Surface damage from perpendicular and oblique bullet impacts in stone

Controlled experiments were conducted to investigate the surface damage caused by perpendicular and oblique impacts of bullets into sandstone and limestone targets. Individual bullets fired in conditions simulating modern rifles at typical combat distances excavated craters with diameters from 22 to 74 mm and depths from 4 to 24 mm. Limestone target craters were up to twice as large and deep as those in sandstone. These craters have a complex shape consisting of a central excavation surrounded by a shallow dish, compared to the simple bowl shape of most sandstone impacts. Radial fractures extending to the edge of the target block were common in limestone targets. Impacts at an angle of 45° to the surface in both rock types result in asymmetric craters. Two common types of ammunition were compared: the steel-tipped NATO projectile generally produced larger and deeper craters than the projectile that is commonly fired from AK-47 rifles, despite having approximately half the mass of the latter. These results characterise the sort of damage that can be expected at many sites of cultural significance involved in contemporary conflict zones, and have important implications for their conservation.

Proposed Changes to Asphalt Binder Specifications to Address Binder Quality-Related Thermally Induced Surface Damage

Superpave specifications address binder properties that may lead to rutting, transverse cracking, and fatigue damage with varying degrees of success. However, asphalt binder production and formulation has significantly changed and introduced much more variability in relation to quality since the development of the Superpave Performance-Grade system because of economic, technical, and environmental reasons. Consequently, aged-induced surface distresses under combined thermal and traffic loading have become the main challenge for highway agencies. Thermally induced surface deterioration appears in the form of traditional transverse cracking, block cracking, and raveling, or accelerating damage at construction joints. This study evaluated the limitations of the proposed linear viscoelastic (LVE) rheological cracking surrogates, such as ΔTc, R-value, and G-R parameters, and the ability of the Asphalt Binder Cracking Device (ABCD) failure test to overcome these limitations. ABCD is particularly appropriate to rank binder performance because the measured cracking temperature (Tcr) encompasses binder LVE properties, failure strength, coefficient of thermal contraction, and cooling rate. The proposed parameter (ΔTf = Tc(S = 300 MPa) from BBR—Tcr from ABCD) relates the failure temperature to the equi-stiffness temperature and gives credit to well-formulated and compatible polymer-modified binders expected to increase binder strength and strain tolerance. This paper proposes a specification framework based on both ΔTc and ΔTf, universally applicable, regardless of binder composition. Additionally, preliminary purchase specification limits for binders used in surface layers are proposed based on the analysis of 44 binders, 15 with corresponding field performance data. Obviously, as confirmed by a recent stakeholder workshop and industry feedback, these preliminary specification limits need further validation and possible adjustments to account for regional experience and local challenges.

Overview on Study on Properties of Concrete Canvas

Since there is expeditious increase in the materials extensively used in construction, there is a great demand for construction materials in the current generation to follow different conventional methods. There is no provision for very quick and workable concrete installation procedures in the event of an emergency. Concrete as a construction material is well-known around the world, but the hunt to improve its flexibility has always piqued researchers' interest. Although concrete has many advantages, one disadvantage is that it is not flexible when hardened. The rising cost of repair work as a result of weathering, ground surface damage, and seepage in water canals has always been a source of concern. Concrete cloth, a new technology that removes faults from concrete and is flexible and simple to apply, has been invented. Concrete Canvas has a ceramic property which is semi rigid that makes it fire resistant and water proof.

A novel method for diagnosing rolling bearing surface damage by electric impedance analysis

This paper presents a novel condition monitoring method for rolling bearings, based on measuring the electric bearing impedance. The method can diagnose the presence of damage by frequency-domain analysis, and its extension along the raceway by time-domain analysis. The latter enables the assessment of the severity and the progression of bearing damage. A fatigue test shows that the occurrence of pittings in the bearing raceways causes characteristic peaks in the impedance signal, and that the duration of the peaks increases during damage progression. A second test series with artificial damage shows that the duration of the peaks depends on the bearing load and the length of the damage along the raceway and confirms the explanation hypothesis.

TCAD simulations of non-irradiated and irradiated low-gain avalanche diodes and comparison with measurements

In this work, the results of Technology-CAD (TCAD) device-level simulations of non-irradiated and irradiated Low-Gain Avalanche Diode (LGAD) detectors and their validation against experimental data will be presented. Thanks to the intrinsic multiplication of the charge within these silicon sensors, it is possible to improve the signal to noise ratio thus limiting its drastic reduction with fluence, as it happens instead for standard silicon detectors. Therefore, special attention has been devoted to the choice of the avalanche model, which allows the simulation findings to better fit with experimental data. Moreover, a radiation damage model (called “New University of Perugia TCAD model”) has been fully implemented within the simulation environment, to have a predictive insight into the electrical behavior and the charge collection properties of the LGAD detectors, up to the highest particle fluences expected in the future High Energy Physics (HEP) experiments. This numerical model allows to consider the comprehensive bulk and surface damage effects induced by radiation on silicon sensors. By coupling the “New University of Perugia TCAD model” with an analytical model that describes the mechanism of acceptor removal in the multiplication layer, it has been possible to reproduce experimental data with high accuracy, demonstrating the reliability of the simulation framework.

Complex Material and Surface Analysis of Anterolateral Distal Tibial Plate of 1.4441 Steel

Nickel-based austenitic stainless steels are still common for manufacture of implants intended for acute hard tissue reinforcement or stabilization, but the risk of negative reactions due to soluble nickel-rich corrosion products must be considered seriously. Corrosion processes may even be accelerated by the evolution of microstructure caused by excessive heat during machining, etc. Therefore, this study also deals with the investigation of microstructure and microhardness changes near the threaded holes of the anterolateral distal tibial plate containing approx. 14wt.% Ni by composition. There were only insignificant changes of microhardness, grain size, or microstructure orientation found close to the area of machining. In addition, wettability measurements of surface energy demonstrated only minor differences for bulk material and areas close to machining. The cyclic potentiodynamic polarization tests were performed in isotonic physiological solution. The first cycle was used for the determination of corrosion characteristics of the implant after chemical passivation, the second cycle was used to simulate real material behavior under the condition of previous surface damage by excessive pitting corrosion occurring during previous polarization. It was found that the damaged and spontaneously repassived surface showed a three-time higher standard corrosion rate than the “as received” chemically passivated surface. One may conclude that previous surface damage may decrease the lifetime of the implant significantly and increase the amount of nickel-based corrosion products distributed into surrounding tissues.

Effects of Acid Treatment on The Recovery of Outdated Pre-preg Composite Fibers

Purpose Carbon fiber, Kevlar® fiber, and glass fiber are the most widely used polymer prepregs in manufacturing high-performance composites to produce vital parts for a wide range of applications. The production of carbon and Kevlar® fibers is an energy-intensive process, requiring 198–595 MJ to produce 1 kg of virgin carbon fiber. However, chemically recycling these expired prepregs takes only 38.4 MJ/kg, which could be significantly sustainable. The work described in this study involves an array of experiments involving acid treatment of outdated prepreg composite fibers to study its effects and reclaim the fibers for future applications.Method The experiments were carried out at two different temperatures: 25°C and also 60°C. Sulfuric acid, nitric acid, acetone, and distilled water were used in the process, with varying treatment times of 60, 120, 240, 360, and 420 seconds. The recovered fibers were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Result The optimum treatment time and temperature were different for all three types of fibers. Initially, the glass fiber yielded promising results at room temperature and with a minimal 120-s processing time. Carbon fiber treatment was successful at 60°C with a 420-s treatment time. However, some surface damage was observed in the Kevlar® fiber at 60°C. Conclusion The chemical recycling process is the most sustainable, energy- and cost-efficient approach compared to all other available recycling processes. Also, it is possible to recover much cleaner fibers with the weave intact with an acid treatment and solvent-based recovery.

Evaluation of the Clinical Characteristics of Dry Eye Secondary to Different Types of Liver Diseases

PurposeComparing the clinical characteristics of dry eye secondary to primary biliary cholangitis (PBC), drug-induced liver injury (DILI) and viral hepatitis B(HBV) to evaluate the ocular surface damage caused by different types of liver diseases.Methods32 patients with secondary dry eye, included 10 cases of PBC, 10 cases of DILI and 12 cases of HBV. All patients were evaluated by SPEED questionnaire, corneal fluorescein staining(CFS), non-invasive tear breakup time(NIBUT), Schirmer I test(SIt), tear meniscus height test(TMH), the area of meibomian glands dropout(MG dropout) , partial blinking rate(PBR) and lipid layer thickness(LLT).ResultsCompared with DILI and HBV groups, PBC group had a lower SPEED questionnaire score, but the difference was not statistically significant (F=0.83, P=0.45); the CFS score was higher (c2=7.16,P=0.03), the PBR was higher (F=14.34, P=0.00), the SIt was lower (F=4.30,P=0.02), and the differences were statistically significant. The TMH of PBC and DILI groups was significantly lower than HBV group, and the difference was statistically significant (F=4.15, P=0.02). Compared with PBC group, the LLT of DILI group decreased, the difference was statistically significant (P=0.03). The NIBUT of three groups was lower than normal, but there was no statistical difference between groups (Ff=1.35,Pf=0.27;Fa=2.03,Pa=0.14).The area of meibomian glands dropout of three groups had mild to moderate defects, but there was no significant statistical difference between groups (F=0.32, P=0.73).ConclusionsThe PBC group was more prone to aqueous-deficient dry eye. The DILI group was more prone to obstructive meibomian gland dysfunction (MGD).The HBV group was more prone to non-obstructive MGD. The symptoms of dry eye in the PBC group are mild to moderate discomfort, but the degree of corneal damage is higher, indicating that the corneal sensitivity is reduced, which may be related to the high rate of partial blinking.