High Dynamic Resistance Research Articles

Computational Mechanics for Turbofan Engine Blade Containment Testing: Fan Case Design and Blade Impact Dynamics by Finite Element Simulations

The harsh environment during airplane take-off and flights with complex operating conditions require a high dynamic and impact resistance capability of airplane engines. The design, development, and performance evaluation of new turbofan engines are generally performed through numerical simulations before a full-scale model or prototype experiment for certification. Simulations of fan blade containment tests can reduce trial–error testing and are currently the most convenient and inexpensive alternative for design; however, certification failure is always a risk if the calibration of material models is not correctly applied. This work presents a three-dimensional computational model of a turbofan for designing new engines that meet the certification requirements under the blade containment test. Two calibrated Johnson–Cook plasticity and damage laws for Ti64 are assessed in a simulation of a turbofan blade containment test, demonstrating the ability of the models to be used in the safe design of aircraft engine components subjected to dynamic impact loads with large deformations and adequate damage tolerance.

Design of Dual-Directional SCR Structure With High Holding Voltage and Low Dynamic Resistance for High Voltage ESD Protection

Design of Dual-Directional SCR Structure With High Holding Voltage and Low Dynamic Resistance for High Voltage ESD Protection

Electron affinity of metal oxide thin films of TiO2, ZnO, and NiO and their applicability in 28.3 THz rectenna devices

The holy grail of achieving efficient operation of infrared (IR) rectennas continues to be the realization of a high performance rectifier. In this paper, we have fabricated metal–insulator–metal (MIM) diodes based on TiO2, ZnO, and NiO thin films using shadow mask evaporation, photolithography, and sputtering. The electron affinities of oxides have been measured by a combination of variable angle spectroscopic ellipsometry and x-ray photoelectron spectroscopy, as well as deduction from the extraction of metal/oxide barrier heights of Fowler–Nordheim tunneling plots. Our results confirm a low value for the electron affinity of NiOx of ∼2.1–2.5 eV, which correlates with the high zero-bias dynamic resistance (RD0) of ∼500 kΩ of an associated MIM diode. These values render NiOx to be unsuitable for use in a rectenna device. Better performance has been observed from diodes based on TiO2 and ZnOx films. The best rectification performance was achieved for a Au/2.6 nm ZnOx/Cr diode, scaled down to 1 μm2 device area, showing a zero-bias dynamic resistance of RD0 = 71 kΩ, zero-bias responsivity β0 = 0.28 A/W, and a coupling efficiency of ηc = 2.4 × 10−5% for rectification at 28.3 THz. The main significance of this study is that it employs a methodology whereby key parameters of the MIM stack are derived from physical measurements, which are then used to assist in the fitting of electrical current–voltage data to produce a reliable appraisal of diode performance in an IR rectenna.

THE RELATIONSHIP BETWEEN THE MECHANICAL PROPERTIES OF ARMOR STEEL AND ITS BALLISTIC RESISTANCE (overview)

The relevance of the work. Today the industry is actively developing in the field of manufacturing means for protection of all types of armored vehicles against fire damage by small arms and artillery weapons. At present, ensuring high dynamic resistance of armor against modern weapons without increasing its thickness and, accordingly, the mass of the structure as a whole is achieved due to the use of various non-metallic materials (armor ceramics, high-strength fabrics, etc.) as part of compositions with traditional steel armor. The development and design of workable materials and structures of armor protection is a complex scientific and technical problem. To ensure high stability and survivability of armor, it is necessary to establish a relationship between the mechanical properties of armor steel and its ballistic characteristics. Purpose. Based on the analysis of literary sources, determine the relationship between the mechanical properties of steel armor and its ballistic characteristics. Methodology. The method of scientific and technical literature analysis regarding the requirements for armored obstacles is applied. The results. Analytical investigations of the relationship between the main mechanical properties of steel armor and its ballistic characteristics are conducted in the work, which will allow predicting the optimal combination of mechanical properties’ values that will ensure high ballistic resistance. Increasing the hardness of armor steel usually reduces the impact toughness of steels. It is noted that the ballistic characteristics of structural and armor steels are correlated with the tensile strength limit. The existence of a correlation between the strength properties of materials and their resistance to crack propagation under high-speed (explosive) loading is shown. For a number of materials, there is a close relationship between predicted and measured ballistic characteristics at high deformations associated with ballistic impact, when compressive flow stress is used as a measure of material strength. Increasing impact toughness, especially in high and ultra-high hardness classes, is an important task in the development of armor steel. Hardness limits are therefore set for specific grades of steel armor to control impact toughness during production and reduce the risk of fracture or other brittle damage for specific steel compositions and applications.

Flexible High-Resolution Continuous 3-D Scanning for Large-Scale Industrial Components

Generating a large-scale high-density point cloud is crucial for three-dimensional shape measurements. Both area-scan and line-scan camera systems have advantages and limitations for large-scale structured light measurement. Consequently, we propose a method that achieves complementary advantages of both the camera systems through flexible continuous scanning with high resolution and frequency. For point cloud generation, efficient scanning in continuous motion with high resolution, large field of view, and high frequency is realized using line-scan cameras. A flexible registration strategy without mechanical positioning is proposed for point cloud registration after referring to the registration methods in area-scan camera systems. To realize the above functions, system structure and calibration are designed. Techniques for point cloud generation with high dynamic performance and interference resistance are introduced. The point cloud registration strategy includes methods for high-frequency pose acquisition and processing. Moreover, an optimization method is designed for the point cloud after registration, and the texture is attached. The proposed system has excellent prospects for large-scale industrial component measurements.

Battery State-of-Health estimation based on multiple charge and discharge features

In this work we propose and evaluate the performance of several linear multifeature models for battery State-of-Health estimation. The models combine high current incremental capacity and dynamic resistance features, which can be obtained during partial constant current charge and discharge, respectively. We construct the models by including fixed sets of features or by applying features selection procedures based on statistical criteria. The proposed models are fitted and evaluated with data from three publicly available battery datasets, including batteries cycled using driving, randomised and fast charging profiles. During the test process, we assess the estimation improvement introduced by each multifeature model by evaluating the reduction of the mean squared error in the State-of-Health estimation with respect to two reference single-feature models already used in recent literature. The collinearity is quantified through the variance inflation factor to indicate the prediction reliability of each model. As main result of this analysis, we propose a simple two-features model as the best compromise between estimation improvement with respect single feature models, and collinearity reduction.

The Effect of the Co-Blending Process on the Sensing Characteristics of Conductive Chloroprene Rubber/Natural Rubber Composites.

Three different blending procedures were used to create multiwalled carbon nanotube (MWCNT)-modified chloroprene rubber (CR)/natural rubber (NR) blended composites (MWCNT/CR–NR). The effects of the blending process on the morphology of the conductive network and interfacial contacts were researched, as well as the resistance–strain response behavior of the composites and the mechanism of composite sensitivity change under different processes. The results show that MWCNT/CR–NR composites have a wide strain range (ε = 300%) and high dynamic resistance–strain response repeatability. Different blending procedures have different effects on the morphology of the conductive network and the interfacial interactions of the composites. If the blending procedures have wider conductive phase spacing and stronger interfacial contacts, the change in the conductive path and tunneling distance occurs more rapidly, and the material has a higher resistance–strain response sensitivity.

Feasibility of UHPC shields in spent fuel vertical concrete cask to resist accidental drop impact

Ultra-high performance concrete (UHPC) has been widely utilized in military and civil protective structures to resist intensive loadings attributed to its excellent properties, e.g., high tensile/compressive strength, high dynamic toughness and impact resistance. At present, aiming to improve the defects of the traditional vertical concrete cask (VCC), i.e., the external storage facility of spent fuel, with normal strength concrete (NSC) shield, e.g., heavy weight and difficult to fabricate/transform, the feasibility of UHPC applied in the shield of VCC is numerically examined considering its high radiation and corrosion resistance. Firstly, the finite element (FE) analyses approach and material model parameters of NSC and UHPC are verified based on the 1/3 scaled VCC tip-over test and drop hammer test on UHPC members, respectively. Then, the refined FE model of prototypical VCC is established and utilized to examine its dynamic behaviors and damage distribution in accidental tip-over and end-drop events, in which the various influential factors, e.g., UHPC shield thickness, concrete ground thickness, and sealing methods of steel container are considered. In conclusion, by quantitatively evaluating the safety of VCC in terms of the shield damage and vibrations, it is found that adopting the 300 mm-thick UHPC shield instead of the conventional 650 mm-thick NSC shield can reduce about 1/3 of the total weight of VCC, i.e., about 50 t, and 37% floor space, as well as guarantee the structural integrity of VCC during the accidental drop simultaneously. Besides, based on the parametric analyses, the thickness of concrete ground in the VCC storage site is recommended as less than 500 mm, and the welded connection is recommended for the sealing method of steel containers.

Сучасні перспективні металеві матеріали для бронеперешкод (огляд)

To date, means of protection of all types of armored vehicles against damage by small arms are actively being developed, new grades of steel with increased anti-projectile resistance indicators are being developed, which ensure a reduction in the metal content of structures while simultaneously increasing the tactical and technical characteristics of the product. The constant increase in requirements for the protection of armored vehicles, caused by the improvement of highly effective means of attack, dictates the need to find new approaches to increase the dynamic stability of armored steels using modern metallurgical, material science and construction achievements. The development and design of workable materials and structures of armor protection is a complex scientific and technical problem. The purpose of the work is to determine, based on the analysis of literary sources, the main trends in the development and improvement of modern metal materials for the manufacture of armored obstacles, which have high dynamic resistance against modern highly effective small arms weapons. The paper analyzes the most widely used metal materials for the manufacture of armored barriers, presents information about their advantages and disadvantages, and provides an assessment of the prospects for further development of this industry. It is noted that the current concept of weapons development is aimed at the use of high-tech materials and innovative methods that allow improving protective functions without increasing the mass and dimensions of armor protection. Currently, many different materials are used to create armor protection: metal plates based on steel, titanium, aluminum and their alloys, aramid or polyethylene fibers, as well as ceramics based on boron carbides, silicon, and others. In accordance with the existing concept of increasing the effectiveness of armor protection and ensuring a combination of firepower, security and mobility, the use of promising materials for the creation of armor protection provides an additional reserve for increasing the combat and military-economic efficiency of military equipment.

Effects of High Intensity Dynamic Resistance Exercise and Whey Protein Supplements on Osteosarcopenia in Older Men with Low Bone and Muscle Mass. Final Results of the Randomized Controlled FrOST Study.

The present study aimed to evaluate the effect of high intensity dynamic resistance exercise (HIT-DRT) and whey protein supplementation (WPS) on bone mineral density (BMD) and sarcopenia parameters in osteosarcopenic men. Men ≥ 72 years with osteosarcopenia (n = 43) were randomly assigned to a HIT-RT (HIT-RT: n = 21) or a non-training control group (n = 22). Supervised HIT-RT twice/week was applied for 18 months, while the control group maintained their habitual lifestyle. Supplying WPS, total protein intake amounted to 1.5–1.6 (HIT-RT) and 1.2 g/kg/body mass/d (control). Both groups were supplied with calcium and vitamin D. Primary study outcomes were BMD and the sarcopenia Z-score. After adjusting for multiplicity, we observed significant positive effects for sarcopenia Z-score (standardized mean difference (SMD): 1.40), BMD at lumbar spine (SMD: 0.72) and total hip (SMD: 0.72). In detail, effect sizes for skeletal muscle mass changes were very pronounced (1.97, p < 0.001), while effects for functional sarcopenia parameters were moderate (0.87, p = 0.008; handgrip strength) or low (0.39, p = 0.209; gait velocity). Apart from one man who reported short periods of temporary worsening of existing joint pain, no HIT-RT/WPS-related adverse effects or injuries were reported. We consider HIT-RT supported by whey protein supplementation as a feasible, attractive, safe and highly effective option to fight osteosarcopenia in older men.

Green preparation of transparent superhydrophobic coatings with persistent dynamic impact resistance for outdoor applications

Transparent superhydrophobic surfaces are employed in a wide range of outdoor applications, such as windshields and house windows. However, micro-nano hierarchical superhydrophobic structures are vulnerable to impacts from sand particles and rain drops. The low impact resistance limits the practical applications of superhydrophobic surfaces. Herein, we develop a novel eco-friendly self-assembly process in aqueous medium to construct transparent superhydrophobic surfaces with high dynamic impact resistance. The transmittance of the prepared surfaces was ~ 94.2% compared with the transmittance of the pure glass substrate. The surface is resistant to the impact of 600 g sand and an ~ 8.6 m/s of water jet applied for 6 min (this is nearly 1500 times higher than the annual precipitation in the tropics), which makes the superhydrophobic surface sustainable in heavy rain. Furthermore, the coating was resistant to highly corrosive media (sulfuric acid) in the case of acid rain and UV illumination. A combination of these properties is attractive for transparent applications with self-cleaning properties, waterproofing and environmental stability.

High dynamic resistance elements based on a Josephson junction array.

A chain of superconductor–insulator–superconductor junctions based on Al–AlOx–Al nanostructures and fabricated using conventional lift-off lithography techniques was measured at ultra-low temperatures. At zero magnetic field, the low current bias dynamic resistance can reach values of ≈1011 Ω. It was demonstrated that the system can provide a decent quality current biasing circuit, enabling the observation of Coulomb blockade and Bloch oscillations in ultra-narrow Ti nanowires associated with the quantum phase-slip effect.

A Cryogenic Front-End Preamplifier Operating at 120 K for Bolometric Detector

In this paper, the design and test results of a front-end cryogenic amplifier for a bolometer detector are presented. The amplifier is implemented with two low-noise Si JFETs, where the first FET is configured as a source follower amplifier and the second FET provides a high dynamic resistance to keep the voltage gain very close to unity. A 3 dB bandwidth over a wide range from DC to 10 MHz is achieved in this design. The input voltage noise density is ~ 1.9 nV/√Hz at 300 K, which further reduces to 1.6 nV/√Hz at 120 K. The flicker corner frequency observed is below 50 Hz.

Isometric exercise and pain in patellar tendinopathy: A randomized crossover trial

ObjectivesThe aim of this study was to compare the acute effects of isometric versus dynamic resistance exercise on pain during a pain-provoking activity, and exercise-induced hypoalgesia in participants with patellar tendinopathy. DesignThis study was a pre-registered randomised crossover study. Participants were blinded to the study hypothesis. MethodsParticipants (N = 21) performed a single session of high load isometric resistance exercise or dynamic resistance exercise, in a randomised order separated by a 7-day washout period. Outcomes were assessed before, immediately after, and 45 min post-exercise. The primary outcome was pain intensity scored on a numeric pain rating scale (NRS; 0–10) during a pain-provoking single leg decline squat (SLDS). Secondary outcomes were pressure pain thresholds (PPTs) locally, distally and remotely, as well as tendon thickness. ResultsThere was a significant decrease in pain NRS scores (mean reduction 0.9, NRS 95%CI 0.1–1.7; p = 0.028), and increase in PPTs at the tibialis anterior muscle (mean increase 34 kPa 95%CI 9.5–58.5; p = 0.009) immediately post-exercise. These were not sustained 45 min post-exercise for pain (NRS) or PPTs (p > 0.05). There were no differences between exercise on any outcome. ConclusionsWhile patients with patellar tendinopathy decreased pain during SLDS in response to resistance training, but the magnitude was small. Contraction mode may not be the most important factor in determining the magnitude of pain relieving effects. Similarly, there were only small increases in PPTs at the tibialis anterior which were not superior for isometric exercise.

A New Dual-Direction SCR With High Holding Voltage and Low Dynamic Resistance for 5 V Application

Dual-directional silicon-controlled rectifiers (DDSCRs), which provide both positive and negative electrostatic discharge (ESD) surge paths, are ESD protection devices with an excellent area efficiency. However, DDSCRs have a low holding voltage for use in 5 V-class applications, with a relatively high on-state resistance because of the elongated ESD surge path compared to unidirectional SCRs. In this paper, we propose a novel DDSCR with a higher holding voltage and a better ESD tolerance than conventional low-triggering DDSCRs (LTDDSCRs), realized by operating two additional parasitic bipolar transistors. The proposed ESD protection device was developed through a 0.18- $\mu \text{m}$ CMOS process, and a timeline pulse system was used to verify its properties. The measurement results show that the proposed ESD protection device exhibits an improved tolerance and a high holding voltage and is expected to be reliable in 5 V-class applications

An investigation of Eccentric Versus Concentric Resistance Training on Strength by Movement Velocity and Training Type

It is known that high intensity dynamic resistance training which involves eccentric and concentric contractions is one of the effective method for maximizing strength. Although, it is postulated that eccentric and concentric contractions provide different physiological adaptations, previous studies comparing the short-term effects of these two contractions have reported contradictory findings, with some studies reporting greater strength development with eccentric, some with concentric and some with similar within both training (18). Methodological differences may be of critical importance to the reported different findings, when focusing on the underlying reasons for these effects are discussed. The majority of previous studies on this topic have used isokinetic equipment to compare eccentric with concentric training, however there are also several studies which used isotonic method which is the most common type of resistance training. Since the effects of these two methods can form different physiological adaptations (9), it may not be proper to review the studies related to eccentric and concentric comparisons without taking into account training method variable. In isokinetic, contraction velocity can be controlled by the dynamometer however it is hard to standardize the movement velocity of isotonic training. And also previous studies showed that movement velocity of resistance training may affect strength development (11). At this juncture, the aim of this paper was to review the studies investigating eccentric and concentric resistance training and discuss the reported findings by considering methodological differences (training type and movement velocity). Although it was difficult to present certain implications due to only few studies including same methods in terms of contraction types and training methods, some highlights from this paper can be very informative to further studies. One of them is that the effects of eccentric and concentric resistance training might be different according to training types. The effects of movement velocity of resistance training on strength may also be different in terms of isotonic or isokinetic training methods .

Electrical and Optoelectronic Properties of Chemically Prepared PbS/MnS Heterojunction

Lead sulfide (PbS)/manganese sulfide (MnS) heterojunction is synthesized by a simple two-step chemical bath deposition technique. The as-synthesized heterojunction is studied based on the optical and electrical analyses. The optical absorbance spectrum of the test structure confirms dual peaks at two different wavelengths, which has prompted consideration of the two band gaps of the structure. The origin of dual peaks in the absorbance plot is attributed to the existence of the PbS base layer and the MnS window layer. The band gaps are estimated using the conventional Tauc’s method (Eg = 1.75 eV and 2.9 eV) and also by the absorbance spectrum fitting method (Eg = 1.82 eV and 2.97 eV). In the dc analyses, the PbS/MnS heterojunction possesses low dark current and high dynamic resistance. However, under illumination (400–700 nm) a distinct photo-response is observed, showing a substantial rise in device current with the reduction of dynamic resistance. The photo-response of the heterojunction is examined at 635–699 nm, 514–538 nm and 410–452 nm wavelengths by analyzing the photo-current and photo-resistance. The device is found to be more photosensitive at lower wavelength illuminations compared to the higher wavelength exposures.

Experimental study of a SINIS detector response time at 350 GHz signal frequency

Response time constant of a SINIS bolometer integrated in an annular ring antenna was measured at a bath temperature of 100 mK. Samples comprising superconducting aluminium electrodes and normal-metal Al/Fe strip connected to electrodes via tunnel junctions were fabricated on oxidized Si substrate using shadow evaporation. The bolometer was illuminated by a fast black-body radiation source through a band-pass filter centered at 350 GHz with a passband of 7 GHz. Radiation source is a thin NiCr film on sapphire substrate. For rectangular 10÷100 μs current pulse the radiation front edge was rather sharp due to low thermal capacitance of NiCr film and low thermal conductivity of substrate at temperatures in the range 1-4 K. The rise time of the response was ~1-10 μs. This time presumably is limited by technical reasons: high dynamic resistance of series array of bolometers and capacitance of a long twisted pair wiring from SINIS bolometer to a room-temperature amplifier.

IgA modulates respiratory dysfunction as a sequela to pulmonary chlamydial infection as neonates.

Neonatal Chlamydia lung infections are associated with serious sequelae such as asthma and airway hyper-reactivity in children and adults. Our previous studies demonstrated the importance of Th-1 type cytokines, IL-12 and IFN-γ in protection against neonatal pulmonary chlamydial challenge; however, the role of the humoral arm of defense has not been elucidated. We hypothesized that B-cells and IgA, the major mucosal antibody, play a protective role in newborns against development of later life respiratory sequelae to Chlamydia infection. Our studies using neonatal mice revealed that all WT and IgA-deficient (IgA(-/-)) animals survived a sublethal pulmonary Chlamydia muridarum challenge at one day after birth with similar reduction in bacterial burdens over time. In contrast, all B-cell-deficient (μMT) mice succumbed to infection at the same challenge dose correlating to failure to control bacterial burdens in the lungs. Although IgA may not be important for bacterial clearance, we observed IgA(-/-) mice displayed greater respiratory dysfunction 5 weeks post challenge. Specifically, comparative respiratory functional analyses revealed a significant shift upward in P-V loops, and higher dynamic resistance in IgA(-/-) animals. This study provides insight(s) into the protective role of IgA in neonates against pulmonary chlamydial infection induced respiratory pathological sequelae observed later in life.

HgCdTe e-avalanche photodiode detector arrays

Initial results on the MWIR e-APD detector arrays with 30 μm pitch fabricated on LPE grown compositionally graded p-HgCdTe epilayers are presented. High dynamic resistance times active area (R0A) product 2 × 106 Ω-cm2, low dark current density 4 nA/cm2 and high gain 5500 at -8 V were achieved in the n+-υ-p+ HgCdTe e-APD at 80 K. LPE based HgCdTe e-APD development makes this technology amenable for adoption in the foundries established for the conventional HgCdTe photovoltaic detector arrays without any additional investment.