel solar air heater with submerged pipe jet significantly outperforms the smooth duct solar air heater in terms of heat removal from the absorber plate. SAHSIJ achieved a thermal efficiency (ηth) of 75.3 % and a thermo-hydraulic efficiency (ηeff) of 69.2 %, with a thermo-hydraulic performance parameter (η) of 3.19.