Improvement in head blast-protection via the use of polyurea-augmented advanced combat helmet

2016 ◽  
Vol 7 (4) ◽  
pp. 516-552 ◽  
Author(s):  
Mica Grujicic ◽  
S Ramaswami ◽  
Jennifer Snipes ◽  
Ramin Yavari ◽  
Philip Dudt
Keyword(s):  
Interaction Analysis ◽  
Computational Study ◽  
Specific Impulse ◽  
Blast Mitigation ◽  
Content Type ◽  
Ballistic Impacts ◽  
Internal Lining ◽  
Maximum Protection ◽  
Fluid Solid Interaction ◽  
External Coating

Purpose – The purpose of this paper is to optimize the design of the advanced combat helmet (ACH) currently in use, by its designers in order to attain maximum protection against ballistic impacts (fragments, shrapnel, etc.) and hard-surface/head collisions. Since traumatic brain injury experienced by a significant fraction of the soldiers returning from the recent conflicts is associated with their exposure to blast, the ACH should be redesigned in order to provide the necessary level of protection against blast loads. In the present work, augmentations of the ACH for improved blast protections are considered. These augmentations include the use of a polyurea (a nano-segregated elastomeric copolymer)-based ACH external coating/internal lining. Design/methodology/approach – To demonstrate the efficacy of this approach, instrumented (unprotected, standard-ACH-protected, and augmented-ACH-protected) head-mannequin blast experiments are carried out. These experimental efforts are complemented with the appropriate combined Eulerian/Lagrangian transient non-linear dynamics computational fluid/solid interaction analysis. Findings – The results obtained indicated that: when the extent of peak over-pressure reduction is used as a measure of the blast-mitigation effectiveness, polyurea-based augmentations do not noticeably improve, and sometimes slightly worsen, the performance of the standard ACH; when the extent of specific impulse reduction is used as a measure of the blast-mitigation effectiveness, application of the polyurea external coating to the standard ACH improves the blast-mitigation effectiveness of the helmet, particularly at shorter values of the charge-detonation standoff distance (SOD). At longer SODs, the effects of the polyurea-based ACH augmentations on the blast-mitigation efficacy of the standard ACH are inconclusive; and the use of the standard ACH significantly lowers the accelerations experienced by the skull and the intracranial matter. As far as the polyurea-based augmentations are concerned, only the internal lining at shorter SODs appears to yield additional reductions in the head accelerations. Originality/value – To the authors’ knowledge, the present work contains the first report of a combined experimental/computational study addressing the problem of blast-mitigation by polyurea-based augmentation of ACH.

Experimental and computational investigations of the potential improvement in helmet blast-protection through the use of a polyurea-based external coating

2016 ◽  
Vol 12 (1) ◽  
pp. 33-72 ◽  
Author(s):  
M. Grujicic ◽  
S. Ramaswami ◽  
J. S. Snipes ◽  
R. Yavari ◽  
P. Dudt
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Computational Study ◽  
Element Analysis ◽  
Content Type ◽  
Ballistic Impacts ◽  
Blast Protection ◽  
Protection Efficacy ◽  
Potential Improvement ◽  
External Coating

Purpose – The design of the Advanced Combat Helmet (ACH) currently in use was optimized by its designers in order to attain maximum protection against ballistic impacts (fragments, shrapnel, etc.) and hard-surface/head collisions. Since traumatic brain injury experienced by a significant fraction of the soldiers returning from the recent conflicts is associated with their exposure to blast, the ACH should be redesigned in order to provide the necessary level of protection against blast loads. The paper aims to discuss this issue. Design/methodology/approach – In the present work, an augmentation of the ACH for improved blast protection is considered. This augmentation includes the use of a polyurea (a nano-segregated elastomeric copolymer) based ACH external coating. To demonstrate the efficacy of this approach, blast experiments are carried out on instrumented head-mannequins (without protection, protected using a standard ACH, and protected using an ACH augmented by a polyurea explosive-resistant coating (ERC)). These experimental efforts are complemented with the appropriate combined Eulerian/Lagrangian transient non-linear dynamics computational fluid/solid interaction finite-element analysis. Findings – The results obtained clearly demonstrated that the use of an ERC on an ACH affects (generally in a beneficial way) head-mannequin dynamic loading and kinematic response as quantified by the intracranial pressure, impulse, acceleration and jolt. Originality/value – To the authors’ knowledge, the present work is the first reported combined experimental/computational study of the blast-protection efficacy and the mild traumatic brain-injury mitigation potential of polyurea when used as an external coating on a helmet.

Creating the digital citizen: students’ co-construction of meaning for global citizenship during online discussions

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
John P. Myers
Keyword(s):  
Knowledge Construction ◽  
Meaning Making ◽  
Global Citizenship ◽  
Interaction Analysis ◽  
Discussion Board ◽  
Online Discussions ◽  
Discussion Boards ◽  
Discussion Forums ◽  
Analysis Model ◽  
Content Type

PurposeThis study examines whether online asynchronous discussion forums support student’s meaning-making about citizenship in a globalizing world. Citizenship is an increasingly contested identity for young people, yet they have few opportunities in traditional civic education to consider their own citizenship. Although online discussions are considered effective spaces for increasing dialogue and critical thinking between diverse students, there has been little research to understand how effective they are for helping students to construct new understandings of citizenship.Design/methodology/approachA content analysis approach was used to analyze and code 89 discussion board posts. The Interaction Analysis Model (IAM) coding scheme was used to describe and analyze the quality of knowledge construction that occurred across the posts focusing on different aspects of global citizenship.FindingsThe findings demonstrate that the discussion boards produced substantive talks about the meaning of citizenship that in some instances reached the level of new knowledge construction. The students considered different meanings for global citizenship and negotiated positions on key issues. However, the highest levels of knowledge construction were rarely reached.Practical implicationsA major implication is the need to organize and cue discussion boards to support knowledge construction in addition to fostering dialogue.Originality/valueThis study contributes to the role that technology can play in supporting students’ knowledge construction about global citizenship that go beyond the scripted meanings conveyed in civics classes.

Three-dimensional computational study in a corrugated pipe inserted system filled with phase change material

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ömer Akbal ◽  
Hakan F. Öztop ◽  
Nidal H. Abu-Hamdeh
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Computational Analysis ◽  
Computational Study ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Melting Time ◽  
Geometrical Parameters ◽  
Content Type ◽  
Change Material

Purpose The purpose of this paper is to make a three-dimensional computational analysis of melting in corrugated pipe inserted system filled with phase change material (PCM). The system was heated from the inner pipe, and temperature of the outer pipe was lower than that of inner pipe. Different geometrical ratio cases and two different temperature differences were tested for their effect on melting time. Design/methodology/approach A computational analysis through a pipe with corrugated pipe filled with PCM is analyzed. Finite volume method was applied with the SIMPLE algorithm method to solve the governing equations. Findings The results indicate that the geometrical parameters can be used to control the melting time inside the heat exchanger which, in turn, affect the energy efficiency. The fastest melting time is seen in Case 4 at the same temperature difference which is the major observation of the current work. Originality/value Originality of this work is to perform a three-dimensional analysis of melting of PCM in a corrugated pipe inserted pipe.

Promotion and shoppers' impulse purchases: the example of clothes

2014 ◽  
Vol 31 (2) ◽  
pp. 94-102 ◽  
Author(s):  
Peter Hultén ◽  
Vladimir Vanyushyn
Keyword(s):  
Specific Impulse ◽  
Product Category ◽  
Direct Mail ◽  
Seemingly Unrelated Regression ◽  
Interactive Effects ◽  
Impulse Buying ◽  
Content Type ◽  
Impulse Purchases ◽  
Tv Commercials ◽  
Buying Behaviour

Purpose – This paper draws attention to the fact that impulse buying is common behaviour among modern shoppers and that a consumer's impulse purchases of items such as clothes may be a result of the retailers' promotional activities. The purpose of this paper is therefore to investigate how promotion through channels such as direct-mail marketing, TV commercials and special in-store displays affects consumers' impulse purchases of clothes. Design/methodology/approach – Data for the testing of five hypotheses was collected by distributing a questionnaire to randomly selected households in North Western France and Northern Sweden. The data collection rendered 493 complete questionnaires, of which 332 were from France and 161 from Sweden. Seemingly unrelated regression (SUR) is the principal estimation technique. Findings – The results suggest that shoppers with a positive attitude towards direct-mail marketing and TV commercials also respond positively to in-store promotion. Hence, there are interactive effects between the three promotional channels that increase shoppers' general impulse purchase tendency. Furthermore, the findings demonstrate that the frequency of exposure to in-store promotion has a significant effect on this tendency. Originality/value – This paper contributes to extant knowledge on impulse buying behaviour by examining the product-specific impulse tendency, which is defined as the degree to which consumers make impulse purchases of a particular product category.

Evaluation of bend curvature of superheater tube using CFD analysis

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sushovan Chatterjee ◽  
Subhasish Das ◽  
Neelam Kumar Sarma
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Flow Behavior ◽  
Radius Of Curvature ◽  
Pass System ◽  
Maximum Heat ◽  
Curvature Ratio ◽  
Content Type ◽  
Superheater Tube ◽  
The Impact

Purpose The heat transfer within a heat exchanger is highly influenced by geometry of the components especially those with hollow structures like tubes. This paper aims to intend toward the study of efficient and optimized heat transfer in the bends of superheater tubes, with different curvature ratio at constant Reynolds Number. Design/methodology/approach The effect of changing curvature ratio on enthalpy of the fluid passing through the superheater tubes for multi-pass system has been studied with the aid of computational fluid dynamics (CFD) using ANSYS 14.0. Initially a superheater tube with two pass system has been examined with different curvature ratios of 1.425, 1.56, 1.71, 1.85 and 1.99. An industry specified curvature ratio of 1.71 with two pass is investigated, and a comparative assessment has been carried out. This is intended toward obtaining an optimized radius of curvature of the bend for enhancement of heat transfer. Findings The results obtained from software simulation revealed that the curvature ratio of 1.85 provides maximum heat transfer to the fluid flowing through the tube with two pass. This result has been found to be consistent with higher number of passes as well. The effect of secondary flow in bends of curvature has also been illustrated in the present work. Research limitations/implications The study of heat transfer in thermodynamic systems is a never-ending process and has to be continued for the upliftment of power plant performances. This study has been conducted on steady flow behavior of the fluid which may be upgraded by carrying out the same in transient mode. The impact of different curvature ratios on some important parameters such as heat transfer coefficients will certainly upgrade the value of research. Originality/value This computational study provided comprehensive information on fluid flow behavior and its effect on heat transfer in bends of curvature of superheater tubes inside the boiler. It also provides information on optimized bend of curvature for efficient heat transfer process.

scholarly journals Decyl Gallate as a Possible Inhibitor of N-Glycosylation Process in Paracoccidioides lutzii

2019 ◽  
Vol 63 (11) ◽  
Author(s):  
Ana Carolina Alves de Paula e Silva ◽  
Haroldo Cesar de Oliveira ◽  
Liliana Scorzoni ◽  
Caroline Maria Marcos ◽  
Claudia Tavares dos Santos ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Fluorescent Protein ◽  
Genetic Interaction ◽  
Interaction Analysis ◽  
Biological Activities ◽  
Lung Epithelial Cells ◽  
Mitochondrial Activity ◽  
Content Type ◽  
Unfolded Protein ◽  
Protein Response

ABSTRACT The available antifungal therapeutic arsenal is limited. The search for alternative drugs with fewer side effects and new targets remains a major challenge. Decyl gallate (G14) is a derivative of gallic acid with a range of biological activities and broad-spectrum antifungal activity. Previously, our group demonstrated the promising anti-Paracoccidioides activity of G14. In this work, to evaluate the antifungal characteristics of G14 for Paracoccidioides lutzii, a chemical-genetic interaction analysis was conducted on a Saccharomyces cerevisiae model. N-glycosylation and/or the unfolded protein response pathway was identified as a high-confidence process for drug target prediction. The overactivation of unfolded protein response (UPR) signaling was confirmed using this model with IRE1/ATF6/PERK genes tagged with green fluorescent protein (GFP). In P. lutzii, this prediction was confirmed by the low activity of glycosylated enzymes [α-(1,3)-glucanase, N-acetyl-β-d-glucosaminidase (NAGase), and α-(1,4)-amylase], by hyperexpression of genes involved with the UPR and glycosylated enzymes, and by the reduction in the amounts of glycosylated proteins and chitin. All of these components are involved in fungal cell wall integrity and are dependent on the N-glycosylation process. This loss of integrity was confirmed by the reduction in mitochondrial activity, impaired budding, enhancement of wall permeability, and a decrease in viability. These events led to a reduction of the ability of fungi to adhere on human lung epithelial cells (A549) in vitro. Therefore, G14 may have an important role in balancing the inflammatory reaction caused by fungal infection, without interfering with the microbicidal activity of nitric oxide. This work provides new information on the activity of G14, a potential anti-Paracoccidioides compound.

scholarly journals Steroid Hydroxylation by Basidiomycete Peroxygenases: a Combined Experimental and Computational Study

2015 ◽  
Vol 81 (12) ◽  
pp. 4130-4142 ◽  
Author(s):  
Esteban D. Babot ◽  
José C. del Río ◽  
Marina Cañellas ◽  
Ferran Sancho ◽  
Fátima Lucas ◽  
...  
Keyword(s):  
Computational Study ◽  
Biological Activities ◽  
Side Chain ◽  
Enzymatic Reactions ◽  
Fungal Enzymes ◽  
Content Type ◽  
Protein Energy ◽  
Esterified Sterols ◽  
Ligand Diffusion ◽  
Protein Energy Landscape

ABSTRACTThe goal of this study is the selective oxyfunctionalization of steroids under mild and environmentally friendly conditions using fungal enzymes. With this purpose, peroxygenases from three basidiomycete species were tested for the hydroxylation of a variety of steroidal compounds, using H2O2as the only cosubstrate. Two of them are wild-type enzymes fromAgrocybe aegeritaandMarasmius rotula, and the third one is a recombinant enzyme fromCoprinopsis cinerea. The enzymatic reactions on free and esterified sterols, steroid hydrocarbons, and ketones were monitored by gas chromatography, and the products were identified by mass spectrometry. Hydroxylation at the side chain over the steroidal rings was preferred, with the 25-hydroxyderivatives predominating. Interestingly, antiviral and other biological activities of 25-hydroxycholesterol have been reported recently (M. Blanc et al., Immunity 38:106–118, 2013,http://dx.doi.org/10.1016/j.immuni.2012.11.004). However, hydroxylation in the ring moiety and terminal hydroxylation at the side chain also was observed in some steroids, the former favored by the absence of oxygenated groups at C-3 and by the presence of conjugated double bonds in the rings. To understand the yield and selectivity differences between the different steroids, a computational study was performed using Protein Energy Landscape Exploration (PELE) software for dynamic ligand diffusion. These simulations showed that the active-site geometry and hydrophobicity favors the entrance of the steroid side chain, while the entrance of the ring is energetically penalized. Also, a direct correlation between the conversion rate and the side chain entrance ratio could be established that explains the various reaction yields observed.

Computational Study on Influence of Water Injection Angle to Aluminum/Water Reaction Motor

2012 ◽  
Vol 248 ◽  
pp. 539-544
Author(s):  
Zheng He ◽  
Xuan Gu ◽  
Ye Gao
Keyword(s):  
Computational Study ◽  
Aluminum Particle ◽  
Specific Impulse ◽  
Water Injection ◽  
Water Droplets ◽  
Aluminum Particles ◽  
Injection Angle ◽  
Influence Of Water ◽  
Afterburning Chamber ◽  
Multi Phase

In Aluminum/Water Reaction Motor chamber, water injection angle plays an important role on mixture of aluminum particle fuel and water droplets and can affect motor performance further. On the basis of FLUENT software and taking phase transition and reaction between water droplets and aluminum particles into account, numerically simulated cases of different water injection angles by Particle Stochastic Trajectory Model. Computed total evaporation rate of water droplets, reaction rate of aluminum particles and specific impulse for the motor. Furthermore judged injection angle effect from these parameters. By comparison and analysis, it is found that hybrid injection case could get best multi-phase mixture effect and specific impulse performance for the motor. Namely axial injection angle with 45°in the main chamber and tangential injection angle with 60°in the afterburning chamber is the best case. The conclusion could provide a new idea for motor working process design.

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