Experimental Simulation Research Articles

Tunable Chiroptical Activity in Branched Ag@Au Nanoparticles with Molecular Chirality and Geometric Chirality.

Chiral plasmonic nanomaterials have attracted significant awareness due to their applications in chiral catalysis, biosensing, photonics, and separation. Constructing plasmonic core-shell nanomaterials with geometric chirality and desirable optical chirality is a crucial yet challenging task for extending the range of chiral plasmonic nanomaterials. Here, a two-step method is reported for the synthesis of Gold (Au) branches wrapped silver (Ag) nanocubes (L/DBAg@Au) with strong and tunable circular dichroism (CD) signals under the regulation of L/D-cysteine (L/D-Cys). The Au branches consisted of multiple pinwheel-like Au. Both experimental results and theoretical simulations have demonstrated that the CD signals of these structures originated from the synergism between molecular chirality and geometrical chirality. The CD signals in the visible region could be enhanced through coupling effects between Au and Ag. The CD signals and geometries evolved with the variations in Cys concentration, chiral molecule type, and incubation time. This work provides valuable insights to guide the rational design of plasmonic core-shell nanomaterials with geometric chirality.

Reactive changes in dental tissues in response to curing light exposure: An experimental study

BACKGROUND: The use of curing lamps has considerably improved the quality of dental treatment. Curing light exposure protocols are primarily based on the effectiveness (completeness) of cure. The risk of heat impact on the dental pulp and surrounding tissues is a downside of curing light radiation. There is a need for experimental confirmation of differentiated selection of curing light exposure protocols (intensity and time of exposure) in terms of minimum impact on tissues. AIM: To assess the effect of curing light on dental tissues. MATERIALS AND METHODS: An experimental simulation of the use of curing light in dental practice during dental restoration was performed. The experiment was performed in 50 rats randomized into four groups: Group 1 (control, n=5) and Groups 2–4 (treatment, n=15 each). The control group was not exposed to curing light. In the treatment groups, mandibular incisors of the experimental animals were exposed to curing light in three modes. The animals were sacrificed by decapitation after 7 days in Group 1 and after 1, 3, and 7 days in Groups 2–4. A total of 100 teeth were extracted for pathomorphological examination. A total of 320 histological sections (enamel, dentin, and pulp slides) were prepared, stained, and examined. The descriptive method was used to assess the findings. RESULTS: Changes in the pulp showed pathomorphological signs of acute inflammation, most prominent on Day 3, which was considered a defense response of the pulp to irritation. The microvasculature showed the most significant changes, with increased, inhomogeneous blood filling, plasmorrhagia of capillary walls, and stasis in capillary lumen. There were no morphological changes in hard dental tissues. The initial response of the dental pulp to curing light exposure in experimental animals was uniform and unaffected by the technical specifications of curing lamps. On Day 7, there was no morphological response in the pulp when exposed to diode light at 1,000 and 1,400 mW/cm2. At this point, the microscopic appearance of the pulp exposed to diode curing light at 3,200 mW/cm2 was generally comparable to that at baseline, with residual perivascular cellular infiltration of the stroma and capillary congestion. CONCLUSION: The experimental findings indicate a risk of negative photochemical reactions in the pulp following curing light exposure during treatment of patients with hard dental tissue pathologies. The data on the effect of curing light on the dental pulp can be used in real-world dental practice when selecting a composite curing algorithm during dental restoration to reduce the risk of unexpected reactions to curing light.

Influence of Iodine Chemistry in I2 Scrubbing Modeling

With the scrubbing of molecular iodine (I2) from gas streams in water pools at an accident site (boiling water reactor wetwell, filtered containment venting systems, etc.), some discernible impact of the aqueous radiochemistry on the I2 decontamination factor (DF) is expected, sometimes with hardly any effect on aerosol scrubbing. In the frame of the NUGENIA Integration of Pool Scrubbing Research to Enhance Source-Term Calculations (IPRESCA) project, the Central Research Institute of Electric Power Industry (CRIEPI) in Japan performed a series of tests to study the I2 scrubbing behavior at high pH values, with changing pH in the course of the tests. We used these data for our simulation analyses, and we obtained sensible estimates of the experimental DF values in many calculated cases. The employed tool for our simulations was a modified version of the SPARC code inside MELCOR. This program was used for the IPRESCA benchmark parametric calculations, where the pH-dependent effect of the iodine chemistry equilibria at the bubble-water interface was predicted to be significant. The same was true for our simulations in the CRIEPI experiments. We have now modeled not just the interface equilibria, but also some slower (kinetic-driven) chemical interactions in water, which would transform, at these high pH values, most of the I2 into nonvolatile aqueous iodine species. The overall chemistry effect is quite pronounced, like in the experiments, though the description of the bubble thermal hydraulics was at least of the same importance for modeling. Many open questions remain, one of the trickiest of which being the employment of radiochemistry models (relevant to real accident conditions) for explanations of experiments driven by the normal (thermal) chemistry of iodine.

A Smart Contract-Based Algorithm for Offline UAV Task Collaboration: A New Solution for Managing Communication Interruptions

Environmental factors and electronic interference often disrupt communication between UAV swarms and ground control centers, requiring UAVs to complete missions autonomously in offline conditions. However, current coordination schemes for UAV swarms heavily depend on ground control, lacking robust mechanisms for offline task allocation and coordination, which compromises efficiency and security in disconnected settings. This limitation is especially critical for complex missions, such as rescue or attack operations, underscoring the need for a solution that ensures both mission continuity and communication security. To address these challenges, this paper proposes an offline task-coordination algorithm based on blockchain smart contracts. This algorithm integrates task allocation, resource scheduling, and coordination strategies directly into smart contracts, allowing UAV swarms to autonomously make decisions and coordinate tasks while offline. Experimental simulations confirm that the proposed algorithm effectively coordinates tasks and maintains communication security in offline states, significantly enhancing the swarm’s autonomous performance in complex, dynamic scenarios.

An Exploration of Groundwater Resource Ecosystem Service Sustainability: A System Dynamics Case Study in Texas, USA

Groundwater, a crucial natural resource on a global scale, plays a significant role in Texas, impacting various essential ecosystem services either directly or indirectly. Despite efforts of state- and community-level regulations and conservation efforts, there is an ongoing trend of declining groundwater levels in the state of Texas. In this study, we utilized the systems thinking and system dynamics modeling approach to better understand this problem and investigate possible leverage points to achieve more sustainable groundwater resource levels. After conceptualizing a causal loop diagram (CLD) of the underlying feedback structure of the issue (informed by the existing literature), a small system dynamics (SD) model was developed to connect the feedback factors identified in the CLD to the stocks (groundwater level) and flows (recharge rate and groundwater pumping) that steer the behaviors of groundwater systems across time. After completing model assessment, experimental simulations were conducted to evaluate the current state relative to simulated treatments for improved irrigation efficiency, restricted pumping rates, cooperative conservation protocols among users, and combination strategy (of all treatments above) in the long-term. Results showed that groundwater stress (and the associated repercussions on related ecosystem service) could be alleviated with a combination strategy, albeit without complete groundwater level recovery.

Optimally Miscible Polymer Bulk-Heterojunction-Particles for Nonsurfactant Photocatalytic Hydrogen Evolution.

Mini-emulsion and nanoprecipitation techniques relied on large amounts of surfactants, and unresolved miscibility issues of heterojunction materials limited their efficiency and applicability in the past. Through our molecular design and developed surfactant-free precipitation method, we successfully fabricated the best miscible bulk-heterojunction-particles (BHJP) ever achieved, using donor (PS) and acceptor (PSOS) polymers. The structural similarity ensures optimal miscibility, as supported by the interaction parameter of the PS/PSOS blend is positioned very close to the binodal curve. Experimental studies and molecular dynamics simulations further revealed that surfactants hinder electron output sites and reduce the concentration of sacrificial agents at the interface, slowing polaron formation. Multiscale experiments verified that these BHJP, approximately 12 nm in diameter, further form cross-linked fractal networks of several hundred nanometers. Transient absorption spectroscopy showed that BHJP facilitates polaron formation and electron transfer. Our BHJP demonstrated a superior hydrogen evolution rate (HER) compared to traditional methods. The most active BHJP achieved an HER of 251.2 mmol h-1 g-1 and an apparent quantum yield of 26.2% at 500 nm. This work not only introduces a practical method for preparing BHJP but also offers a new direction for the development of heterojunction materials.

The Effectiveness of Local Exhaust Ventilation (LEV) System in Welding Training Facilities using Validation Computational Fluid Dynamics (CFD) Simulation

The Local Exhaust Ventilation (LEV) is the most common type of engineering control equipment used to control employees' exposure to chemicals that are hazardous to their health. Before a contaminant disperses into the workroom environment, LEV systems operate on the principle of capturing it at or near its source. The welding guideline stated that the suggested minimum hood velocity is 100 ft/min, the recommended velocity along ducts for vapors, gases, and smoke is 1000 ft/min, and 2000 ft/min. The research objective is to identify the effectiveness of the LEV system using validation computational fluid dynamics (CFD) simulation. The data collected by experimental design during the pre-testing phase of the LEV system is quantitative and obtained through a fieldwork survey and document analysis. Findings found that LEV systems are effective to be used and meet all the minimum requirements set by the guideline. In CFD simulation, upon validation, the average absolute error obtained from the case study is 8.4%. There is good agreement between actual experimental and CFD simulation results, and the acceptable validity of CFD simulation is less than 10%. Therefore, simple CFD modeling is a tool to simulate air velocity in the LEV system, saving labor costs and time consumption during the earliest stage of LEV design development before actual construction. This study's outcome can serve as a benchmark or guideline for training facilities equipped with the LEV system to prioritize safety and health.

Integration of the patient partner in simulation-based learning in initial pharmacy training

Background: Over the years, role-playing simulations have gradually become part of pharmacy teaching. The aim of this study is to characterise the potential of the patient partner, in relation to the student and the teacher, to interpret the role of the patient and to carry out the debriefing during role-playing simulations of pharmaceutical dispensing. Methods: Experimental simulations were set up to compare students, patient partners and teachers in the role of patient. Each simulation was subject to observations (n = 30) focusing on the quality of the role plays and debriefings performed. Results: In addition to the realism provided, the patient partner showed the greatest adaptability in their roles of his role, able to both make more complex and simplify the situation according to the student's needs. Regarding the debriefing, the teacher seemed to be the one most able to detect the points of improvement in the performance achieved regarding communication and pharmaceutical skills. Conclusion: Students, teachers or patient partners bring different resources that should be used thoughtfully by teachers according to the educational objectives of the simulation. However, it is important to be aware that the ability of the patient partners to participate in such lessons depends on their training and experience.

Scalable Reshaping of Diamond Particles via Programmable Nanosculpting.

Diamond particles have many interesting properties and possible applications. However, producing diamond particles with well-defined shapes on a large scale is challenging because diamonds are chemically inert and extremely hard. Here, we show that air oxidation, a routine method for purifying diamonds, can be used to precisely shape diamond particles at scale. By exploiting the distinct reactivities of different crystal facets and defects inside the diamond, layer-by-layer outward-to-inward and inward-to-outward oxidation produced diverse diamond shapes including spheres, twisted surfaces, pyramidal islands, inverted pyramids, nanoflowers, and porous polygons. The nanosculpted diamonds had more and finer features that enabled them to outperform the original raw diamonds in various applications. Using experimental observations and Monte Carlo simulations, we built a shape library that guides the design and fabrication of diamond particles with well-defined features that could be critical for anticounterfeiting, optical, and other practical applications. Our study presents a simple, economical, and scalable way to produce shape-customized diamonds for various potential technologies.

Investigation of electromagnetic wave propagation characteristics across various frequencies in porous media of goaf.

The reliable long-distance transmission of electromagnetic wave signals within goaf is fundamental for the implementation of wireless monitoring and early warning systems for goaf-related disasters. This paper establishes an experimental platform for electromagnetic wave signal transmission within goaf and develops a propagation model for electromagnetic waves in the porous media of goaf. The transmission characteristics of electromagnetic waves at various frequencies within the porous media environment of goaf are investigated through experimental and numerical simulation approaches. The results indicate that the received signal intensity of electromagnetic waves across different frequency bands diminishes with increasing propagation distance in the lossy environment of the goaf. Initially, the decay follows a logarithmic pattern, whereas, at later stages, the attenuation exhibits a gradual and smooth decrease. As the frequency increases, the initial attenuation amplitude of electromagnetic wave intensity rises; however, subsequent attenuation is largely unaffected by frequency, with the later attenuation rate being proportional to porosity. Electromagnetic waves at a frequency of 700 MHz exhibit a low attenuation coefficient under both experimental and simulated conditions, demonstrating superior stability and reliability. This frequency significantly enhances the overall performance of the communication system and is suitable for use as the operational frequency band in wireless sensor networks.

Trap Density Estimation for TDDB Testing in SiC Power MOSFETs

Abstract The trap density estimation of SiC power MOSFET in time-dependent dielectric breakdown (TDDB) was investigated by using experiment and TCAD simulation. The gate leakage current (IGSS) under negative voltage was measured and a current spike was found which was linearly shifted with TDDB stress. Based on four-state nonradiative multi phonon (NMP) defect capture model, the mechanism and modeling of IGSS current spike was studied. Based on TCAD simulation, the characteristics of gate oxygen donor traps including trap energy level, trap density, and position distribution were estimated, and the trap density model in TDDB experiment was proposed and verified. This study may contribute to the estimation of trap density in SiC MOSFET.

Numerical simulation and experimental investigation of the propagation law of plasma pulse shock waves

Abstract Plasma pulse shock wave rock-breaking technology represents a novel approach to rock fracturing. Present research on this subject largely addresses rocks and electrodes, yet often neglects the critical influence of shock waves in the rock-breaking process. Therefore, it is necessary to further study the propagation law of the shock wave and its reflection and transmission. This paper undertakes experimental simulations using the RHT rock model to explore the propagation process of plasma pulse shock waves based on two variables: the medium and the shape of the electrode. Integrated with one-dimensional stress wave theory, the study examines the impact of four specific parameters—dielectric thickness, surrounding rock height, surrounding rock density, and surrounding rock porosity—on the reflection and transmission rates of shock waves. Pressure data collected from experimental platform are utilized to validate the study’s conclusions. The findings indicate that the propagation behaviors of shock waves differ significantly between water and air mediums. The shape of the electrode causes significant differences in the pressure exerted by the shock wave at the same location. Both the thickness of the dielectric and the porosity of the surrounding rock show a positive correlation with the reflection coefficient and a negative correlation with the transmission coefficient, while the density of the surrounding rock exhibits an inverse relationship. The height of the surrounding rock is irrelevant to both reflection and transmission coefficients.

Development of a Scaled Down Test-Rig for Wheel–Rail Contact Thermal Experiments Using Optical Sensors

Abstract Rail wheel contact measurement is crucial for several reasons. First and foremost, it directly affects the safety of passengers, crew, and the general public. Accurate measurements help identify irregularities in wheel-rail contact, such as wheel defects, wear, or track anomalies, which can lead to derailments or accidents if left unaddressed. An inventive technique for measuring the temperatures at rail wheel contact at various speeds is presented in this research. The novel approach uses a 1:5 scaled-down test rig model of a wheel and rail with Fiber Bragg Grating (FBG) sensor to combine the experimental and finite element analysis simulation to determine the rail wheel contact temperature. By employing the various data acquisition and data analysis techniques rail wheel contact temperature at different speeds ranging between 10kmph to 40kmph was determined 1538.735 nm to 1538.831nm with centre wavelength of 1538.438 nm. The results illustrate the possibilities of the downsized test rig with experimental observations at varying speeds by examining the benefits of FBG sensors over traditional sensors. The experimental results are used to determine the equivalent wavelength shift. Fibre Bragg Grating (FBG) sensor design and simulation are done with the Grating MOD optical tool. For this temperature range and Bragg's wavelength of 1538.438 nm, the sensitivity of Fiber Bragg Grating is observed to be 13.6pm/°c.

Tunable mechanical performance of nanoporous energy absorption composite material

Abstract Nanofluidic energy absorption materials (NEAs) represent smart and efficient energy absorption composite materials in the ever-growing application of advanced protective structures. In this paper, an integrated experimental and molecular dynamics simulation study is conducted on the NEAs (ZSM-5/water) to investigate the tunable strategy of mechanical performance and energy absorption by considering the microstructural, mechanical, and thermal factors. The results demonstrate that the NEAs is an efficient and tunable liquid spring-like volume memory material. The typical NEAs show superior energy absorption capacity, achieving a specific energy absorption of 5.17 J/cm³ and an energy absorption ratio of 1.14 J/cm³ per cycle. Compared with insensitivity of the loading rate, the solid-fluid mass ratio is confirmed to significantly affect energy absorption performance, with an optimal ratio of approximate 1. Temperature is validated as an effective in-situ tunable parameter for NEAs in terms of both infiltration and energy absorption properties, with only slight effect on exfiltration. The critical infiltration pressure and specific energy absorption decrease by 23% and 40% as temperature increase from 25°C to 80°C. The gas-fluid interaction based energy absorption mechanism under high temperatures is proposed according to the comparison between experimental results and molecular dynamics simulations. The findings in this work will provide novel materials solutions for the intelligent energy absorption protective structures.

MATHEMATICAL MODELING AND ANALYSIS OF DYNAMIC CHARACTERISTICS OF A BRUSHLESS MOTOR IN AUTOMATED CONTROL SYSTEMS

The article provides a detailed analysis of brushless motors (BM) within the context of automated control, focusing on dynamic modes and mathematical modeling of the electric drive. It addresses the dynamic characteristics, transfer function development, and specific operational aspects of BM in systems with regulated rotational speed. The article presents experimental data and computer simulation results that validate the effectiveness of the selected models. Experimental studies conducted on a laboratory model confirm the accuracy of the developed mathematical model, particularly demonstrating the feasibility of approximating the motor's transfer function in a linear form to simplify control system analysis and tuning. Computer simulations are conducted in MATLAB using SIMULINK, which enables precise and illustrative visualization of transient processes in the BM. The article also introduces a subordinate control principle within a closed-loop control system, which ensures control stability and accuracy by dividing into speed and current loops. The simulation results demonstrate the potential of utilizing the developed models for further research and the design of efficient and reliable control systems for brushless motors in industrial settings. The proposed modeling approach paves the way for the creation of energy-efficient electric drives with high-precision control.

Combined Experimental and Molecular Simulation Characterization of CO2 Adsorption Characteristics of Full Aperture in Bituminous Coal Pores

Combined Experimental and Molecular Simulation Characterization of CO₂ Adsorption Characteristics of Full Aperture in Bituminous Coal Pores

Molecular dynamics and experimental study of mechanical and tribological properties of graphene‐reinforced nitrile butadiene rubber–phenolic resin composites

AbstractThe mechanical and tribological properties as well as the microstructural characteristics of five groups of nitrile butadiene rubber (NBR)/graphene (GE)/phenolic resin (PF) composites were systematically investigated using a combination of experimental and molecular dynamics (MD) simulation methods. Experiments confirmed that PF effectively enhanced the mechanical properties of NBR, including the crosslinking density, hardness, and compression permanent deformation, along with its tribological performance under various working conditions. MD simulations further clarified the tribological mechanism of the NBR/GE/PF composites from a microscopic perspective, highlighting the pivotal role of the hydrogen‐bonding network. PF15 exhibited low wear and mobility during friction owing to its robust hydrogen‐bonding network.Highlights Combined experiments and simulation for NBR performance analysis. Investigated the tribological properties of NBR/GE/PF under various conditions. Hydrogen bonding in NBR/GE/PF was achieved via simulation. A good correlation was found between experimental results and simulation data.

Aerodynamic investigation by experimental and computational simulation of a flying wing unmanned aerial vehicle for cargo delivery and surveillance missions

Baseline-IX is a tailless aircraft design with compound wing attached to a short body, a transition between a straight, swept flying wing design and a blended wing-body. Baseline-IX planform was designed to deal with a small BWB UAV that is capable of cargo delivery and surveillance missions. The design is influenced by the requirement of cargo space to carry batteries medical and other emergency supplies in its fuselage with a nose-mounted mission camera with a wingspan under 2.0 meters. This paper focuses on studying the aerodynamic characteristics of the novel Baseline-IX, inspired by its predecessor, the Baseline-V. Aerodynamic characteristics of Baseline-IX were investigated and validated through numerical computational simulations and wind tunnel experiments. The maximum lift-to-drag ratio of Baseline-IX obtained through this study is 15.14 for 1:2.4 scaled model and 17.46 for 1:1 prototype. Numerical simulation and wind tunnel experiments’ lift-to-drag ratio percentage difference is 4.92%. Baseline-IX’s lift-to-drag ratio surpasses 14.09% and 24.28% over similar-missions UAV operating in the market while both are larger in size. Baseline-IX has the potential to be developed as a small, easy to carry cargo delivery and surveillance BWB UAV.

Research on the Wear Suppression of Diamond Grain Enabled by Hexagonal Boron Nitride in Grinding Cast Steel.

Diamond grinding wheels have been widely used to remove the residual features of cast parts, such as parting lines and pouring risers. However, diamond grains are prone to chemical wear as a result of their strong interaction with ferrous metals. To mitigate this wear, this study proposes the use of a novel water-based hexagonal boron nitride (hBN) as a minimum quantity lubrication (MQL) during the grinding of cast steel and conducted the grinding experiment and molecular dynamics simulation. The experiment demonstrated that compared to dry grinding, the water-based hBN nanofluid can effectively reduce the maximum temperature of a workpiece at contact zone from 408 K to 335 K and change the serious abrasion wear of diamond grain to slightly micro-broken. The molecular dynamics simulation indicates that the flake of hBN can weaken the catalytic effect of iron on the diamond, prevent the diffusion of carbon atom to cast steel, and suppress the graphitization of diamond grain. Additionally, the flake of hBN improves the contact state between the diamond grain and cast steel and reduces the cutting heat and friction coefficient from about 0.5 to 0.25. Thus, the water-based hBN nanofluid as a new MQL was proven to be suitable for the wear inhibition of diamond grain when grinding cast steel.

Slot Occupancy-Based Collision Avoidance Algorithm for Very-High-Frequency Data Exchange System Network in Maritime Internet of Things

The maritime industry is undergoing a paradigm shift driven by rapid advancements in wireless communication and an increase in maritime traffic data. However, the existing automatic identification system (AIS) struggles to accommodate the increasing maritime traffic data, leading to the introduction of the very-high-frequency (VHF) data exchange system (VDES). While the VDES increases bandwidth and data rates, ensuring the stable transmission of maritime IoT (MIoT) application data in congested coastal areas remains a challenge due to frequent collisions of AIS messages. This paper presents a slot occupancy-based collision avoidance algorithm (SOCA) for a VDES network in the MIoT. SOCA is designed to mitigate the impact of interference caused by transmissions of AIS messages on transmissions of VDE-Terrestrial (VDE-TER) data in coastal areas. To this end, SOCA provides four steps: (1) construction of the neighbor information table (NIT) and VDES frame maps, (2) construction of the candidate slot list, (3) TDMA channel selection, and (4) slot selection for collision avoidance. SOCA operates by constructing the NIT based on AIS messages to estimate the transmission intervals of AIS messages and updating VDES frame maps upon receiving VDES messages to monitor slot usage dynamically. After that, it generates a candidate slot list for VDE-TER channels, classifying the slots into interference and non-interference categories. SOCA then selects a TDMA channel that minimizes AIS interference and allocates slots with low expected occupancy probabilities to avoid collisions. To evaluate the performance of SOCA, we conducted experimental simulations under static and dynamic ship scenarios. In the static ship scenario, SOCA outperforms the existing VDES, achieving improvements of 13.58% in aggregate throughput, 11.50% in average latency, 33.60% in collision ratio, and 22.64% in packet delivery ratio. Similarly, in the dynamic ship scenario, SOCA demonstrates improvements of 7.30%, 11.99%, 39.27%, and 11.82% in the same metrics, respectively.