Balancing high-speed rotors at low speed using optimized parametric excitation and tuned nonlinear feedback

2021 ◽  
pp. 103873
Author(s):  
A. Dolev ◽  
S. Tresser ◽  
I. Bucher
Keyword(s):  
Parametric Excitation ◽  
High Speed ◽  
Nonlinear Feedback ◽  
Low Speed

scholarly journals Stability of High-Speed Milling

2000 ◽  
Author(s):  
Tamás Insperger ◽  
Gábor Stépán
Keyword(s):  
Parametric Excitation ◽  
Stability Criterion ◽  
High Speed ◽  
Period Doubling ◽  
Flip Bifurcation ◽  
Vibration Frequencies ◽  
High Speed Milling ◽  
Low Speed ◽  
The Stability ◽  
Excitation Model

Abstract The stability charts of high-speed milling are constructed. Non-conventional unstable regions and vibration frequencies are identified. These are related to flip bifurcation, i.e. period doubling vibrations occur apart of the conventional self-excited vibrations typical for turning or low-speed milling with multiple active teeth. A new stability criterion is proposed and applied for the delayed parametric excitation model of milling.

Do You Name Speedy Objects Faster Than Slow Objects: SPEEDED NAMING OR NAMING SPEED? THE AUTOMATIC EFFECT OF OBJECT SPEED ON PERFORMANCE

2018 ◽  
Author(s):  
Moshe Shay Ben-Haim ◽  
Eran Chajut ◽  
Ran Hassin ◽  
Daniel Algom
Keyword(s):  
High Speed ◽  
Mental Representations ◽  
Reading Aloud ◽  
Naming Task ◽  
Naming Speed ◽  
Low Speed ◽  
Everyday Objects ◽  
Pictures And Words

we test the hypothesis that naming an object depicted in a picture, and reading aloud an object’s name, are affected by the object’s speed. We contend that the mental representations of everyday objects and situations include their speed, and that the latter influences behavior in instantaneous and systematic ways. An important corollary is that high-speed objects are named faster than low-speed objects despite the fact that object speed is irrelevant to the naming task at hand. The results of a series of 7 studies with pictures and words support these predictions.

scholarly journals Splatters and Aerosols Contamination in Dental Aerosol Generating Procedures

2021 ◽  
Vol 11 (4) ◽  
pp. 1914
Author(s):  
Pingping Han ◽  
Honghui Li ◽  
Laurence J. Walsh ◽  
Sašo Ivanovski
Keyword(s):  
Particle Size ◽  
Disease Transmission ◽  
High Speed ◽  
Low Speed ◽  
Dental Procedures ◽  
Dental Equipment ◽  
Produce Contamination ◽  
Fluorescein Dye ◽  
Filter Papers ◽  
Airborne Disease

Dental aerosol-generating procedures produce a large amount of splatters and aerosols that create a major concern for airborne disease transmission, such as COVID-19. This study established a method to visualise splatter and aerosol contamination by common dental instrumentation, namely ultrasonic scaling, air-water spray, high-speed and low-speed handpieces. Mock dental procedures were performed on a mannequin model, containing teeth in a typodont and a phantom head, using irrigation water containing fluorescein dye as a tracer. Filter papers were placed in 10 different locations to collect splatters and aerosols, at distances ranging from 20 to 120 cm from the source. All four types of dental equipment produced contamination from splatters and aerosols. At 120 cm away from the source, the high-speed handpiece generated the greatest amount and size (656 ± 551 μm) of splatter particles, while the triplex syringe generated the largest amount of aerosols (particle size: 1.73 ± 2.23 μm). Of note, the low-speed handpiece produced the least amount and size (260 ± 142 μm) of splatter particles and the least amount of aerosols (particle size: 4.47 ± 5.92 μm) at 120 cm. All four dental AGPs produce contamination from droplets and aerosols, with different patterns of distribution. This simple model provides a method to test various preventive strategies to reduce risks from splatter and aerosols.

Nonlinear transport of rarefied Couette flows from low speed to high speed

2020 ◽  
Vol 32 (11) ◽  
pp. 112021
Author(s):  
Jihui Ou ◽  
Jie Chen
Keyword(s):  
High Speed ◽  
Nonlinear Transport ◽  
Low Speed

scholarly journals Energy Absorption Characteristics of PVC Coarse Aggregate Concrete under Impact Load

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Shi Hu ◽  
Huaming Tang ◽  
Shenyao Han
Keyword(s):  
Compressive Strength ◽  
Energy Absorption ◽  
High Speed ◽  
Coarse Aggregate ◽  
Specific Energy Absorption ◽  
Low Speed ◽  
High Speed Impact ◽  
Aggregate Content ◽  
Dynamic Compressive Strength ◽  
Absorption Characteristics

AbstractIn this paper, polyvinyl chloride (PVC) coarse aggregate with different mixing contents is used to solve the problems of plastic pollution, low energy absorption capacity and poor damage integrity, which provides an important reference for PVC plastic concrete used in the initial support structures of highway tunnels and coal mine roadway. At the same time, the energy absorption characteristics and their relationship under different impact loads are studied, which provides an important reference for predicting the energy absorption characteristics of concrete under other PVC aggregate content or higher impact speed. This study replaced natural coarse aggregate in concrete with different contents and equal volume of well-graded flaky PVC particles obtained by crushing PVC soft board. Also, slump, compression, and splitting strength tests, a free falling low-speed impact test of steel balls and a high-speed impact compression test of split Hopkinson pressure bar (SHPB) were carried out. Results demonstrate that the static and dynamic compressive strength decreases substantially, and the elastic modulus and slump decrease slowly with the increase of the mixing amount of PVC aggregate (0–30%). However, the energy absorption rate under low-speed impact and the specific energy absorption per MPa under high-speed impact increase obviously, indicating that the energy absorption capacity is significantly enhanced. Regardless of the mixing amount of PVC aggregate, greater strain rate can significantly enhance the dynamic compressive strength and the specific energy absorption per MPa. After the uniaxial compression test or the SHPB impact test, the relative integrity of the specimen is positively correlated with the mixing amount of PVC aggregate. In addition, the specimens are seriously damaged with the increase of the impact strain rate. When the PVC aggregate content is 20%, the compressive strength and splitting strength of concrete are 33.8 MPa and 3.26 MPa, respectively, the slump is 165 mm, the energy absorption rate under low-speed impact is 89.5%, the dynamic compressive strength under 0.65 Mpa impact air pressure is 58.77 mpa, and the specific energy absorption value per MPa is 13.33, which meets the requirements of shotcrete used in tunnel, roadway support and other impact loads. There is a linear relationship between the energy absorption characteristics under low-speed impact and high-speed impact. The greater the impact pressure, the larger the slope of the fitting straight line. The slope and intercept of the fitting line also show a good linear relationship with the increase of impact pressure. The conclusions can be used to predict the energy absorption characteristics under different PVC aggregate content or higher-speed impact pressure, which can provide important reference for safer, more economical, and environmental protection engineering structure design.

An adaptive sliding mode controller for the lateral control of articulated long vehicles

2018 ◽  
Vol 233 (3) ◽  
pp. 487-515 ◽  
Author(s):  
Naser Esmaeili ◽  
Reza Kazemi ◽  
S Hamed Tabatabaei Oreh
Keyword(s):  
High Speed ◽  
Sliding Mode ◽  
Sliding Mode Controller ◽  
Lane Change ◽  
Lateral Velocity ◽  
Low Speed ◽  
Adaptive Sliding Mode ◽  
Adaptive Sliding Mode Controller ◽  
Articulated Vehicle ◽  
The Stability

Today, use of articulated long vehicles is surging. The advantages of using large articulated vehicles are that fewer drivers are used and fuel consumption decreases significantly. The major problem of these vehicles is inappropriate lateral performance at high speed. The articulated long vehicle discussed in this article consists of tractor and two semi-trailer units that widely used to carry goods. The main purpose of this article is to design an adaptive sliding mode controller that is resistant to changing the load of trailers and measuring the noise of the sensors. Control variables are considered as yaw rate and lateral velocity of tractor and also first and second articulation angles. These four variables are regulated by steering the axles of the articulated vehicle. In this article after developing and verifying the dynamic model, a new adaptive sliding mode controller is designed on the basis of a nonlinear model. This new adaptive sliding mode controller steers the axles of the tractor and trailers through estimation of mass and moment of inertia of the trailers to maintain the stability of the vehicle. An articulated vehicle has been exposed to a lane change maneuver based on the trailer load in three different modes (low, medium and high load) and on a dry and wet road. Simulation results demonstrate the efficiency of this controller to maintain the stability of this articulated vehicle in a low-speed steep steer and high-speed lane change maneuvers. Finally, the robustness of this controller has been shown in the presence of measurement noise of the sensors. In fact, the main innovation of this article is in the designing of an adaptive sliding mode controller, which by changing the load of the trailers, in high-speed and low-speed maneuvers and in dry and wet roads, has the best performance compared to conventional sliding mode and linear controllers.

scholarly journals Mitochondrial-reticular cytostructure in liver cells

1983 ◽  
Vol 214 (3) ◽  
pp. 795-813 ◽  
Author(s):  
J Katz ◽  
P A Wals ◽  
S Golden ◽  
L Raijman
Keyword(s):  
Endoplasmic Reticulum ◽  
High Speed ◽  
Citrate Synthase ◽  
Respiratory Control ◽  
High Salt ◽  
Marker Enzyme ◽  
Salt Medium ◽  
Low Speed ◽  
Low Salt ◽  
Specific Activities

This study examines the structural relationship of mitochondria and the endoplasmic reticulum in liver. Livers of rat and Japanese quail were homogenized and fractionated in media of 0.25 M-sucrose, either 5mM or 50 mM in sodium Hepes [4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid], pH 7.4 (2.2 mM or 22 mM in Na respectively), designated here as low- and high-salt media. Three particulate fractions were prepared by sequential centrifugation. A nuclear pellet sedimenting at 300 g was obtained as described by Shore & Tata [(1977) J. Cell Biol. 72, 714-725], and from the resulting supernatant thereof a low-speed pellet (1100-1500 g) and a high-speed pellet (8000-10 000 g) were prepared. In the low-salt medium the yields of mitochondrial matrix enzymes (citrate synthase, glutamate dehydrogenase, ornithine carbamoyltransferase) and their specific activities in the low-speed pellet were over twice those in the high-speed pellet. In the high-salt medium the yield of matrix enzymes was 4-5 times, and the specific activities were up to 3 times, higher in the low-speed pellet than in the high-speed pellet. Oxygen uptake and respiratory control ratio were also much higher in the low-speed pellets in both media. Some 50-65% of the microsomal marker enzyme glucose 6-phosphatase was in the supernatant from the high-speed pellet, and the rest sedimented with the mitochondria. Repeated washing with the high-salt medium removes only a limited amount of reticulum. Washing with salt-free sucrose removes most of the reticulum, but a fraction remains strongly bound to mitochondria. Homogenates from quail and rat liver were fractioned isopycnically on Percoll gradients in either 0.25 M-sucrose or 0.25 M-sucrose/50 mM-sodium Hepes. Up to five particulate bands were separated and assayed. Mitochondria were present in two to three bands and were associated with endoplasmic reticulum. As seen in the phase-contrast microscope the mitochondria prepared in the low-salt medium consist of separate organelles. In the high-salt medium the mitochondria appear as chains of from three to ten organelles not touching each other. On addition of univalent ions at concentrations above 20 mM, the mitochondria aggregate into chains, and at higher ionic strength larger multidimensional aggregates are formed. The dispersion and aggregation of mitochondria are reversible. Negatively stained electron micrographs reveal a branched mitochondrial structure, with mitochondria held together by strands of reticulum.(ABSTRACT TRUNCATED AT 400 WORDS)

Study on Bonding Properties of Copper and Aluminum in Nano Scale Using Molecular Dynamics Simulation

2012 ◽  
Vol 152-154 ◽  
pp. 183-187 ◽  
Author(s):  
Quang Cherng Hsu ◽  
Yen Yu Cheng ◽  
Bao Hsin Liu
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Bonding Strength ◽  
High Speed ◽  
Tensile Force ◽  
Pure Aluminum ◽  
Pure Copper ◽  
Dynamics Simulation ◽  
Low Speed ◽  
Speed Condition

According to MD simulation results, pressing depth between two bonding materials will affect bonding strength. Alloy material (Al0.9Cu0.1) had void defect phenomenon in low bonding speed condition because the increasing chance of atom migration which will result in low bonding strength. High tensile speed causes material fracture phenomena happen earlier than low speed. Material stress in low speed is smaller than in high speed. Fracture morphology of material is different in different tensile speed. In low speed condition, material can be stretched thinner than in high speed condition. Material in high temperature has greater kinetic energy than low temperature; therefore, material in high temperature has better formability and behaves larger tensile strain than low temperature. For pure aluminum, when temperature raises to 900K which is close to melting point (933K), its crystal structure is no longer belongs to F.C.C. structure, so bonding strength is weaker than low temperature. Large size material has larger contact area than small size material; therefore, the tensile force and tensile strength of the former are larger than the latter. The order of bonding strength for these three materials is: binary alloy > pure copper > pure aluminum.

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