scholarly journals A Comparison of the Effects of Ultrasonic Cavitation on the Surfaces of 45 and 40Kh Steels

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 138
Author(s):  
Dmitriy S. Fatyukhin ◽  
Ravil I. Nigmetzyanov ◽  
Vyacheslav M. Prikhodko ◽  
Aleksandr V. Sukhov ◽  
Sergey K. Sundukov
Keyword(s):  
Surface Properties ◽  
Structure Refinement ◽  
Structural Steels ◽  
Ultrasonic Cavitation ◽  
Internal Stresses ◽  
Surface Erosion ◽  
Limiting State ◽  
Geometric Properties ◽  
Third Stage ◽  
Time Required

The ultrasonic treatment of metal products in liquid is used mainly to remove various kinds of contaminants from surfaces. The effects of ultrasound not only separate and remove contaminants, they also significantly impact the physical–mechanical and geometric properties of the surfaces of products if there is enough time for treatment. The aim of this study was to compare the dynamics of ultrasonic cavitation effects on the surface properties of 45 (ASTM M1044; DIN C45; GB 45) and 40Kh (AISI 5140; DIN 41Cr4; GB 40Cr) structural steels. During the study, changes in the structure, roughness, sub-roughness, and microhardness values of these materials were observed. The results showed significant changes in the considered characteristics. It was found that the process of cavitation erosion involves at least 3 stages. In the first stage, the geometric properties of the surface slightly change with the accumulation of internal stresses and an increase in microhardness. The second stage is characterized by structure refinement, increased roughness and sub-microroughness, and the development of surface erosion. In the third stage, when a certain limiting state is reached, there are no noticeable changes in the surface properties. The lengths of these stages and the quantitative characteristics of erosion for the considered materials differ significantly. It was found that the time required to reach the limiting state was longer for carbon steel than for alloy steel. The results can be used to improve the cleaning process, as well as to form the required surface properties of structural steels.

Studies on the life-history of Bunostomum phlebotomum (Railliet, 1900), a hookworm parasite of cattle

Parasitology ◽  
1946 ◽  
Vol 37 (3-4) ◽  
pp. 192-201 ◽  
Author(s):  
J. F. A. Sprent
Keyword(s):  
Infective Larva ◽  
Stage Larva ◽  
Fourth Stage ◽  
Larval Stages ◽  
The Third ◽  
Third Stage ◽  
History Of ◽  
Time Required ◽  
Cutaneous Blood ◽  
Fourth Stage Larva

A description is given of the processes of copulation, formation of the egg and spermatozoon, cleavage, embryogeny and hatching in B. phlebotomum. These processes were found to be essentially similar to those in other strongyle nematodes.The anatomy of the first three larval stages is described and the observations of Conradi & Barnette (1908) and Schwartz (1924) were largely confirmed.Penetration of the skin of calves by the infective larva was observed histologically. The larvae were found to have reached the dermis within 30 min. and to have penetrated the cutaneous blood vessels within 60 min. of application to the skin. The larvae were found in the lung where the third ecdysis was in progress 10 days after penetration of the skin. A description is given of the growth of the third-stage larva in the lung, the changes which take place during the third ecdysis, and the anatomy of the fourth-stage larva.The fourth-stage larvae exsheath in the lungs and travel to the intestine. After a period of growth in which sexual differentiation takes place, the fourth ecdysis occurs and the adult parasite emerges. The time required for the attainment of maturity was found to be somewhere between 30 and 56 days after penetration of the skin.This paper was written at the Ministry of Agriculture and Fisheries Veterinary Laboratories, Wey-bridge, and the writer would like to express his gratitude to the Director, Prof. T. Dalling, also to Dr W. R. Wooldridge, chairman of the Council of the Veterinary Educational Trust for their help and encouragement. The writer's thanks are also due to Dr H. A. Baylis, Prof. R. T. Leiper and Dr E. L. Taylor for their advice and help on technical points, and to Mr R. A. O. Shonekan, African laboratory assistant, for his able co-operation.

Some problems of assessing the dynamic crack resistance of structural steels

2021 ◽  
Vol 18 (3) ◽  
pp. 428-435
Author(s):  
Vladimir I. SMIRNOV ◽  
◽  
Tatiana A. KNOPOVA ◽  
Sergey S. MAYER ◽  
◽  
...  
Keyword(s):  
Crack Resistance ◽  
High Speed ◽  
Dynamic Testing ◽  
Practical Importance ◽  
Dynamic Strength ◽  
Structural Steels ◽  
Dynamic Crack ◽  
Unstable Fracture ◽  
Structural Elements ◽  
Limiting State

Objective: Solving the problem of determining the conditions for the onset and development of unstable fracture, which is extremely important for the development of methods for calculating the limiting states of structural elements, improving the dynamic testing schemes of materials and classifying steels according to their ability to resist fracture. Methods: Analytical methods for assessing the limiting state of structural elements are used. Results: A brief overview of the available test methods for structural steels for dynamic strength and crack resistance is given. The experience accumulated by domestic and foreign practices in testing steels for strength and crack resistance under high-speed loading is analyzed. The disadvantages of the existing methods for assessing the indicators of dynamic strength and resistance to brittle fracture are indicated. Practical importance: It is shown that along with the traditional methods for assessing strength based on safety factors, it is necessary to develop and apply new methods for assessing the limiting state of structural elements, including by the criteria of crack resistance

scholarly journals POST PARTUM HEMORRHAGE;

2017 ◽  
Vol 24 (09) ◽  
pp. 1347-1353
Author(s):  
Sardar Alfareed Zafar ◽  
Asim Shaukat ◽  
Ayesha Khalid ◽  
Ammara Niaz ◽  
Shagufta Noor
Keyword(s):  
Medical Therapy ◽  
Post Partum ◽  
Young Patients ◽  
Reproductive Capacity ◽  
Cross Sectional ◽  
Vaginal Deliveries ◽  
Future Fertility ◽  
Third Stage ◽  
Conventional Medical Therapy ◽  
Time Required

Primary postpartum hemorrhagic, rightly called as obstetrician’s nightmare,refers to excessive blood loss of more than 500ml during the third stage of labour or in the first24 hours after delivery. It continues to be one of the leading causes of maternal mortality andmorbidity all over the world including Pakistan where it is responsible for 21-31% of maternalmortality and morbidity. Objectives: Objective of study was to determine the efficacy of balloontamponade in the management of primary PPH, so that a low cast, easy to use technology isavailable for conserving future fertility by treating postpartum hemorrhage. Settings: Departmentof Gynae & Obs, Allied Hospital, Faisalabad. Study Design: Descriptive cross sectional study.Study Period: 6 months from 1st Oct, 2015 to 31st March, 2016. Material & Methods: All patientsdelivered vaginally at term (after 37 completed weeks of gestation) who developed PPH due touterine atony after failure of conventional medical therapy were included in this study. Patientselection was based on inclusion and exclusion criteria. Their demographic profile and efficacyof balloon tamponade was checked in terms of time required to control hemorrahage andneed of laparotomy. Results: During study period total no. Of vaginal deliveries were 3000.Out of these 298 developed PPH, 220 had PPH due to uterine atony and did not respond toconventional medical therapy. The age of patients ranged between 22 and 40 years with meanage of 30 year (±4.88SD). The parity of the patients ranged between 1 and 14 with the meanparity of 4 (±2.26SD). The condom catheter was introduced in all the selected 80 patients andwas successful in 73 patients. Conclusions: In developing countries such as Pakistan wherethe maternal death rate from PPH is very high, this safe, in expensive and easy procedure (itdoes not require any expertise) can be applied in any situation to save a life and to save theuterus in young patients to conserve reproductive capacity and prevent them from surgery andits morbidity. This will protect the patients from irreversible shock and even death with a successrate of 85-95%.

On the long-term evolution of an intense localized divergent vortex on the beta-plane

2000 ◽  
Vol 422 ◽  
pp. 249-280 ◽  
Author(s):  
G. M. REZNIK ◽  
R. GRIMSHAW ◽  
E. S. BENILOV
Keyword(s):  
Time Scale ◽  
Near Field ◽  
Relative Vorticity ◽  
Translation Speed ◽  
Ocean Eddies ◽  
Second Stage ◽  
Third Stage ◽  
Typical Time ◽  
Vortex Size ◽  
Time Required

The evolution of an intense barotropic vortex on the β-plane is analysed for the case of finite Rossby deformation radius. The analysis takes into account conservation of vortex energy and enstrophy, as well as some other quantities, and therefore makes it possible to gain insight into the vortex evolution for longer times than was done in previous studies on this subject. Three characteristic scales play an important role in the evolution: the advective time scale Ta (a typical time required for a fluid particle to move a distance of the order of the vortex size), the wave time scale Tw (the typical time it takes for the vortex to move through its own radius), and the distortion time scale Td (a typical time required for the change in relative vorticity of the vortex to become of the order of the relative vorticity itself). For an intense vortex these scales are well separated, Ta [Lt ] Tw [Lt ] Td, and therefore one can consider the vortex evolution as consisting of three different stages. The first one, t [les ] Tw, is dominated by the development of a near-field dipolar circulation (primary β-gyres) accelerating the vortex. During the second stage, Tw [les ] t [les ] Td, the quadrupole and secondary axisymmetric components are intensified; the vortex decelerates. During the last, third, stage the vortex decays and is destroyed. Our main attention is focused on exploration of the second stage, which has been studied much less than the first stage. To describe the second stage we develop an asymptotic theory for an intense vortex with initially piecewise-constant relative vorticity. The theory allows the calculation of the quadrupole and axisymmetric corrections, and the correction to the vortex translation speed. Using the conservation laws we estimate that the vortex lifetime is directly proportional to the vortex streamfunction amplitude and inversely proportional to the squared group velocity of Rossby waves. For open-ocean eddies a typical lifetime is about 130 days, and for oceanic rings up to 650 days. Analysis of the residual produced by the asymptotic solution explains why this solution is a good approximation for times much longer than the expected formal range of applicability. All our analytical results are in a good qualitative agreement with several numerical experiments carried out for various vortices.

Effects of temperature on hatching and development of Nematospiroides dubius in aerated water

1975 ◽  
Vol 49 (4) ◽  
pp. 293-296 ◽  
Author(s):  
R. Murua
Keyword(s):  
Minimum Time ◽  
The Third ◽  
Third Stage ◽  
Nematospiroides Dubius ◽  
Effects Of Temperature ◽  
Time Required

ABSTRACTFresh eggs obtained from female Nematospiroides dubius were cultured at temperatures ranging from 5°C to 33°C. Hatching occurred between 5°C and 30°C; third stage larvae were obtained between 5°C and 25°C. The minimum time required from hatching to development to the third stage was 3.6 days (at 20°C) and the maximum was seven days (at 5°C). Larvae cultured at higher temperatures were smaller than those cultured at lower ones.

scholarly journals The effect of temperature on mobility of Angiostrongylus costaricensis third stage larvae

1999 ◽  
Vol 41 (4) ◽  
pp. 225-228 ◽  
Author(s):  
Lúcia M.Z. RICHINITTI ◽  
Nivaldo A. FONSECA ◽  
Carlos GRAEFF-TEIXEIRA
Keyword(s):  
Mathematical Model ◽  
Room Temperature ◽  
Effect Of Temperature ◽  
Infective Larvae ◽  
Third Stage ◽  
Albino Mice ◽  
Time Required

Third stage larvae (L3) from Angiostrongylus costaricensis were incubated in water at room temperature and at 5 <FONT FACE="Symbol">°</font> C and their mobility was assessed daily for 17 days. Viability was associated with the mobility and position of the L3, and it was confirmed by inoculation per os in albino mice. The number of actively moving L3 sharply decreased within 3 to 4 days, but there were some infective L3 at end of observation. A mathematical model estimated 80 days as the time required to reduce the probability of infective larvae to zero. This data does not support the proposition of refrigerating vegetables and raw food as an isolated procedure for prophylaxis of human abdominal angiostrongylosis infection.

Mycorrhizal chronosequence near Exit Glacier, Alaska

1996 ◽  
Vol 74 (9) ◽  
pp. 1496-1506 ◽  
Author(s):  
D.J. Helm ◽  
E.B. Allen ◽  
J.M. Trappe
Keyword(s):  
Mycorrhizal Fungi ◽  
Woody Plants ◽  
Arbuscular Mycorrhizae ◽  
Mineral Soil ◽  
Picea Sitchensis ◽  
Populus Balsamifera ◽  
Black Cottonwood ◽  
Third Stage ◽  
Successional Stages ◽  
Time Required

Mycorrhizal fungi associated with plant species may change as vegetation develops following disturbance. The objectives of this study were to compare ectomycorrhizae through a chronosequence on deglaciated land from bare mineral soil to mature forest and to determine time required for mycorrhizal formation on natural seedlings. A chronosequence that formed as Exit Glacier retreated enabled us to document changes in mycorrhizae on existing woody plants, including Populus balsamifera ssp. trichocarpa (Torr. & Gray) Hult, (black cottonwood) that dominates the early stages, Alnus sinuata (Regel) Rydb. (Sitka alder) that has few ectomycorrhizal fungal associates, and Picea sitchensis (Bong.) Carr. (Sitka spruce) that typifies late successional stages. Some seedlings of Populus balsamifera became ectomycorrhizal within 3 weeks of germination but most took longer. Although a dark type without clamp connections dominated willows in the second and third stage, it was not a dominant in the first stage and was rare on 1st year seedlings. Ectomycorrhizal types differed among successional stages for Populus balsamifera. Diversity increased from early successional stages to later stages, mostly from an increase in evenness rather than richness. Arbuscular mycorrhizae were not found on any woody plants, although a few herbaceous plants had low infection percentages. Keywords: ectomycorrhizae, chronosequence, Populus, Alnus, Picea, Salix.

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