Inconsistency in 9 mm bullets : correlation of jacket thickness to post-impact geometry measured with non-destructive X-ray computed tomography

Fundamental to any ballistic armour standard is the reference projectile to be defeated. Typically, for certification purposes, a consistent and symmetrical bullet geometry is assumed, however variations in bullet jacket dimensions can have far reaching consequences. Traditionally, characteristics and internal dimensions have been analysed by physically sectioning bullets – an approach which is of restricted scope and which precludes subsequent ballistic assessment. The use of a non-destructive X-ray computed tomography (CT) method has been demonstrated and validated Kumar et al., 2011); the authors now apply this technique to correlate bullet impact response with jacket thickness variations. A set of 20 bullets (9 mm DM11) were selected for comparison and an image-based analysis method was employed to map jacket thickness and determine the centre of gravity of each specimen. Both intra- and inter-bullet variations were investigated, with thickness variations of the order of 200 um commonly found along the length of all bullets and angular variations of up to 50 um in some. The bullets were subsequently impacted against a rigid flat plate under controlled conditions (observed on a high-speed video camera) and the resulting deformed projectiles were re-analysed. The results of the experiments demonstrate a marked difference in ballistic performance between bullets from different manufacturers and an asymmetric thinning of the jacket is observed in regions of pre-impact weakness. The conclusions are relevant for future soft armour standards and provide important quantitative data for numerical model correlation and development. The implications of the findings of the work on the reliability and repeatability of the industry standard V50 ballistic test are also discussed

Finite-Element Modelling of Biotransistors

Current research efforts in biosensor design attempt to integrate biochemical assays with semiconductor substrates and microfluidic assemblies to realize fully integrated lab-on-chip devices. The DNA biotransistor (BioFET) is an example of such a device. The process of chemical modification of the FET and attachment of linker and probe molecules is a statistical process that can result in variations in the sensed signal between different BioFET cells in an array. In order to quantify these and other variations and assess their importance in the design, complete physical simulation of the device is necessary. Here, we perform a mean-field finite-element modelling of a short channel, two-dimensional BioFET device. We compare the results of this model with one-dimensional calculation results to show important differences, illustrating the importance of the molecular structure, placement and conformation of DNA in determining the output signal

Interfacial growth of HfOxNy gate dielectrics deposited using [(C2H5)2N]4Hf with O2 and NO

The interfacegrowth by oxygen diffusion has been investigated for 5 nm thick HfOxNy gate-quality dielectric films deposited on Si(100) by low-pressure pulsed metalorganic chemical vapor deposition.Analysis by x-ray photoelectron spectroscopy of the films deposited using the precursor tetrakis (diethylamido) hafnium with O2 showed that the films contained 4 at.\u200a% nitrogen. This increased to 11 at.\u200a% N when NO was used as the oxidant. Significant growth of the interface layer was observed for films exposed to air at ambient temperature and lower rates of growth were observed for vacuum annealedfilms and those with the higher N content. For filmsannealed in O2 at temperatures in the range 600\u2013900\u200a\ub0C, the activation energies of the interfacial growth were 0.36 and 0.25 eV for N concentrations of 11 and 4 at.\u200a%, respectively. The results were interpreted in terms of atomic oxygen formation in the bulk and reaction at the interface. The increase in N incorporation from 4 to 11 at.\u200a% increases the crystallization temperature from between 500 and 600\u200a\ub0C to between 600 and 700\u200a\ub0C.NRC publication: Ye

Ultrathin zirconium silicate films deposited on Si(100) using Zr(Oi-Pr)2(thd)2, Si(Ot-Bu)2(thd)2 and nitric oxide

Ultrathin Zr silicate films were deposited using Zr(Oi\uadPr)2(tetramethylheptanedione,thd)2, Si(Ot\uadBu)2(thd)2 and nitric oxide in a pulse-mode metallorganic chemical-vapor deposition apparatus with a liquid injection source. High resolution transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and medium energy ion scattering were employed to investigate the structure, surface roughness, chemical state, and composition of the films. The nitric oxide used as oxidizing gas, instead of O2, not only reduced the thickness of the interfacial layer but also removed the carbon contamination effectively from the bulk of the films. The as-deposited Zr silicate films with a Si:Zr ratio of 1.3:1 were amorphous, with an amorphous interfacial layer 0.3-0.6 nm thick. After a spike anneal in oxygen and a 60 s nitrogen anneal at 850\ub0C, these films remained amorphous throughout without phase separation, but the interfacial layer increased in thickness. No evidence of Zr\uadC and Zr\uadSi bonds were found in the films by XPS and carbon concentrations <0.1\u2009atom%, the detection limit, were obtained. The hysteresis, fixed charge density, and leakage current determined from capacitance-voltage analysis improved significantly after postdeposition anneals at 850\ub0C and the films exhibited promising characteristics for deep submicrometer metal-oxide-semiconductor devices.NRC publication: Ye

Thermal stability and diffusion in gadolinium silicate gate dielectric films

Gadolinium silicate films on Si(100) annealed in oxygen and vacuum at temperatures up to 800\u200a\ub0C were analyzed by Rutherford backscattering and narrow resonance nuclear profiling. Oxygen diffused into the film eliminating oxygen vacancies, but Si diffusion, previously observed in Al and Y oxides and in La and Zr silicate films, was absent. Higher-temperature annealing in oxygen resulted in the formation of an interfacial layer observable in high-resolution electron micrographs. Gd0.23Si0.14O0.63 films crystallize at temperatures between 1000 and 1050\u200a\ub0C. These observations combined with recent electrical measurements show that gadolinium silicate films may be a good candidate for the replacement of SiO2 in deep submicron metal\u2013oxide\u2013semiconductor gates.NRC publication: Ye

Crystallographic reconstruction study of the effects of finish rolling temperature on the variant selection during bainite transformation in C-Mn high-strength steels

The effect of finish rolling temperature (FRT) on the austenite- () to-bainite () phase transformation is quantitatively investigated in high-strength C-Mn steels. In particular, the present study aims to clarify the respective contributions of the conditioning during the hot rolling and the variant selection (VS) during the phase transformation to the inherited texture. To this end, an alternative crystallographic reconstruction procedure, which can be directly applied to experimental electron backscatter diffraction (EBSD) mappings, is developed by combining the best features of the existing models: the orientation relationship (OR) refinement, the local pixel-by-pixel analysis and the nuclei identification and spreading strategy. The applicability of this method is demonstrated on both quenching and partitioning (Q&P) and as-quenched lath-martensite steels. The results obtained on the C-Mn steels confirm that the sample finish rolled at the lowest temperature (829{\deg}C) exhibits the sharpest transformation texture. It is shown that this sharp texture is exclusively due to a strong VS from parent brass {110}, S {213} and Goss {110} grains, whereas the VS from the copper {112} grains is insensitive to the FRT. In addition, a statistical VS analysis proves that the habit planes of the selected variants do not systematically correspond to the predicted active slip planes using the Taylor model. In contrast, a correlation between the Bain group to which the selected variants belong and the FRT is clearly revealed, regardless of the parent orientation. These results are discussed in terms of polygranular accommodation mechanisms, especially in view of the observed development in the hot-rolled samples of high-angle grain boundaries with misorientation axes between and

Frequency drift in MR spectroscopy at 3T

Purpose: Heating of gradient coils and passive shim components is a common cause of instability in the B-0 field, especially when gradient intensive sequences are used. The aim of the study was to set a benchmark for typical drift encountered during MR spectroscopy (MRS) to assess the need for real-time field-frequency locking on MRI scanners by comparing field drift data from a large number of sites.Method: A standardized protocol was developed for 80 participating sites using 99 3T MR scanners from 3 major vendors. Phantom water signals were acquired before and after an EPI sequence. The protocol consisted of: minimal preparatory imaging; a short pre-fMRI PRESS; a ten-minute fMRI acquisition; and a long post-fMRI PRESS acquisition. Both pre- and post-fMRI PRESS were non-water suppressed. Real-time frequency stabilization/adjustment was switched off when appropriate. Sixty scanners repeated the protocol for a second dataset. In addition, a three-hour post-fMRI MRS acquisition was performed at one site to observe change of gradient temperature and drift rate. Spectral analysis was performed using MATLAB. Frequency drift in pre-fMRI PRESS data were compared with the first 5:20 minutes and the full 30:00 minutes of data after fMRI. Median (interquartile range) drifts were measured and showed in violin plot. Paired t-tests were performed to compare frequency drift pre- and post-fMRI. A simulated in vivo spectrum was generated using FID-A to visualize the effect of the observed frequency drifts. The simulated spectrum was convolved with the frequency trace for the most extreme cases. Impacts of frequency drifts on NAA and GABA were also simulated as a function of linear drift. Data from the repeated protocol were compared with the corresponding first dataset using Pearson's and intraclass correlation coefficients (ICC).Results: Of the data collected from 99 scanners, 4 were excluded due to various reasons. Thus, data from 95 scanners were ultimately analyzed. For the first 5:20 min (64 transients), median (interquartile range) drift was 0.44 (1.29) Hz before fMRI and 0.83 (1.29) Hz after. This increased to 3.15 (4.02) Hz for the full 30 min (360 transients) run. Average drift rates were 0.29 Hz/min before fMRI and 0.43 Hz/min after. Paired t-tests indicated that drift increased after fMRI, as expected (p &lt; 0.05). Simulated spectra convolved with the frequency drift showed that the intensity of the NAA singlet was reduced by up to 26%, 44 % and 18% for GE, Philips and Siemens scanners after fMRI, respectively. ICCs indicated good agreement between datasets acquired on separate days. The single site long acquisition showed drift rate was reduced to 0.03 Hz/min approximately three hours after fMRI.Discussion: This study analyzed frequency drift data from 95 3T MRI scanners. Median levels of drift were relatively low (5-min average under 1 Hz), but the most extreme cases suffered from higher levels of drift. The extent of drift varied across scanners which both linear and nonlinear drifts were observed.</p

The effect of bullet yaw on the threat level : a numerical investigation

It is well known that yaw can affect the penetrative power of armour piercing rounds. To investigate this effect purely experimentally is difficult because the typical ballistic set up does not allow control over the yaw angle of the projectile. In this study, a numerical model is used complementing ballistic experiments for a range of yaw angles. For the projectile, a validated computer model of the 30-06 7.62 x 63mm AP M2 round was selected. Surrogate targets were used for a qualitative assessment of the phenomenon. The utilized target is a flat rectangular tile. To encourage yaw in the experimental tests, targets were positioned at relatively close distance to the breach and impact velocity was chosen lower than typical for the projectile. Both ensure that the bullet does not reach stable flight therefore yaw is present. From the experiments, a range of impact velocities and yaw angles was chosen and each of the test conditions simulated. The decrease in bullet velocity ΔV was calculated from high speed video footage captured during tests and compared to bullet ΔV in simulation. Strain condition, predicted damage and negative pressure output from simulation were investigated in pursue of yaw effects on threat level. The results of this study can help in the interpretation of physical test results and ultimately can contribute to making the performance of armour systems more robust