Investigation on Orbital EDM for Double-Hole Thin Wall of Integrated Flexible Joint

The thin neck structure of integrated flexible joint is the key factor to realize high-precision navigation in dynamically tuned gyroscope. The thin neck structure is composed of two adjacent circular holes and the thin wall between the two holes. The thin wall is easy to deform under the external force and vibration exerted by the tool when using traditional machining methods such as drilling and boring, and the cutting tools are easily to be damaged for the machining of small holes in superhard materials, inducing high processing cost. Aiming at these problems, the machining method of double-hole thin wall in the step-by-step orbital electrical discharge machining (EDM) with a high rotation speed electrode is proposed. The procedure for EDM of double-hole flexible thin wall is designed, and the process parameters of each step machining are optimized using orthogonal experiment and signal-to-noise ratio analysis. The machining experiments of double-hole thin wall of 3J33B material are proceed using the optimized parameters. The results show that the hole diameter of the double-hole flexible thin wall is 2 mm, the hole depth is 8mm, and the average thickness of the thin wall is about 46.5 μm. The thickness range between the measured point and the average is 1.55 μm, that compared with average thickness of 46.5 μm, the error is less than 3%, the overall thickness is uniform relatively.

Effect of Cold Rolling on the Microstructure and Mechanical Behaviors of High-Nitrogen and Low-Nickel Alloy

The effects of different cold rolling deformations on the microstructure and mechanical properties of high nitrogen and low nickel alloys were investigated. The microstructure of high nitrogen alloys with different rolling deformations were characterized by EBSD and TEM. The tensile mechanical properties of the high nitrogen alloys at room temperature were tested. The results showed that the microstructure of the cold rolled high nitrogen alloy with deformation of 0% to 70% shows a twinning process. The twin thickness of the high nitrogen alloy without deformation is micron degree. When the rolling deformation is over 50%, the average thickness of the deformation twin is 23nm. When the rolling deformation increases to 70%, the average thickness of the twin is 14nm. When the rolling deformation increases from 0% to 70%, the cold rolled high nitrogen alloy exhibits high strength (1001-2236 MPa) and excellent plasticity (5.9%-64.1%). It is beneficial to have a good combination of strength and plasticity after rolling deformation.

Uji Kinerja Mesin Pengiris dan Pemarut Ganyong (MPPG) Tep-02

Canna (Canna edulis Kerr.) is a type of tuber plant with a fairly high starch content to be used as food. The use of canna is generally processed first into flour. The initial process of flouring canna is done in two ways; the canna plants are sliced and grated. The Department of Agricultural and Biosystem Engineering, Faculty of Agricultural Industrial Technology, University of Padjadjaran, designed the TEP-1902 Canna Slicing and Shredding Machine (MPPG). However, the performance of this machine was not yet known, so testing was needed to determine its performance. The research method used was an experimental method that was analyzed descriptively by measuring, observing, calculating, analyzing, testing, and evaluating the TEP-1902 Canna Slicing and Shredding Machine (MPPG). The results of the performance test of this machine showed that the machine's performance was good, with the following parameters: the actual capacity of the slicing unit and grating unit was 40.95 kg/hour and 182.98 kg/hour, respectively, efficiency was 92.61% slicing and 97.60% grater, the yields were 98.75% slicing and 96.50% grating, respectively, the average thickness of the slices was 2.13 mm, and the uniformity of slice thickness was 65.51%.

The thickness changes of retina in high myopia patients during the third trimester of pregnancy: a pilot study

Objectives To observe and compare the difference in retinal thickness using optical coherence tomography (OCT) between patients with high myopia (HM) during the third trimester of pregnancy and age-matched HM non-pregnant women. Methods A case-control study. A total of 39 eyes from 39 HM women in the third trimester (study group) and 50 eyes of 50 age-matched non-pregnant women with HM (control group) were included. All subjects underwent SD-OCT examination. The built-in software was used to measure the retinal thickness in macular region. The data from two groups were compared using independent-samples t test. Results Among the 89 subjects in this study, the mean gestational age of the study group was 35.09 ± 2.44 weeks, and the average age was 32.24 ± 3.75 years. The average age of the control group was 34.04 ± 7.19 years old. Compared with the control group, the average thickness of parafoveal area, and the average thickness of parafoveal superior, inferior, temporal quadrants of the superficial retina and the average thickness of the foveal and parafoveal of the superficial retina were significantly decreased in the study group (P < 0.05). Compared with the control group, the average thickness of all quadrants of the retina in the parafoveal area except the nasal quadrant were significantly decreased in the study group (P < 0.05). Conclusions In this observational study, the retinal thickness of patients with high myopia during the third trimester of pregnancy was thinner than that of non-pregnant women with age-matched high myopia.

Bonding of Cast Iron-Aluminum In Bimetallic Castings By High Pressure Die Casting Process

A practical bimetallic casting consisting of aluminum matrix and cast iron inserts was manufactured via high pressure die casting (HPDC) process. Different surface treatment methods of the cast iron inserts, including salt membrane plating and electrogalvanizing, were adopted to improve the bonding quality of bimetallic castings. Microstructure characterization on the bonding interface was conducted at different locations of bimetallic castings. Results indicate that compounds with flawless and continuously metallurgical bonding interface can be successfully fabricated by the HPDC process with the zinc rack plating treatment on the surface of cast iron inserts which results in a dense zinc coating with an average thickness of 8 μm. The melt flow speed and heat transition during solidification of the HPDC process are two key factors in determining the bonding integrity of bimetallic castings. With the dissolution and diffusion of the very thin zinc coating during solidification, there is no obvious aggregation of zinc element at the metallurgical bonding interface. Instead, a reaction layer with an irregular tongue-like morphology is formed with an average thickness of approximately 1 μm while it mainly consists of intermetallic phases Al60Cu30Fe10 and Al2FeSi, etc.

Changes in cirrus cloud properties and occurrence over Europe during the COVID-19-caused air traffic reduction

By inducing linear contrails and contrail cirrus, air traffic has a main impact on the ice cloud coverage and occurrence. During the COVID-19 pandemic, civil air traffic over Europe was significantly reduced, in March and April 2020, to about 80 % compared to the year before. This unique situation allows us to study the effect of air traffic on cirrus clouds. This work investigates, based on satellite lidar measurements, if and how cirrus cloud properties and occurrence changed over Europe in the course of COVID-19. Cirrus cloud properties are analyzed for different years between 2014 and 2019, which showed similar meteorological conditions for the month of April as in 2020. The meteorological conditions for March, however, were warmer and drier in 2020 than the previous years. The average thickness of cirrus clouds was reduced to 1.18 km in March 2020 compared to a value of 1.40 km under normal conditions, which is stronger than expected from the aviation reduction due to the less favorable meteorology for ice cloud formation. While the April results in 2020 were only slightly reduced, with an average thickness of 70 m thinner than the composite mean of the previous 6 years. Comparing the different years shows that the cirrus cloud occurrence was reduced by about 17 %–30 %, with smaller cloud thicknesses found in 2020 for both months. In addition, the cirrus clouds measured in 2020 possess smaller values of the particle linear depolarization ratio (PLDR) than the previous years at a high significance level for both months, especially at colder temperatures (T<-50 ∘C). The same analyses are extended to the observations over the USA and China. Besides the regional discrimination of cirrus clouds, we reach the final conclusion that cirrus clouds show significant changes in PLDR in both March and April over Europe, no changes in both months over China, and significant changes only in April over the USA.

Hydro-Geoelectrical Study for Groundwater Potential of Lassa And Environs, North Eastern Nigeria

Twenty-two Vertical Electrical Sounding (VES) were carried out to evaluate groundwater potential and aquifer protective capacity of the overburden units using Schlumberger configuration. It was observed that H-curve is the dominant curve type in the study area. The Geo-electro stratigraphic section revealed that the geologic sequence beneath the study area is composed of topsoil, highly weather basement, partly fractured basement and fresh basement. The first layer has an average thickness and resistivity of 1 m and 130 Ωm, respectively. The second layer has an average thickness of 14 m and an average resistivity of 53 Ωm. The third layer is partly fracture basement with an average resistivity of 747 Ωm while at some VES point represents fresh basement. The highly weathered basement and partly fracture basement layer make up the water bearing formation of the area. Dar-Zarrouk parameter revealed that the area under study has protective capacity range from weak to good capacity of the overburden material. Areas that are classified as poor and weak are indicative areas are thus vulnerable to infiltration of leachate and other surface contaminations. The groundwater potential of the area ranges from low to moderate potential; the moderate zone constitutes 86% while the low potential constitutes 14% of the study area. The transverse resistance within the study area ranges from 119.6 to 6983.7 ohms-m2 with an average value of 1024.59 ohms-m2. Hydraulic conductivity values determined from geoelectrical technique range from 3.05 to 38.04 m/day with an average value of 14.86 m/day.

About the using of Matiegka’s formulas to evaluate the fat component of body mass. Technical recommendations (short communication)

For this work were taken measurements of the skinfolds of Russian children and adolescents of both sexes 7-17 years old, with a total number of 1103 pupils. Was made a comparison of the mean values of the average skinfolds. Results and discussion. In the investigated group significant differences in the average thickness of the skinfolds were revealed between the initial set of Matiegka and the modification of Lutovinova et al. The revealed differences significantly influenced the final estimates of the mass of body fat. However, the estimates obtained turned out to be highly correlated and with a high level of agreement, on the basis of which conversion formulas between them were proposed. Conclusion. When using Matiegka's formulas, it is necessary to give a detailed description of the method for measuring skinfolds, taking into account the influence of the choice of skinfolds on the final estimate of the fat mass.

Experimental Investigation on Granite Cutting by Means of Diamond Frame Saw

A great quantity of granite sawing experiments was carried out to explore the cutting performance offrame sawing machine with the horizontal reciprocating cutting mode.A model of average thickness of cutting chip was established, and characteristics of cutting forces were analyzed. The mechanism of wear was revealed by analyzing the width of the saw kerf and the wear morphology of the diamond segments. The results showed that the wear resistance and the cutting forces ncrease as the feed speed. The cutting forces change abruptly at the reversing point during granite cutting. At the same time, the proportion of macro-fractured and pulled-out particles and the mean wear rate of segments increase with the feed speed, and the mean protrusion height of the grits is less than 100 μm. The width of the saw kerf is gradually reduced as the sawing progresses, forming an inverted cone with a large upper side and a small lower side. Besides, the studies found that the wear of the segments remains consistent in two directions. The prominent phenomenon of the diamond particles on the side surface is more obvious as the feed speed increases.The research can provide certain data support for granite cutting, and lay the foundation for the subsequent optimization of the structure and equipment.

Two-Dimensional Perovskite Crystals Formed by Atomic Layer Deposition of CaTiO3 on γ-Al2O3

CaTiO3 films with an average thickness of 0.5 nm were deposited onto γ-Al2O3 by Atomic Layer Deposition (ALD) and then characterized by a range of techniques, including X-ray Diffraction (XRD) and High-Resolution, Transmission Electron Microscopy (HRTEM). The results demonstrate that the films form two-dimensional crystallites over the entire surface. Lattice fringes from HRTEM indicate that the crystallites range in size from 5 to 20 nm and are oriented in various directions. Films of the same thickness on SiO2 remained amorphous, indicating that the support played a role in forming the crystallites.