Effects of ECAE process on the fatigue crack growth rate of copper metal

In this study, the effects of the number of passes performed by the Equal Channel Angular Extrusion as a severe plastic deformation process on copper metal's microstructure and mechanical properties, especially its resistance to fatigue crack growth, have been investigated. The experimental results show that as the number of processes passes increases, the copper metal grains become finer and as a result less stress is concentrated at the starting points of the fatigue fracture, which delays the fracture. For example, after performing 8 ECAE process passes, the threshold values of fatigue crack growth increases by 113.2% relative to the base metal. Moreover, as the grains become smaller, the number of grains and consequently the number of grain boundaries will increase and thus more obstacles will be placed in the way of crack growth. Also, the SEM images indicate that many fine and equiaxed dimples in processed copper become smaller as the number of passes increases. This shows that finer and more equiaxed grains will be obtained by repeating the ECAE process and thus repeating the occurrence of recrystallization. It was cleared that this process improves the mechanical properties of the copper other than the failure strain. However, by increasing the number of process passes, this problem can be significantly reduced. Highlights The fine grains considerably delay the fatigue fracture By ECAE process, the threshold value of fatigue crack growth increases by 113.2% All zones resulting from fatigue fracture are recognizable in fractured ECAE sample The SEM images indicate that a ductile failure has occurred in the tensile samples

Predictors of 30-day mortality after endovascular thrombectomy for large vessel occlusion in the elderly

Objectives Elderly acute ischemic stroke (AIS) patients (≥80 years) would have dismal clinical outcomes even after successful endovascular revascularization for large vessel occlusion (LVO) in the anterior circulation. We aimed to identify predictors of 30-day mortality after endovascular thrombectomy (EVT) in the elderly. Materials and Methods We included older patients who underwent EVT for AIS due to LVO within 6 h after stroke onset in the anterior circulation between 2017 and 2019. Patients due to posterior circulation stroke, with intracerebral hemorrhage (ICH) or pre-stroke modified Rankin Scale (mRS) score of 4 and 5 were excluded. The primary outcome was mortality within 30 days of EVT. The association between clinical, imaging, procedural, follow-up imaging and mortality were analyzed. Successful reperfusion was defined as modified Thrombolysis in Cerebral Infarction (mTICI) score of 2b or 3. Possible predictors of 30-day mortality were assessed by univariate and multivariable logistic regression. Results Total 238 AIS patients eligible for EVT were identified with 58 patients aged 80 years or more. 48 patients met inclusion criteria. Median age was 86 years (age range, 82–102 years). Successful reperfusion was achieved in 38 (79.2%) patients. The 30-day and 90-day mortality rate were 25% and 33.3%, respectively. The independent predictors of 30-day mortality were collateral scores <3 on mCTA (adjusted OR, 16.571; 95% CI, 1.041–263.868; p = 0.047) and number of passes (adjusted OR, 2.475; 95% CI, 1.047–5.847; p = 0.039). Conclusions Lower collateral scores on mCTA and higher number of passes in thrombectomy were independently predictive of 30-day mortality in the elderly.

Rut formation after the passage of logging machinery in spruce forests on binomial soils

Колейность, образующаяся при проходе лесозаготовительной техники во время разработки лесосек при рубке леса, является одним из негативных экологических последствий, связанных с нарушениями почвенно-растительного покрова вырубок, определяющим дальнейшую их реновацию. Негативное влияние от формирования колейности зависит от числа проходов техники и связано с почвенно-климатическими условиями. На опытно-производственном участке ООО «Двинлеспром», территориально расположенном в междуречье С. Двины и Пинеги (Архангельская область, северотаежный лесной район европейской части РФ), изучено влияние разного числа проходов (4, 8, 10) груженого форвадера Ponsse Buffalo King по волоку, не покрытому порубочными остатками. Исходный участок леса представлен ельником черничным V класса бонитета, произрастающим на подзолистой почве на двучленных отложениях, широко распространенных в регионе. На постоянных учетных площадках (20 x 5 м), заложенных в 3 повторениях, провели детальное изучение строения колей, в дне каждой колеи вскрыли почвогрунт и сделали описание горизонтов/слоев почвы, взяли ненарушенные образцы почвы с глубины 0–10 и 10–20 см для определения влажности и плотности сложения. Установлено, что число проходов более определяет глубину, чем ширину колей. Выявлено 6 типов нарушений почвенного покрова по строению почво-грунта на дне колеи, связанных с перемешиванием, сдвиганием и выносом на дневную поверхность оглеенных почвообразующих пород. Показана представленность типов строения дна колеи в зависимости от числа проездов груженого форвардера, а также различия в плотности сложения и влажности почво-грунта. Плотность сложения в толще 0– 20 см при увеличении числа проходов техники закономерно увеличивается до значений, соответствующих почвообразующим породам. При этом доля влаги в толще 0–10 см при увеличении числа проходов повышается, а в толще 10–20 см снижается. Заметные изменения изученных показателей достигаются при восьмикратном проезде груженого форвардера, что позволяет считать это число проездом максимально допустимым на подзолистых почвах на двучленных отложениях в северотаежном лесном районе. The ruts formed after the passage of logging machinery during logging operations are one of the negative environmental consequences associated with disturbances of the soil and vegetation cover of deforestation, which determines their further renovation. The negative impact of the formation of ruts depends on the number of passes of machinery and is associated with soil and climatic conditions. We studied the effect of different number of passes (4, 8, 10) of a loaded Ponsse Buffalo King forvader on a skid trail that is not covered by felling residues. The experimental logging site of LLC Dvinlesprom is located in the watershed between of the Northern Dvina and Pinega (Arkhangelsk region, North Taiga forest region of the European part of the Russian Federation). The original site is represented by a blueberry spruce forest of the V class of bonity, which grows on podzolic soil on binomial deposits and is widely distributed in the region. We laid the permanent accounting pads (20 x 5 m) in 3 repetitions. We conducted a detailed study of the structure of the ruts, at the bottom of each rut, we opened the soil and made a description of the horizons/layers of the soil, took undisturbed soil samples from a depth of 0–10 and 10–20 cm to determine the soil bulk density and moisture content. It was found that the number of passes determines the depth more than the width of the ruts. We identified 6 types of disturbances of the soil cover on the structure of the soil at the bottom of the ruts, associated with mixing, shifting and removal of the gleying soil-forming parent soil to the day surface. We have given the types of the structure of the bottom of the ruts depending on the number of passes of the loaded forwarder, as well as the differences in the soil bulk density and moisture content. The soil bulk density in the thickness of 0–20 cm with an increase in the number of passes of the forwarder naturally increases to the values corresponding to the soil-forming parent soil. At the same time, the proportion of moisture in the thickness of 0–10 cm increases with an increase in the number of passes, and in the thickness of 10–20 cm decreases. Noticeable changes in the studied indicators are achieved with an eight-fold passage of a loaded forwarder, which allows us to consider this number as the maximum permissible passage on podzolic soils on binomial deposits in the north taiga forest area.

The effect of operating parameters of hydrodynamic cavitation – assisted alkaline catalyzed transesterification of sunflower oil with methanol on the degree of triglyceride conversion

The effect of operating parameters such as reaction mixture inlet pressure p 1 (101.3–1013.2 kPa), methanol to oil molar ratio M 1 (3–12), the concentration of catalyst C c (0.0–1.0 wt%), temperature T (25–50 °C) and the number of passes of the reaction mixture through the venturi type hydrodynamic cavitation reactor n (1–12) on alkali-catalyzed transesterification of sunflower oil with methanol assisted by hydrodynamic cavitation (ACTC) on the value of the degree of triglyceride conversion (DTC) was investigated. ACTC was performed by the venturi-type hydrodynamic cavitation reactor (VCR) of our construction. It was found that the values of DTC increase with the increase in p 1, M 1, C c, and n, and decrease with the increase in T. Cavitation yield (CY) values were calculated. The ACTC was proved to be the simplest, fastest, and most highly energy-efficient current technology for the production of biodiesel.

Investigation of the Technological Possibility of Laser Hardening of Stainless Steel 14Cr17Ni2 to a Deep Depth of the Surface

The article presents the results of a research of the process of laser hardening of steel 14Cr17Ni2 (AISI 431) by radiation of a high-power fiber laser LS-16. Assessment of the theoretically possible maximum depth in laser processing without additional beam transformations, the use of additional coatings and devices were shown. The results of experiments on increasing the depth of the hardened layer during laser processing by using scanning of the laser beam and optimally selected mode parameters without scanning are demonstrated. The influence of the number of passes on the depth of the hardened layer is investigated. The microstructure of hardened samples was studied and quantitative estimation of structural components was carried out. The microhardness of hardened samples at different modes of laser hardening was measured.

Influence of soil moisture on energy requirement of rotary tilling

The rotary tiller with ‘L’ shaped blades was examined for torque, power and specific tilling energy requirements to attain optimum soil-machine operational parameters. The three levels of moisture content (11.4%, 12.8% and 14.6% (d.b)), three speed ratios of 20 (?1), 12 (?2) and 9 (?3) at different passes (first, second and third) with rotational speed of 262 rpm were selected for study. The observations indicated inverse relation between torque and power requirement to moisture content. The lowest value of torque of 16.54 N-m and 26.66 N-m was associated with sandy loam and clay loam soil under third pass and moisture content of 14.6 per cent. Similarly, the minimum power requirement of 0.452 kW and 0.699 kW was observed under analogous conditions of rotary tiller. The energy requirement was found to decrease with higher number of passes due to the breakdown of the hard pan and clod aggregate size. The specific tilling energy is strongly correlated with forward speed and less dependent on the number of the passes of rotary tilling.

Groove Formation on Metal Substrates by Nanosecond Laser Removal of Melted Material

An effective strategy to produce grooves on carbon steel substrates by nanosecond laser radiation is proposed. The aim is to increase the productivity of grooves creation. In this study, two different modes of laser treatment are compared. The first mode focuses on the evaporation of material, while the second focuses on the formation of melted material and its removal by the action of pressure vapors produced by evaporated material. Within some ranges of processing parameters, the shape of the groove can be linearly controlled. The dependence of the groove depth also has a logarithmic nature when the number of passes is increased. Using the liquid phase mode in some ranges of parameters can reduce the amount of evaporated material in comparison with standard techniques in which the material is removed in the form of gas, and fine dust is emitted.

The Q and A—The MIVI Q Catheters for Aspiration Thrombectomy—Initial Experience from London

Background: Aspiration thrombectomy is a widely accepted treatment option for large vessel occlusion (LVO). The MIVI aspiration system has a novel design to maximize the lumen size. We present the results of our initial experience with this innovative aspiration thrombectomy system. Materials and Methods: Retrospectively, we reviewed our database to find all cases of LVO treated with the MIVI Q system (February 2019 and July 2020). In addition, we recorded the baseline demographics, NIHSS, ASPECT, mTICI scores, procedural time, complications, and 90 day mRS. Results: Herein, we identified 25 patients with an average age of 65.3 ± 19.3 years (range 19–89), majority of whom were female (n = 14, 56%). The average NIHSS was 16.9 ± 6.7 (range 6–30), and the average CT ASPECT was 7.9 ± 1.4 (range 5–10). The most common clot location was the M1 segment of the MCA (n = 16, 64%). Four of the patients had tandem lesions (16%). The average clot length was 21.7 ± 31 mm (range 2–130 mm). Of the 23 cases where the Q catheter reached the proximal clot face, mTICI ≥ 2b was achieved on the first pass in 11 cases (44%), and at the end of the ‘Q aspiration’ only the procedures with 16 patients achieved mTICI ≥ 2b recanalization (64%). Stent-retrievers were used in 13 cases (52%). At the end of the procedure, 24 patients (96%) achieved mTICI ≥ 2b with 18 patients (72%) achieving mTICI ≥ 2c. The average number of passes with the Q catheter, including when it was used for SOLUMBRA, was 2.1 ± 2.2 (range 1–10). The mean procedure time was 69 ± 32 mins (range 7–116 mins). No complications were associated with the MIVI Q. Conclusions: The MIVI aspiration system is a novel technology with regards to aspiration mechanical thrombectomy. The system is easy to use with early results comparable to other large-bore catheter systems. However, further studies are needed.

A Multi-Tool Analysis to Assess the Effectiveness of Passive Ice Protection Materials to Assist Rotorcraft Manual De-Icing

Search and rescue missions using rotorcrafts need to be reliable all year long, even in winter conditions. In some cases of deployment prior to take off, the crew may need to manually remove accumulated contaminant from the critical surfaces using tools at their disposal. However, icy contaminant may be hard to remove since the rotorcrafts critical surfaces could be cooler than the environment, thus promoting adhesion. Currently, there exists several passive ice protection materials that could reduce the ice adhesion strength and assist the manual de-icing. The aim of this paper is to propose a detailed comparative procedure to assess the ability of materials to assist the manual de-icing of rotorcrafts. The proposed procedure consists of the characterization of materials using several laboratory tests in order to determine their characteristics pertaining to wettability, their icephobic behavior, and finally their assessment under a multi-tool analysis to evaluate if they can assist. The multi-tool analysis uses different mechanical tools, which are currently used during normal operation, to execute a gradual de-icing procedure, which begins with the softest to the hardest tool using a constant number of passes or strokes, under different types of simulated precipitation. Five different materials were used to evaluate the proposed procedure: Aluminum (used as a reference), two silicone-based coatings (Nusil and SurfEllent), an epoxy-based coating (Wearlon), and finally a commercial ski wax (Swix). All of the tested materials could assist the manual de-icing, within a certain limit, when compared to the bare aluminum. However, SurfEllent was the material that obtained the best overall results. This procedure could be easily adapted to different fields of application and could be used as a development tool for the optimization and the assessment of new materials aimed to reduce ice adhesion.

Endobronchial Ultrasound-Guided Transbronchial Needle Aspiration (EBUS-TBNA): Technical Updates and Pathological Yield

Since the endobronchial ultrasound bronchoscope was introduced to clinical practice, endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has become the procedure of choice to sample hilar and mediastinal adenopathy. Multiple studies have been conducted in the last two decades to look at the different technical aspects of the procedure and their effects on the final cytopathological yield. In addition, newer modes of ultrasound scanning and newer tools with the potential to optimize the selection and sampling of the target lymph node have been introduced. These have the potential to reduce the number of passes, reduce the procedure time, and increase the diagnostic yield, especially in rare tumors and benign diseases. Herein, we review the latest updates related to the technical aspects of EBUS-TBNA and their effects on the final cytopathological yield in malignant and benign diseases.