scholarly journals Alumina-Based Ceramics for Armor Application: Mechanical Characterization and Ballistic Testing

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
M. V. Silva ◽  
D. Stainer ◽  
H. A. Al-Qureshi ◽  
O. R. K. Montedo ◽  
D. Hotza
Keyword(s):  
Standard Deviation ◽  
Kinetic Energy ◽  
Mechanical Characterization ◽  
Industrial Plant ◽  
Metallic Plate ◽  
Thick Plates ◽  
Lower Standard ◽  
Aisi 1045 ◽  
Ballistic Test ◽  
Ballistic Testing

The aim of this work is to present results of mechanical characterization and ballistic test of alumina-based armor plates. Three compositions (92, 96, and 99 wt% Al2O3) were tested for 10 mm thick plates processed in an industrial plant. Samples were pressed at 110 MPa and sintered at 1600°C for 6 h. Relative density, Vickers hardness, and four-point flexural strength measurements of samples after sintering were performed. Results showed that the strength values ranged from 210 to 300 MPa depending on the porosity, with lower standard deviation for the 92 wt% Al2O3 sample. Plates (120 mm × 120 mm × 12 mm) of this composition were selected for ballistic testing according to AISI 1045, using a metallic plate as backing and witness plates in the case of penetration or deformation. Standard NIJ-0108.01 was followed in regard to the type of projectile to be used (7.62 × 51 AP, Level IV, 4068 J). Five alumina plates were used in the ballistic tests (one shot per plate). None of the five shots penetrated or even deformed the metal sheet, showing that the composition containing 92 wt% Al2O3 could be considered to be a potential ballistic ceramic, being able to withstand impacts with more than 4000 J of kinetic energy.

scholarly journals Linear and Angular Deviations of Implants Placed in Experimental Casts with Stereolithographic Drill Guides Fixed by O'ring Ortho Implant Devices

2013 ◽  
Vol 24 (4) ◽  
pp. 391-396 ◽  
Author(s):  
Marcelo Michele Novellino ◽  
Newton Sesma ◽  
Dalva Cruz Lagana ◽  
Glais Ferrari
Keyword(s):  
Standard Deviation ◽  
Bone Tissue ◽  
Test Group ◽  
Control Group ◽  
Implant Surgery ◽  
Lower Standard Deviation ◽  
Surgical Template ◽  
Lower Standard ◽  
Cad Cam ◽  
Surgical Templates

The aim of this study was to evaluate whether the introduction of a device, resulting from the combination of an o'ring attachment with an orthodontic implant (o'ring ortho implant, O'ROI), to affix the surgical template of CAD/CAM-guided implant surgery contribute to minimizing the deviations in the position and inclination of implants at the time of their placement. Ten models simulating bone tissue were fabricated and randomly divided into 2 groups: 5 with the scanning and surgical template of the usual technique, representing the Control Group (C), and 5 with scanning and surgical templates fixed by o'ring ortho implants (O'ROI), representing the Test Group (T). Forty implants measuring 4×11 mm were placed in the groups, using the respective templates. The results were evaluated by the fusion of CT images of the planned and placed implants. The locations and axes were compared. There were no statistically significant differences for the angular (Tukey's test F = 1.06 and p = 0. 3124) and linear (ANOVA F = 2.54 and p = 0.11) deviations. However, the angular values of Group T showed a lower standard deviation in comparison with those of Group C. The use of o'ring ortho implants (O'ROI) is able to minimize the angular and linear deviation of implants at the time of their placement.

scholarly journals Kinematics and dynamics of the ballistic impact behavior for an oil palm empty fruit bunch fiber reinforced bio-composite

BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 6123-6134
Author(s):  
Siti Nikmatin ◽  
Bambang Hermawan ◽  
Irmansyah ◽  
Mohammad Nur Indro ◽  
Mochammad Danny Sukardan ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Ballistic Impact ◽  
Impact Behavior ◽  
Kinematics And Dynamics ◽  
Empty Fruit Bunch ◽  
Fiber Reinforced ◽  
Polyester Resins ◽  
Ballistic Test ◽  
The Impact ◽  
Main Material

The ballistic impact behavior of oil empty fruit bunch fiber reinforced bio-composites was studied. Epoxy and polyester resins were used as the main material and were evaluated as a matrix to determine their capability. The ballistic test was performed using a 9 mm handgun and a jacketed hollow point round. A model based on kinematics and dynamics was used to calculate the decrease in velocity of the projectile with a constant deceleration. The energy lost during the impact was calculated based on the theory of kinetic energy. The epoxy bio-composite was able to hold a projectile more successfully than the polyester bio-composite at a certain penetration depth. The curve of the decrease in velocity for both of the resins was exponentially distributed. An 18% epoxy bio-composite was able to more successfully stop the projectile at a penetrative depth of 2.14 mm and was able to absorb all the kinetic energy generated (408 J).

Fine-Tuning Geometrically Constrained Planar Motions

2011 ◽  
Author(s):  
Ping Zhao ◽  
Q. J. Ge ◽  
Feng Gao ◽  
Hai-Jun Su
Keyword(s):  
Standard Deviation ◽  
Kinetic Energy ◽  
Reference Frames ◽  
Distance Measure ◽  
Fine Tuning ◽  
Planar Motion ◽  
Motion Error ◽  
Point Trajectories ◽  
Geometrically Constrained ◽  
Planar Motions

This paper presents a method for fine-tuning a geometrically constrained planar motion in the context of motion approximation. It builds on the recent work that seeks to identify and extract point trajectories of an explicitly given planar motion. Once two point trajectories are obtained, the remaining issue is to determine the length of the “coupler link” that connects the two point trajectories such that the resulting motion best approximates the original motion. In this paper, the concept of standard deviation in statistics and probability theory is used to define the “distance” between two planar motions. This distance definition is bi-invariant with respect to the choice of both moving and fixed reference frames. Furthermore, the concept of kinetic energy is also used for combining translation with rotation when calculating the distance between two planar displacements. A simple, direct search method for obtaining the optimum length of the coupler link is presented that minimizes the standard deviation of the motion error in terms of the kinetic energy based distance measure for planar displacements.

On the modified Circumpolar Deep Water upwelling over the Four Ladies Bank in Prydz Bay, East Antarctica

2020 ◽  
Author(s):  
Chengyan Liu ◽  
Zhaomin Wang ◽  
Chen Cheng ◽  
Xi Liang ◽  
Yang Wu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Standard Deviation ◽  
Kinetic Energy ◽  
Potential Temperature ◽  
Weddell Sea ◽  
East Antarctica ◽  
Prydz Bay ◽  
Ice Shelf ◽  
Borehole Data ◽  
Amery Ice Shelf

<p>We report on mooring observations of tidal currents in Prydz Bay, East Antarctica. Tides in Prydz Bay are mixed diurnal-semidiurnal and much weaker than that in the Ross Sea and the Weddell Sea, with the spatial and temporal averaged value of 2.58 cm s<sup>-1</sup> for all the current meter observations over the continental shelf. The major axes of the tidal ellipses are generally aligned south-north, probably steered by the topography. The tidal phases are modulated by both the baroclinic and barotropic tidal components. The averaged tidal kinetic energy can account for a fraction of ~13% with respect to the total kinetic energy at the Amery Ice Shelf calving front during the observing period. The long-term average tidal heat flux across the Amery Ice Shelf calving front is negligible, but the ratio of the tidal heat flux standard deviation to the residual heat flux standard deviation can be up to 41%. We also report on borehole observations of tide-like pulsing of potential temperature and salinity, indicating the indispensable tidal influences in the ice-ocean boundary layer. These mooring and borehole data support that the tidal processes should be highlighted in the investigations of the interaction between the Amery Ice Shelf and ocean.</p>

scholarly journals Influencia de la emisión de neutrones en la medición por el método de la doble energía de la distribución de masa y energía cinética de los fragmentos de la fisión espontánea del 252Cf

2019 ◽  
pp. 15-19
Keyword(s):  
Monte Carlo ◽  
Standard Deviation ◽  
Monte Carlo Method ◽  
Kinetic Energy ◽  
Energy Distribution ◽  
Energy Method ◽  
Spontaneous Fission ◽  
Neutron Emission ◽  
Mass Energy ◽  
San Marcos

Influencia de la emisión de neutrones en la medición por el método de la doble energía de la distribución de masa y energía cinética de los fragmentos de la fisión espontánea del 252Cf Influence of neutron emission on the measurement by double-energy method of mass and kinetic energy distribution of the fragments from spontaneous fission of 252Cf Modesto Montoya, Carlos Romero y Justo Rojas Instituto Peruano de Energía Nuclear Universidad Nacional de Ingeniería, Av. Túpac Amaru 210, Rímac, Lima Universidad Nacional Mayor de San Marcos, Av. Venezuela, s/n, Callao DOI: https://doi.org/10.33017/RevECIPeru2011.0003/ RESUMEN El método de doble energía ha sido usado por varios autores para medir la distribución de masa (A*) y energía cinética total de los fragmentos complementarios (EKT*) de la fisión espontánea del 252Cf, encontrándose un ensanchamiento de la desviación estándar de distribución de EKT* (σEKT*) en la región cercana a la simetría de masas (A* = 226). Usando el método Monte Carlo, nosotros mostramos que ese ensanchamiento se debe que para cada valor de A* se produce la superposición de distribuciones de EKT* correspondientes a fragmentos primarios con dos o más masas vecinas, respectivamente. Descriptores: fision espontánea, 252Cf, fragmentos distribución masa energía. ABSTRACT The double energy method has been used by several authors to measure the mass (A *) and total kinetic energy (EKT *) distribution of the complementary fragments from spontaneous fission of 252Cf, finding an broadening of the distribution standard deviation EKT * (σEKT *) in the region near mass symmetry (A * = 226). Using Monte Carlo method, we show that this broadening is because for each value of A * an overlapping of distributions EKT * for primary fragments with two or more neighboring masses, respectively, are produced. Keywords: spontaneous fission 252Cf, fragments distribution mass energy.

scholarly journals Diurnal cycle of short-term fluctuations of integrated water vapour above Switzerland

2019 ◽  
Author(s):  
Klemens Hocke ◽  
Leonie Bernet ◽  
Jonas Hagen ◽  
Axel Murk ◽  
Matthias Renker ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Kinetic Energy ◽  
Water Vapour ◽  
Diurnal Cycle ◽  
Time Window ◽  
Convective Heating ◽  
Short Term ◽  
Filtering Method ◽  
Integrated Water Vapour ◽  
Band Pass

Abstract. The TROpospheric WAter RAdiometer (TROWARA) continuously measures integrated water vapour (IWV) with a time resolution of 6 seconds at Bern in Switzerland. During summer, we often see that IWV has temporal fluctuations during daytime while the night-time data are without fluctuations. The data analysis is focused on the year 2010 where TROWARA has a good data quality without data gaps. We derive the spectrum of the IWV fluctuations in the period range from about 1 to 100 min. The FFT spectrum with a window size of 3 months leads to a serious underestimation of the spectral amplitudes of the fluctuations. Thus, we apply a band pass filtering method to derive the amplitudes as a function of period Tp. The amplitudes are proportional to Tp0.5. Another method is the computation of the moving standard deviation with time window lengths from about 1 to 100 min. Here, we get similar results as for the band pass filtering method. At all periods, the IWV fluctuations are strongest during summer while they are smallest during winter. We derive the diurnal variation of the short-term IWV fluctuations by applying a moving standard deviation with a window length of 10 min. The daily cycle is strongest during the summer season with standard deviations up to 0.22 mm at about 14:00 CET. The diurnal cycle disappears during winter time. Using the meteorological weather station at Bern, we derive the diurnal cycle of the short-term fluctuations of the specific kinetic energy ek. Since these data have a temporal resolution of 10 min, we apply a 20 min-moving standard deviation. The derived short-term ek fluctuations can be regarded as a proxy of turbulent kinetic energy (TKE). During summer time, the 20 min-moving standard deviation of ek increases during daytime and has a similar diurnal cycle like the short-term IWV fluctuations. Thus, we conclude that the diurnal cycle of the short-term IWV fluctuations is caused by turbulence associated with large convective heating during daytime in summer.

scholarly journals Numerical hull resistance calculation of a catamarán using OpenFOAM

2017 ◽  
Vol 11 (21) ◽  
pp. 29
Author(s):  
Diana S. Hurtado Bustos ◽  
Rubén J. Paredes Alvarado
Keyword(s):  
Experimental Data ◽  
Standard Deviation ◽  
Numerical Simulations ◽  
Light Condition ◽  
Lower Standard Deviation ◽  
Lower Standard ◽  
Convergence Study ◽  
Travel Services ◽  
Mesh Convergence ◽  
Load Conditions

In the present study, numerical resistance predictions using OpenFOAM were performed considering the Cormorant Evolution Catamaran, which provides travel services in the Galapagos Islands. These predictions were compared with experimental data published by Chávez and Lucín [1] and with systematic series [2].Simulations were made at model scale of 2 [m] in two load conditions, considering demi and twin hull (s=0.56 [m]) configurations. A mesh convergence study was performed with 3 different meshes for V=1.05 [m/s] at Light Condition (T=0.086 [m]). The converged mesh, with 1 million of cells approximately, has the lower standard deviation and a 5% error when compared to its experimental value of 1.79 [N]. The errors between the experimental data and the numerical simulations for demi hull configuration were 43% and 36% for Light and Full conditions, respectively. Besides, for twin hull configuration the errors were around 14% and 32% for Light and Full conditions, respectively.

scholarly journals Does Value Averaging Strategy Improve Investment Performance? Evidence from the Korean Fund Market

2020 ◽  
Vol 49 (3) ◽  
pp. 313-340
Author(s):  
Hyuk Choe ◽  
Ju Il Ban
Keyword(s):  
Standard Deviation ◽  
Performance Analysis ◽  
Asset Allocation ◽  
Expected Return ◽  
Investment Performance ◽  
Average Return ◽  
A Value ◽  
Ex Ante ◽  
Lower Standard ◽  
Two Alternatives

This study analyzes whether a value averaging (VA) strategy, which adjusts the amount of investment each period to achieve the target amount of investment in risk assets, as a modified form of a dollar cost averaging (DCA) strategy, improves investment performance. Using 18.5 years of fund market data in Korea from 2001 to June 2019, we compare the investment performance of VA strategy relative to two alternatives: DCA strategy, which invests a certain amount in each period, and Buy-and-Hold (BH) strategy, which refers to half-and-half asset allocation between risky and risk-free assets and has an expected return which is the same as that of DCA in the ex-ante sense. Our historical performance analysis reveals that the VA strategy has lower average return and higher standard deviation compared to the BH strategy and has lower average return and lower standard deviation compared to the DCA strategy. These findings are in stark contrast to the claims made by advocates of VA strategy that the strategy improves investment performance.

Audit Fees and Client Industry Homogeneity

2015 ◽  
Vol 34 (4) ◽  
pp. 33-57 ◽  
Author(s):  
Timothy D. Cairney ◽  
Errol G. Stewart
Keyword(s):  
Standard Deviation ◽  
Audit Fees ◽  
Data Availability ◽  
Negatively Associated ◽  
Lower Standard Deviation ◽  
Lower Standard ◽  
The Relationship ◽  
Industry Homogeneity

SUMMARY This study examines the relationship between a client industry's homogeneity and audit fees. We assume that audit efficiencies occur in audits in industries whose members have similar operations and, therefore, are where auditors benefit from the use of similar audit procedures and experience lower average audit costs. To identify industries with similar operations, we use operational expense homogeneity, which is based on the correlations between the changes in operating expenses among industry members. Adapting a standard fee model (Hay, Knechel, and Wong 2006), we find that homogeneity is negatively associated with audit fees. Further, we find that specialist auditors charge lower fees in homogenous industries. Finally, we observe a lower standard deviation of fees in more homogenous industries. Together, these results suggest that auditors sustain lower costs in audits of homogenous clients and that the similarly lower costs incurred across auditors are passed on to clients in the form of lower fees. Data Availability: Data used in this paper are available from the sources listed in the paper.

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