Physical Surrogate Research Articles

Neck stiffness and range of motion for young males and females

Well characterised mechanical response of the normal head-neck complex during passive motion is important to inform and verify physical surrogate and computational models of the human neck, and to inform normal baseline for clinical assessments. For 10 male and 10 female participants aged 20 to 29, the range of motion (ROM) of the neck about three anatomical axes was evaluated in active-seated, passive-lying and active-lying configurations, and the neck stiffness was evaluated in passive-lying. Electromyographic signals from the agonist muscles, normalised to maximum voluntary contractions, were used to provide feedback during passive motions. The effect of sex and configuration on ROM, and the effect of sex on linear estimates of stiffness in three regions of the moment–angle curve, were assessed with linear mixed models and generalised linear models. There were no differences in male and female ROM across all motion directions and configurations. Flexion and axial rotation ROM were configuration dependent. The passive-lying moment–angle relationship was typically non-linear, with higher stiffness (slope) closer to end of ROM. When normalising the passive moment–angle curve to active lying ROM, passive stiffness was sex dependent only for lateral bending region 1 and 2. Aggregate moment–angle corridors were similar for males and females in flexion and extension, but exhibited a higher degree of variation in applied moment for males in lateral bending and axial rotation. These data provide the passive response of the neck to low rate bending and axial rotation angular displacement, which may be useful for computational and surrogate modelling of the human neck.

A Preliminary Step Towards a Physical Surrogate of the Human Calvarium to Model Fracture.

A surrogate model of the human calvarium can be used to assess skull-fracture-related head injuries without continuously requiring post-mortem human skulls. Skull simulants developed in the literature often require sophisticated manufacturing procedures and/or materials not always practical when factoring in time or expense considerations. This study's objective was to fabricate three exploratory surrogate models (1. pure epoxy prototype, 2. epoxy-chalk mix prototype, and 3. epoxy-chalk three-layered prototype) of the calvarium to mimic the calvarium's mechanical response at fracture using readily available and cost-effective materials, specifically epoxy and chalk. The surrogates and calvaria were subject to quasi-static and dynamic impact 4-point bending and their mechanical responses were compared statistically. Under quasi-static loading, all three surrogates showed a considerable number of differences in mechanical response variables to calvaria that was deemed significant (p < 0.05). Under dynamic impact loading, there was no sufficient evidence to reject that the average mechanical response variables were equal between the epoxy-chalk three-layered prototype and calvaria (p > 0.05). This included force and bending moment at fracture, tensile strain at fracture, tensile and compressive stress at fracture, tensile modulus, and tensile strain rate. Overall, our study illustrates two main remarks: (1) the three exploratory surrogate models are potential candidates for mimicking the mechanical response of the calvarium at fracture during impact loading and (2) employing epoxy and chalk, which are readily available and cost-effective has the potential to mimic the mechanical response of calvaria in impact loading.

A new biomechanical FE model for blunt thoracic impact.

In the field of biomechanics, numerical procedures can be used to understand complex phenomena that cannot be analyzed with experimental setups. The use of experimental data from human cadavers can present ethical issues that can be avoided by utilizing biofidelic models. Biofidelic models have been shown to have far-reaching benefits, particularly in evaluating the effectiveness of protective devices such as body armors. For instance, numerical twins coupled with a biomechanical model can be used to assess the efficacy of protective devices against intense external forces. Similarly, the use of human body surrogates in experimental studies has allowed for biomechanical studies, as demonstrated by the development of crash test dummies that are commonly used in automotive testing. This study proposes using numerical procedures and simplifying the structure of an existing biofidelic FE model of the human thorax as a preliminary step in building a physical surrogate. A reverse engineering method was used to ensure the use of manufacturable materials, which resulted in a FE model called SurHUByx FEM (Surrogate HUByx Finite Element Model, with HUByx being the original thorax FE model developed previously). This new simplified model was validated against existing experimental data on cadavers in the context of ballistic impact. SurHUByx FEM, with its new material properties of manufacturable materials, demonstrated consistent behavior with the corresponding biomechanical corridors derived from these experiments. The validation process of this new simplified FE model yielded satisfactory results and is the first step towards the development of its physical twin using manufacturable materials.

Derivation and Experimental Validation of the Equations of Motion of Magnetic Pendulums

Abstract A series of coaxial magnetic pendulums is studied as a simple physical surrogate for more general nonlinearly coupled almost-identical resonators that arise in quantum communications and the dynamics of social networks. The equations of motion for a series of coaxial magnetic pendulums are derived, and the solution is compared to experimental results. The equilibrium points and their stability are also determined.

Repeatability and Biofidelity of a Physical Surrogate Neck Model Fit to a Hybrid III Head.

In helmet impact testing, parameters including acceleration and velocity are measured using instrumented head-neck models that are meant to be mechanically realistic (i.e. biofidelic) stand-ins, or surrogates, for humans. Currently available models of the human neck are designed primarily for application in automotive crash testing, and their applicability in assessment of helmets is often questioned. The object of the present work is to document the mechanical design, repeatability, and biofidelity in low speed impact of a new neck model that we apply with a Hybrid III head. Focusing on Hybrid III head kinematics measured during impacts at 2 to 6 m/s, the co-efficient of variance of repeated measures of kinematics was generally less than 10%. Differences in kinematics between identical copies of the neck was less than 20% when tested with helmets, and less than 7% when the head was not helmeted. In parallel testing using a Hybrid III head-neck, the co-efficient of variance in repeated measures was less than 4% and the kinematics significantly differed from those measured using the new neck. CORAplus scores for the new neck were approximately 0.70 when compared against data for human subjects with passive neck muscles experiencing impact at 2 m/s.

A Computational Investigation of Fuel Chemical and Physical Properties Effects on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine

Gasoline compression ignition (GCI) offers the potential to reduce criteria pollutants while achieving high fuel efficiency. This study aims to investigate the fuel chemical and physical properties effects on GCI operation in a heavy-duty diesel engine through closed-cycle, three-dimensional (3D) computational fluid dynamic (CFD) combustion simulations, investigating both mixing-controlled combustion (MCC) at 18.9 compression ratio (CR) and partially premixed combustion (PPC) at 17.3 CR. For this work, fuel chemical properties were studied in terms of the primary reference fuel (PRF) number (0–91) and the octane sensitivity (0–6) while using a fixed fuel physical surrogate. For the fuel physical properties effects investigation, six physical properties were individually perturbed, varying from the gasoline to the diesel range. Combustion simulations were carried out at 1375 RPM and 10 bar brake specific mean pressure (BMEP). Reducing fuel reactivity was found to influence ignition delay time (IDT) more significantly for PPC than for MCC. 0D IDT calculations suggested that the fuel reactivity impact on IDT diminished with an increase in temperature. Moreover, higher reactivity gasolines exhibited stronger negative coefficient (NTC) behavior and their IDTs showed less sensitivity to temperature change. In addition, increasing octane sensitivity was observed to result in higher fuel reactivity and shorter IDT. Under both MCC and PPC, all six physical properties showed little impact on global combustion behavior, NOx, and fuel efficiency. Among the physical properties investigated, only density showed a notable effect on soot emissions. Increasing density led to higher soot due to deteriorated air entrainment into the spray and the slower fuel-air mixing process.

Mobility of maerl-siliciclastic mixtures: Impact of waves, currents and storm events

Maerl beds are free-living, non-geniculate coralline algae habitats which form biogenic reefs with high micro-scale complexity supporting a diversity and abundance of rare epifauna and epiflora. These habitats are highly mobile in shallow marine environments where substantial maerl beds co-exist with siliciclastic sediment, exemplified by our study site of Galway Bay. Coupled hydrodynamic-wave-sediment transport models have been used to explore the transport patterns of maerl-siliciclastic sediment during calm summer conditions and severe winter storms. The sediment distribution is strongly influenced by storm waves even in water depths greater than 100 m. Maerl is present at the periphery of wave-induced residual current gyres during storm conditions. A combined wave-current Sediment Mobility Index during storm conditions shows correlation with multibeam backscatter and surficial sediment distribution. A combined wave-current Mobilization Frequency Index during storm conditions acts as a physical surrogate for the presence of maerl-siliciclastic mixtures in Galway Bay. Both indices can provide useful integrated oceanographic and sediment information to complement coupled numerical hydrodynamic, sediment transport and erosion-deposition models.

Image Analysis of a Fluorescent Physical Surrogate for Quantifying Listeria monocytogenes Transfer between Delicatessen Meats and Product Contact Surfaces

Abstract. is the primary pathogen of concern for microbial safety of delicatessen meats sliced at retail. A fluorescent powder (Glo GermTM, GGP) has been used previously to qualitatively assess cleaning and hand washing practices in foodservice. However, quantitative use of this material as a physical surrogate for transfer would enable direct evaluation of training intervention programs and validation of existing risk models. The objective was to develop a method to quantify the spread of GGP between delicatessen meats (turkey and ham) and product contact surfaces [stainless steel (SS) and high density polyethylene (HDPE)], then mathematically relate these findings to the rate of transfer under equivalent conditions. A six-strain cocktail was inoculated onto 8 x 8 cm pieces of delicatessen roast turkey (T), ham (H), grade 304 SS, or HDPE, at ~109 CFU/cm2, and allowed to surface dry. Inoculated T, H, SS, or HPDE was placed in contact with an uninoculated surface of an opposite type for 3 s at room temperature, with additional normal force, for 12 sequential contact events on 12 separate surfaces. This same procedure was repeated using a suspension of GGP in 70% ethanol (1:10). Listeria populations were quantified by plating stomached (T, H) or sonicated (SS, HDPE) dilutions on modified Oxford agar. GGP-contacted surfaces were photographed under controlled UV-light and quantitatively analyzed via image processing software. Results showed a logarithmic transfer response for both and GGP. The GGP data for each transfer scenario were fit to the corresponding data by minimizing the root mean squared error (RMSE) between the two curves using an offset and multiplier. Because the parameters for T, H, SS, and HPDE differed significantly (P

Sense of Touch in Training Tasks Demanding High Precision and Short Time of Execution

Engaging the sense of touch in virtual environments is a challenging and important issue. Currently, the most common way to address this issue is the use of a set of actuators that restrict hand movement. This article presents an alternative method to track physical surrogate representations of virtual objects using a vision-based system. Using real objects that can be manipulated by a person immersed in a virtual environment is an alternative to expensive robotized haptic systems. Moreover, this technique allows the user to move objects over long distances. Research conducted with 30 volunteers shows that the sense of touch can significantly reduce the execution time of tasks demanding high precision. Despite this decrease in execution time, an increase in precision has been observed. The conclusion of this article looks at the pros and cons of the use of physical surrogates for virtual objects, for example, less time needed for virtual reality-based training with the use of physical surrogates.

A combustion model for multi-component fuels using a physical surrogate group chemistry representation (PSGCR)

A combustion model to simulate the oxidation of multi-component fuels has been developed and applied to model autoignition combustion processes. The model is called the Physical Surrogate Group Chemistry Representation (PSGCR) method, which combines a multi-component fuel model to describe the physical properties of the fuel with reduced reaction mechanisms to represent the chemistry of the fuel components. A group of physical surrogate (PS) components are used to describe the fuel’s physical properties, such as the distillation profile, specific gravity, lower heating value and hydrogen-to-carbon (H/C) ratio. The oxidation processes of the fuel are modeled using skeletal reaction mechanisms for a group of chemical surrogate (CS) components that employ generic reactions as well as detailed reaction kinetics. The generic reactions were built to model unavailable reaction pathways from physical surrogates to the base CS components or their intermediate species. The model includes the 6 major chemical classes of typical hydrocarbon fuels, i.e., n-paraffins, iso-paraffins, olefins, naphthenes, aromatics and oxygenates, and 65 representative hydrocarbon components are included in a data base for the physical surrogate components and 43 chemical surrogate components are considered for the group chemistry representation. Six types of generic reaction sets are proposed to model the oxidation of 15 physical surrogate components that are called extended-CS (chemical surrogate) components. The present generic reactions are modeled such that the major characteristics of the oxidation process of the fuel components are included in a consistent manner.The final version of the PSGCR reaction mechanism consists of 264 species and 1292 reactions. Validation of the reaction mechanisms was performed by comparing predicted ignition delay times with experimental measurements and/or predictions from comprehensive mechanisms available in the literature. The model was also validated against HCCI experimental data of the FACE fuels. Then the model was applied to simulate practical diesel fuel (F76) spray combustion in a constant volume chamber, and the predicted ignition delay times of the surrogate model fuel were compared with measured values. The results show that the present PSGCR method captures the combustion characteristics of complex multi-component fuels, giving reliable performance for combustion predictions, as well as computational efficiency improvements for multi-dimensional CFD simulations through the use of reduced mechanisms.

A method to reduce design complexity of automotive composite structures with respect to crashworthiness

Composites in automotive structures show great promise to further improve vehicle crashworthiness. However, designing automotive structures for crash with advanced composite materials is challenging. The large amount of design parameters for laminated composites, the complex non-linear material behavior and the discontinuous design space in vehicle design, such for crashworthiness, are the main contributors to this challenge. In this paper, we propose a new design strategy to address this and integrate advanced laminated composite materials in automotive design for crashworthiness. First a computationally efficient physical surrogate is introduced to predict the structural validity of the design options and filter the design space. Secondly a method is introduced which uses Sobol decomposition to derive a design parameter importance hierarchy. Thirdly the physical surrogate is used to derive parameter bounds to increase robustness. A typical S-rail benchmark has been developed to confirm the usefulness of the proposed method. Finally the method provides for a reduced and robust design space which may help to decrease early development time.

Diffusive gradient in thin films technique for assessment of cadmium and copper bioaccessibility to radish (Raphanus sativus)

The aim of this study was to assess cadmium and copper uptake by radish (Raphanus sativus) and to test the capability of the diffusive gradient in thin films (DGT) technique to predict bioaccessibility of the metals for this plant. Radish plants were grown in pots filled with uncontaminated control and artificially contaminated soils differing in cadmium and copper contents. Metal concentrations in plants were compared with free ion metal concentrations in soil solution, and concentrations measured by DGT. Significant correlation was found between metal fluxes to plant and metal fluxes into DGT. Pearson correlation coefficient for cadmium was 0.994 and for copper 0.998. The obtained results showed that DGT offers the possibility of simple test procedure for soils and can be used as a physical surrogate for plant uptake.

Effective Modeling of Conjugate Heat Transfer and Hydraulics for the Regenerative Cooling Design of Kerosene Rocket Engines

The present work is motivated to develop a unified framework to simulate multi-physical processes which are crucial for trade-off design of liquid rocket thrust chambers among propulsive performance, regenerative cooling, and pressure budget. In this paper, an effective modeling of conjugate heat transfer and hydraulics through the regenerative cooling passage has been performed to quantitatively evaluate detailed cooling designs, including spirally twisted channels and bidirectionally branched circuit, as well as to provide the wall heat flux to a compressible reacting flow solver in an interactively coupled manner. The kerosene fuel used as coolant is modeled by a three-component physical surrogate, and the fluid properties required for calculation of a Nusselt number correlation and empirical resistance coefficients are computed over the entire thermodynamic states from compressed liquid to supercritical fluid using the NIST SUPERTRAPP. The present method has been applied to an actual regeneratively cooled thrust chamber and validated against measurement of hot-firing tests in terms of temperature increase and pressure drop of the coolant through the cooling passages. Based on the numerical results, supplementary effects of peripheral fuel cooling injection and thermal barrier coating are addressed.

Physical Surrogate Leg to Evaluate Blast Mine Injury

Antipersonnel blast landmines pose a significant threat in affected areas, with injuries to the lower extremity and amputation being common. Addressing a need for injury prediction and protection evaluation, a 50th percentile physical surrogate lower leg was developed incorporating the load transmission paths in the lower leg. Biofidelic and frangible materials were evaluated and selected based on high deformation rate properties compared to those for human tissues. The predicted leg injuries from experimental blast testing were in agreement with injury data for unprotected and protected legs. Post-test examination was found to be the only consistent and reliable evaluation method for predicting injury outcome, and an evaluation based on tissue damage was shown to be sensitive to changes in loading conditions, not possible with existing approaches. This study identified the severity of calcaneal fracture as the primary determinant of serious injury, which should be the focus of future protection development.

Performance of a physical surrogate in the sequential approximate optimization of space trusses

PurposeThe purpose of this paper is to propose physically based varying fidelity surrogates to be used in structural design optimization of space trusses. The main aim is to demonstrate its efficiency in reducing the number of high fidelity (HF) runs in the optimization process.Design/methodology/approachIn this work, surrogate models are built for space truss structures. This study uses functional as well as physical surrogates. In the latter, a grid analogy of the space truss is used thereby reducing drastically the analysis cost. Global and local approaches are considered. The latter will require a globalization scheme (sequential approximate optimization (SAO)) to ensure convergence.FindingsPhysically based surrogates were proposed. Classical techniques, namely Taylor series and kriging, are also implemented for comparison purposes. A parameter study in kriging is necessary to select the best kriging model to be used as surrogate. A test case was considered for optimization and several surrogates were built. The CPU time is reduced when compared with the HF solution, for all surrogate‐based optimization performed. The best result was achieved combining the proposed physical model with additive corrections in a SAO strategy in which C1 continuity was imposed at each trust region center. Some guidance for other engineering applications was given.Originality/valueThis is the first time that physical‐based surrogates for optimum design of space truss systems are used in the SAO framework. Physical surrogates typically exhibit better generalization properties than other surrogates forms, produce faster solutions, and do not suffer from dimensionality curse when used in approximate optimization strategies.

Assessing Behind Armor Blunt Trauma (BABT) Under NIJ Standard-0101.04 Conditions Using Human Torso Models

Although soft armor vests serve to prevent penetrating wounds and dissipate impact energy, the potential of nonpenetrating injury to the thorax, termed behind armor blunt trauma, does exist. Currently, the ballistic resistance of personal body armor is determined by impacting a soft armor vest over a clay backing and measuring the resulting clay deformation as specified in National Institute of Justice (NIJ) Standard-0101.04. This research effort evaluated the efficacy of a physical Human Surrogate Torso Model (HSTM) as a device for determining thoracic response when exposed to impact conditions specified in the NIJ Standard. The HSTM was subjected to a series of ballistic impacts over the sternum and stomach. The pressure waves propagating through the torso were measured with sensors installed in the organs. A previously developed Human Torso Finite Element Model (HTFEM) was used to analyze the amount of tissue displacement during impact and compared with the amount of clay deformation predicted by a validated finite element model. All experiments and simulations were conducted at NIJ Standard test conditions. When normalized by the response at the lowest threat level (Level I), the clay deformations for the higher levels are relatively constant and range from 2.3 to 2.7 times that of the base threat level. However, the pressures in the HSTM increase with each test level and range from three to seven times greater than Level I depending on the organ. The results demonstrate the abilities of the HSTM to discriminate between threat levels, impact conditions, and impact locations. The HTFEM and HSTM are capable of realizing pressure and displacement differences because of the level of protection, surrounding tissue, and proximity to the impact point. The results of this research provide insight into the transfer of energy and pressure wave propagation during ballistic impacts using a physical surrogate and computational model of the human torso.

The nature of information

Starting from the definition of 'information' as a physical surrogate of knowledge (i.e. a spoken or written record), its relation to the originator, and its transformations on com munication to a recipient, and the recipient's mental state and possibly physical (social) reactions to it, are discussed. The transformations of 'information' in information retrieval systems are also considered. It is argued that this is the essen tial basis for developing a true information science.