scholarly journals Improving the Blast Resistance of Large Steel Gates—Numerical Study

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2121 ◽  
Author(s):  
Hasan Al-Rifaie ◽  
Wojciech Sumelka
Keyword(s):  
Positive Impact ◽  
Numerical Study ◽  
Blast Resistance ◽  
Critical Factor ◽  
Induced Response ◽  
Dissipation Energy ◽  
Auxetic Structures ◽  
Explicit Solver ◽  
Supporting Frame ◽  
Energy Absorbing

Blast resistant gates/doors are essential for sensitive infrastructure, such as embassies, ministries, or parliaments. Lightweight gates equipped with ‘energy absorbing systems’ have better operational performance than the traditional costly and bulky design. Graded auxetic structures have not yet been used as potential passive damping systems in the supporting frame of blast resistant gates. Consequently, this study tries to test if a uniaxial graded auxetic damper (UGAD) proposed by the authors in a recent article, namely the development of a new shock absorbing UGAD, could maintain a 3000 mm × 4500 mm steel gate operable after high blast peak reflected overpressure of 6.6 MPa, from 100 kg TNT at 5 m stand-off distance. The blast-induced response of the gate was assessed, with and without the proposed UGAD, using Abaqus/Explicit solver. Results showed that the attachment of the proposed UGAD to the gate led to a dramatic decrease in permanent deformations (a critical factor for gate operability after a blast event). Hence, a lighter, more economical gate (with 50% reduction in mass) was required to satisfy the operability condition. In addition, 49% of peak reaction forces were diminished, that have a direct impact on the supporting frame. Moreover, the results revealed that, in the numerical model, 56% of the achieved plastic dissipation energy was from the UGADs, and 44% from the gate. The outcomes of this research may have a positive impact on other sectors beyond academia, such as industry, economy, and public safety.

Numerical Study on Explosion Cutting Process of PMMA Plate and Key Factors Influence on Cutting Performance

2018 ◽  
Author(s):  
Lei Ge ◽  
Yantao Wang ◽  
Huipeng Hu ◽  
Lijun Li ◽  
Yiben Zhang
Keyword(s):  
Numerical Study ◽  
Engineering Application ◽  
Material Model ◽  
Cutting Performance ◽  
Cutting Process ◽  
Transient Pressure ◽  
Key Factors ◽  
Explicit Solver ◽  
The Relationship ◽  
Selection Of

Polymethylmethacrylate (PMMA) has been widely utilized to manufacture the covers of aircraft cockpits, naval vessels, car windows and so on, due to their high transmittance, low density, easy processing formability, high corrosion resistance and excellent mechanical properties. Under special conditions such as ejection lifesaving, the PMMA plate needs to be split precisely by explosion cutting technology. Hence, an accurate numerical simulation of PMMA structures is significantly important in engineering application. This paper aims to study the cutting behavior of PMMA plate numerically and investigate the influencing factors on cutting performance of PMMA plates. First of all, the simulation of explosion cutting process of PMMA plate is carried out by a non-linear explicit solver in LS-DYNA software using the fluid-solid coupling method. Jones-Wilkins-Lee (JWL) equation of state is used to simulate the relationship between the transient pressure and specific volume of explosives during explosion. The material model considering failure behaviors is used in the simulation. Additionally, the influence of explosive dosage as well as explosive type on the cutting performance of PMMA plate is investigated. Furthermore, the effect of PMMA geometry size on cutting performance is discussed. This study contributes to the knowledge for the design of PMMA structures which needs explosion cutting and the selection of explosive dosage and explosive type.

Systematic Literature Review:Online Social Media Interaction in Education and Employment Cluster/ Tinjauan Literatur Sistematik: Interaksi Media Sosial Atas Talian dalam Kluster Pendidikan dan Pekerjaan

2020 ◽  
Vol 12 (3) ◽  
Author(s):  
Nor Shela Saleh ◽  
Mohd Shafie Rosli
Keyword(s):  
Social Media ◽  
Factor Analysis ◽  
Positive Impact ◽  
Critical Factor ◽  
Online Interaction ◽  
Online Social Media ◽  
Employment Sector ◽  
The Face ◽  
Media Interaction ◽  
Education And Employment

The research is related to online social media interactions in education and employment clusters. The researcher has developed five objectives of the study specifically to identifying the top forms of social media in Malaysia, to identifying the tendency of Malaysians to habit social media, to identifying online interaction platforms in the employment sector, to identifying the effectiveness of social media in generating income and for educational purposes. All objectives use two methods of analysis that is critical factor analysis and quantitative analysis. All of these objectives were achieved. The results show that Malaysians are more likely to use Facebook social media and WhatsApp application in their regular lives for social, educational and career purposes. This shows that social media and interaction applications have a positive impact on society, especially for employees and students in the face of the changing world of Technology in the 21st century.

scholarly journals Dynamic Compressive Behaviors of Two-Layer Graded Aluminum Foams under Blast Loading

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1445 ◽  
Author(s):  
Minzu Liang ◽  
Xiangyu Li ◽  
Yuliang Lin ◽  
Kefan Zhang ◽  
Fangyun Lu
Keyword(s):  
Energy Absorption ◽  
Aluminum Foam ◽  
Blast Resistance ◽  
Blast Loading ◽  
Deformation Energy ◽  
Aluminum Foams ◽  
Conflicting Objectives ◽  
Energy Dissipated ◽  
Transmitted Impulse ◽  
Energy Absorbing

Experimental and numerical analyses were carried out to reveal the behaviors of two-layer graded aluminum foam materials for their dynamic compaction under blast loading. Blast experiments were conducted to investigate the deformation and densification wave formation of two-layer graded foams with positive and negative gradients. The shape of the stress waveform changed during the propagation process, and the time of edge rising was extended. Finite element models of two-layer graded aluminum foam were developed using the periodic Voronoi technique. Numerical analysis was performed to simulate deformation, energy absorption, and transmitted impulse of the two-layer graded aluminum foams by the software ABAQUS/Explicit. The deformation patterns were presented to provide insights into the influences of the foam gradient on compaction wave mechanisms. Results showed that the densification wave occurred at the blast end and then gradually propagated to the distal end for the positive gradient; however, compaction waves simultaneously formed in both layers and propagated to the distal end in the same direction for the negative gradient. The energy absorption and impulse transfer were examined to capture the effect of the blast pressure and the material gradient. The greater the foam gradient, the more energy dissipated and the more impulse transmitted. The absorbed energy and transferred impulse are conflicting objectives for the blast resistance capability of aluminum foam materials with different gradient distributions. The results could help in understanding the performance and mechanisms of two-layer graded aluminum foam materials under blast loading and provide a guideline for effective design of energy-absorbing materials and structures.

scholarly journals Effectiveness of birthing kits for clean childbirth: a systematic review

2019 ◽  
Vol 12 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Zohra S Lassi ◽  
Zeshi Fisher ◽  
Prabha Andraweera ◽  
Alexandra Cummins ◽  
Claire T Roberts
Keyword(s):  
Large Scale ◽  
Positive Impact ◽  
Young Infant ◽  
Critical Factor ◽  
Neonatal Morbidity ◽  
Qualitative Studies ◽  
Current Evidence ◽  
Cochrane Library ◽  
Quantitative Studies ◽  
Life Threatening

Abstract Poor infection control practices during childbirth are recognised as a critical factor leading to life-threatening maternal and newborn sepsis. Therefore, this paper assesses the effectiveness of clean birth kits (CBKs) to ensure a safe birthing environment. We searched PubMed, Cochrane Library and CINAHL, as well as Google Scholar, to identify both qualitative and quantitative studies on CBKs published in English up to November 2018. Studies were included if the pregnant women or women giving birth intended to use or used a CBK. The methodological quality of included papers was assessed. A total of 37 studies, 26 quantitative and 11 qualitative studies, were included. Quantitative studies showed a positive impact of CBKs on reducing the incidence of puerperal sepsis and neonatal tetanus. The review also identified CBK use to be associated with a reduction in perinatal, neonatal and young infant mortality. Qualitative studies suggested that a lack of awareness of the importance of CBKs and clean delivery practices, unavailability of CBKs and financial constraints to purchase CBKs were the potential barriers. CBKs appear to be a promising strategy to reduce maternal and neonatal morbidity and mortality. However, the current evidence is limited and further large-scale trials are required.

Numerical Study of Pressure Wave Transmission in Liquid Under Different Interface Conditions Using Particle Method

2009 ◽  
Author(s):  
Zhongguo Sun ◽  
Guang Xi
Keyword(s):  
Free Surface ◽  
Pressure Wave ◽  
Numerical Study ◽  
Wave Length ◽  
Particle Method ◽  
Wave Transmission ◽  
Wave Transport ◽  
Moving Particle ◽  
Energy Absorbing ◽  
The Waves

The process of pressure wave transmission in liquid is simulated with the moving particle semi-implicit (MPS) method. The simulation is carried out in a tube full filled with an energy absorbing liquid. Here we studied the shapes and positions of pressure waves and investigated the behavior of the waves under different viscosities and densities of liquids. Some typical parameters of pressure wave, such as peak pressure value, wave length and transport speed are studied. Varying viscosity does not change the wave length and speed of the pressure wave evidently. The effect of interfaces which formed by viscosity difference or density difference is investigated. Reflection is found not always happened on such interfaces. Pressure wave transport to liquid-solid interface and free surface are also simulated. Pressure wave is vanished when closing to free surface. These results give useful qualitative suggestions on controlling the pressure wave in fluid engineering.

The Evolution of a Dispersant Spraying Platform from Turboprop to Jet Engine Aircraft

2017 ◽  
Vol 2017 (1) ◽  
pp. 2811-2825
Author(s):  
Claudia Caetano ◽  
Daniel White
Keyword(s):  
Oil Spill ◽  
Oil Spills ◽  
Response Times ◽  
Positive Impact ◽  
Weight Ratio ◽  
Critical Factor ◽  
Jet Engine ◽  
Preparation Phase ◽  
Oil Spill Response ◽  
Response Phase

ABSTRACT Abstract 2017-370. As a result of a successful modification to an Oil Spill Response Limited Boeing 727 aircraft (registration G-OSRA) to enable aerial dispersant spraying, a paper has been written, aiming to provide an insight into the introduction of a turbine aircraft dispersant-application platform and the implications of the evolution from turboprop to jet engine aircraft. Furthermore, Oil Spill Response Limited has recently commissioned and introduced a second aircraft of the same modification specification (registration G-OSRB). As a response technique, dispersant application can have a significant impact on tackling large quantities of oil at sea; however, much of its effectiveness relies on targeting the oil during the window of opportunity in which dispersant will work successfully, in the early stages of the weathering processes. Time is, therefore, a critical factor and it is this key aspect, as well as others explored in detail throughout the paper, that led to the development of a pioneering system, specifically designed to respond to oil spills, that will undoubtedly prove to have a positive impact in terms of response times to incident sites. The paper also presents the reasons supporting the choice of a Boeing 727-2S2F (RE) aircraft as the chosen platform for dispersant spraying operations, such as the power to weight ratio, cargo capacity, and rearward mounted engine positions, to name but a few. It is also important to analyse the benefits of the Boeing 727-2S2F (RE) and the dispersant spraying system it contains during the different stages of the incident life cycle, be it during the preparation phase or the response phase. In the preparation phase, one of the advantages to highlight is the resilience of having two aircraft operated under a back to back schedule of maintenance as envisioned by a maintenance program specially designed to ensure continuous operational availability. During the response phase, aircraft such as G-OSRA and G-OSRB benefit from reduced transit times to incident sites due to the higher speed through the air that is possible with jet aircraft. Also, the paper also compares some key performance indicators such as range and speed between the turboprop aircraft of choice, Hercules L-382 and the Boeing 727-2S2F (RE).

scholarly journals Examining the Links Leading to Behavioral Support for Change: An Expectancy Theory Perspective

2020 ◽  
pp. 1-08
Author(s):  
Farhan Mehboob ◽  
Noraini Othman
Keyword(s):  
Positive Impact ◽  
Academic Staff ◽  
Critical Factor ◽  
Behavioral Support ◽  
Cross Sectional ◽  
Staff Members ◽  
Implementing Change ◽  
The University ◽  
University Officials

Purpose of the study: An individual’s support for change is a critical factor in successfully and effectively implementing change. Therefore, identifying possible antecedents and mechanisms leading to one’s behavioral support for change is necessary. The study aims to unpack this avenue of research empirically by examining the role of both person and context as factors in promoting behavioral support for change. Methodology: Data was collected from 292 academic staff members of six public sector universities in Pakistan via cross-sectional means. A self-reported questionnaire was used to collect responses from the desired sample. SPSS 25 and AMOS were used to analyze the data for its relevance to the objectives of the study.  Main Findings: Results revealed a positive impact of change-efficacy on academic staff members’ behavioral support for change. Moreover, change-valence provides an effective intervening mechanism to translate the effect of change-efficacy on both dimensions of behavioral support for change, that is, compliance and championing behavior. Research limitations/implications: The study contributes to the existing literature on organizational change, particularly in the university setting, by examining and empirically validating the factors of both person and context as significant predictors of behavioral support for change among academic staff. However, more research is needed in other organizational and work contexts to further apply the study’s implications within these diverse contexts. Novelty/Originality of this study: The study offers useful insights for senior university officials intending to build support for change by enhancing academic staff levels of efficacy and positive expectations regarding such change and enables them to successfully execute the change-related tasks into viable actions.

scholarly journals Investigation of the topological charge stability for multi-ringed Laguerre–Gauss vortex beams to random distortions

2019 ◽  
Vol 43 (4) ◽  
pp. 567-576 ◽  
Author(s):  
M.S. Kirilenko ◽  
S.N. Khonina
Keyword(s):  
Positive Impact ◽  
Numerical Study ◽  
Complex Conjugate ◽  
Structural Redundancy ◽  
Vortex Phase ◽  
Information Preservation ◽  
Charge Stability ◽  
Vortex Beams ◽  
Random Fluctuations ◽  
Topological Charges

We performed a comparative numerical study of the conservation of properties of individual Laguerre-Gauss beams and their superpositions in a random environment. The simulation is based on the extended Huygens-Fresnel principle. Studies have shown that increasing the number of rings of Laguerre-Gauss modes with the same vortex order allows one to increase the ratio of the energy of the minimum informative coefficient to the energy of the maximum parasitic coefficient, which is important when detecting information encoded in the coefficients. In addition, an increase in the number of rings partially compensates for the stronger effect of random fluctuations on beams with high topological charges. Such a positive impact can be explained by the structural redundancy of multi-ring distributions (the vortex phase structure of the beam is repeated in each ring). A similar result was obtained for beams corresponding to a two-mode superposition. The best result on information preservation was obtained for the superposition with duplication of information in complex conjugate coefficients, and the best ratio of informative energy to parasitic one was obtained for beams with the largest area.

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