scholarly journals Use of Ice Covers for Transportation

1971 ◽  
Vol 8 (2) ◽  
pp. 170-181 ◽  
Author(s):  
L. W. Gold
Keyword(s):  
Thermal Stress ◽  
Elastic Foundation ◽  
Elastic Plate ◽  
Maximum Stress ◽  
Theoretical Calculations ◽  
Strength Properties ◽  
Vehicle Speed ◽  
Vehicular Traffic ◽  
Total Load

Observations are reported on the failure and use of freshwater ice covers for vehicular traffic. The study showed that good quality ice covers can support loads of up to P = 250 h2, where P is the total load in pounds and h is the thickness of the ice in inches. Failures were reported, however, for loadings as low as P = 50 h2. Factors contributing to the failure of covers for loading less than P = 250 h2 were: vehicle speed, thermal stress due to drop in temperature, and fatigue and quality of the cover. The results are discussed with reference to Westergaard's equations for the maximum stress due to circular loads on an elastic plate resting on an elastic foundation. Information is presented on the elastic and strength properties of ice covers required for theoretical calculations. Experience in the construction and use of ice roads and parking areas is described.

scholarly journals Theoretical and Experimental Fatigue Strength Calculations of Lips Compensating Circumferential Backlash in Gear Pumps

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 251
Author(s):  
Piotr Osiński ◽  
Grzegorz Chruścielski ◽  
Leszek Korusiewicz
Keyword(s):  
Maximum Stress ◽  
Theoretical Calculations ◽  
Fatigue Loading ◽  
Minimum Thickness ◽  
Bending Tests ◽  
External Gear Pumps ◽  
Gear Pumps ◽  
In Series ◽  
Number Of Cycles ◽  
Technical Solutions

This article presents theoretical and experimental calculations of the minimum thickness of a compensation lip used in external gear pumps. Pumps of this type are innovative technical solutions in which circumferential backlash (clearance) compensation is used to improve their volumetric and overall efficiency. However, constructing a prototype of such a pump requires long-lasting research, and the compensation lip is its key object, due to the fact that it is an element influenced by a notch and that it operates in unfavorable conditions of strong fatigue stresses. The theoretical calculations presented in this article are based on identifying maximum stress values in a fatigue cycle and on implementing the stress failure condition and the conditions related to the required value of the fatigue safety factor. The experimental research focuses on static bending tests of the lips as well as on the fatigue loading of the lips in series of tests at increasing stress values until lip failure due to fatigue. The tests allowed the minimum lip thickness to be found for the assumed number of fatigue cycles, which is 2.5 times the number of cycles used in wear margin tests.

scholarly journals Improvements in the profiles and distributions of nitric acid and nitrogen dioxide with the LIMS version 6 dataset

2010 ◽  
Vol 10 (10) ◽  
pp. 4741-4756 ◽  
Author(s):  
E. Remsberg ◽  
M. Natarajan ◽  
B. T. Marshall ◽  
L. L. Gordley ◽  
R. E. Thompson ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Nitrogen Dioxide ◽  
Theoretical Calculations ◽  
Spin Splitting ◽  
Oxides Of Nitrogen ◽  
Polar Night ◽  
Chemical Effects ◽  
Satellite Sensors ◽  
Precision And Accuracy

Abstract. The quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) nitric acid (HNO3) and nitrogen dioxide (NO2) profiles and distributions of 1978/1979 are described after their processing with an updated, Version 6 (V6) algorithm and subsequent archival in 2002. Estimates of the precision and accuracy of both of those species are developed and provided herein. The character of the V6 HNO3 profiles is relatively unchanged from that of the earlier LIMS Version 5 (V5) profiles, except in the upper stratosphere where the interfering effects of CO2 are accounted for better with V6. The accuracy of the retrieved V6 NO2 is also significantly better in the middle and upper stratosphere, due to improvements in its spectral line parameters and in the reduced biases for the accompanying V6 temperature and water vapor profiles. As a result of these important updates, there is better agreement with theoretical calculations for profiles of the HNO3/NO2 ratio, day-to-night NO2 ratio, and with estimates of the production of NO2 in the mesosphere and its descent to the upper stratosphere during polar night. In particular, the findings for middle and upper stratospheric NO2 should also be more compatible with those obtained from more recent satellite sensors because the effects of the spin-splitting of the NO2 lines are accounted for now with the LIMS V6 algorithm. The improved precisions and more frequent retrievals of the LIMS profiles along their orbit tracks provide for better continuity and detail in map analyses of these two species on pressure surfaces. It is judged that the chemical effects of the oxides of nitrogen on ozone can be studied quantitatively throughout the stratosphere with the LIMS V6 data.

On the Vibration of an Elastic Plate on an Elastic Foundation

1967 ◽  
Vol 42 (5) ◽  
pp. 1202-1202
Author(s):  
David H. Y. Yen ◽  
S. C. Tang
Keyword(s):  
Elastic Foundation ◽  
Elastic Plate

Effect of vehicle speed on the quality of closed-chest compression during ambulance transport

Resuscitation ◽  
2010 ◽  
Vol 81 (7) ◽  
pp. 841-847 ◽  
Author(s):  
Tae Nyoung Chung ◽  
Sun Wook Kim ◽  
Young Soon Cho ◽  
Sung Pil Chung ◽  
Incheol Park ◽  
...  
Keyword(s):  
Chest Compression ◽  
Vehicle Speed ◽  
Closed Chest ◽  
Ambulance Transport

Diameter and strength of Ethiopian pure and cross-breed sheep wool fibers

2021 ◽  
Vol 16 ◽  
pp. 155892502110469
Author(s):  
Dereje Berihun Sitotaw ◽  
Addisu Ferede Tesema ◽  
Adane Haile Woldemariam
Keyword(s):  
Relative Humidity ◽  
Strength Properties ◽  
Wool Fiber ◽  
Main Body ◽  
Body Parts ◽  
Wool Fibers ◽  
Breed Sheep ◽  
Different Parts ◽  
Sheep Wool

The wool fibers fineness and strength have a remarkable role to determine the quality of yarn and the subsequent fabrics. The fineness property of the wool fibers is a crucially important fiber property for grading, classifying, selecting for particular applications such as for suit, blanket, shirt, carpet, and so on. The fineness and strength properties of four indigenous (Menz, Wollo, Farta, Tikur), three exotic (Awasi, Dorper, Corrediale), and four cross-breed (50% Dorper, 50% Awasi, 75% Awsi, Washera/Awasi) sheep wool fibers from the four main body parts (sides, neck, back, and belly) at six teeth removed age of 11 different sheep breeds have been investigated. The samples of wool fibers have been conditioned for 24 h at 20ºC ± 1ºC temperature and 65% ± 2% relative humidity. The specimen for sampling has been determined based on ASTM D2130-01. The results revealed that the fineness and strength of whole fibers taken from different parts of sample sheep varied significantly within the breed and among the breeds. The result revealed that the strength and fineness of the wool fibers have a positive correlation and Ethiopian sheep wool fiber is suitable for numerous types of classical and technical applications.

Explosive Fragmentation of Rock Masses with Heterogeneous Structure

2021 ◽  
pp. 135-138
Author(s):  
B.V. Ekvist ◽  
N.G. Barnov
Keyword(s):  
Geological Structure ◽  
Strength Properties ◽  
Open Pit ◽  
Heterogeneous Structure ◽  
Rock Masses ◽  
Variable Delays ◽  
Explosive Fragmentation ◽  
Complex Geological Structure ◽  
Technical Properties

A method to optimize drilling and blasting parameters with account of the physical and technical properties of rocks within the blasted block is proposed to improve the quality of blasting in open pit mines characterized by complex geological settings. The results of laboratory tests are provided that confirm improvement in the quality of rock sample crushing by blasting charges with variable delays and locations, depending on the strength properties of the samples, relative to blasting charges with unchanged parameters. The proposed method can be used in combination with GPR surveys of the rock mass. Explosive fragmentation of the rock masses with complex structures is characterized with a number of features caused by changes in the strength properties within the blasted block. In order to optimize the fragmentation efficiency of rock masses with complex geological structure, it is required to assess physical and technical properties of rocks and to determine their location and variations of the strength properties within the blasted block. It is possible to quickly assess the physical and technical properties of the blasted rocks using the surface georadar method. The outcome of this method is georeferencing of the reoradar data to the location and properties of the rocks to be blasted, along with the methodology of applying the georadar surveys, selection of the areal assembly type depending on the size and properties of detected jointing, and economic justification of applying this method. The novelty consists in linking the georadar data on the rocks to be blasted with drilling and blasting parameters.

scholarly journals Enhancing packaging board properties using micro- and nanofibers prepared from recycled board

Cellulose ◽  
2020 ◽  
Vol 27 (12) ◽  
pp. 7215-7225
Author(s):  
Ossi Laitinen ◽  
Terhi Suopajärvi ◽  
Henrikki Liimatainen
Keyword(s):  
Choline Chloride ◽  
Cellulose Nanofibers ◽  
Deep Eutectic Solvent ◽  
Strength Properties ◽  
Chemical Pretreatment ◽  
Mechanical Grinding ◽  
Cellulose Microfibers ◽  
Board Strength ◽  
Grinding Time

Abstract In this study, cellulose microfibers and cellulose nanofibers (CNF) prepared from recycled boxboard pulp using a mechanical fine friction grinder were used as reinforcements in a board sheet. Micro- and nanofibers manufactured by mechanical grinding have typically broad particle size distribution, and they can contain both micro- and nano-sized fibrils. Deep eutectic solvent of choline chloride and urea was used as a non-hydrolytic pretreatment medium for the CNF, and reference CNF were used without any chemical pretreatment. The CNF were ground using three grinding levels (grinding time) and their dosage in the board varied from 2 to 6 wt%. The results indicate that the board properties could be tailored to obtain a balance between the processability and quality of the products by adjusting the amount of CNF that was added (2–6 wt%). A preliminary cost assessment indicated that the most economical way to enhance the board strength properties was to add around 4% of CNF with a moderate grinding level (i.e., grinding energy of 3–4 kWh/kg). Overall, the strength properties of the manufactured board sheets improved by several dozen percentages when CNF was used as the reinforcement.

scholarly journals Homogenization of Radial Temperature by a Tungsten Sink in Sublimation Growth of 45 mm AlN Single Crystal

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5553
Author(s):  
Yue Yu ◽  
Botao Liu ◽  
Xia Tang ◽  
Sheng Liu ◽  
Bing Gao
Keyword(s):  
Thermal Stress ◽  
Crystal Growth ◽  
Heat Exchange ◽  
Single Crystal ◽  
Numerical Experiments ◽  
Radial Temperature Gradient ◽  
Radial Temperature ◽  
Large Size ◽  
Sublimation Growth

To reduce the thermal stress during the sublimation growth of 45 mm AlN single crystal, a tungsten sink was put on the top of the crucible lid. Numerical experiments showed that the radial temperature gradient was reduced due to the homogenization effect on temperature as a result of the sink. Therefore, this simple tungsten sink method has the potential to grow large-size AlN ingots with fewer cracks. It also reveals that enhancing the heat exchange of the crucible lid is an effective way to improve the quality of crystal growth.

scholarly journals Influence of Site Conditions and Quality of Birch Wood on Its Properties and Utilization after Heat Treatment. Part I—Elastic and Strength Properties, Relationship to Water and Dimensional Stability

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 189 ◽  
Author(s):  
Vlastimil Borůvka ◽  
Roman Dudík ◽  
Aleš Zeidler ◽  
Tomáš Holeček
Keyword(s):  
Heat Treatment ◽  
Dimensional Stability ◽  
Bending Strength ◽  
Color Change ◽  
Untreated Wood ◽  
Strength Properties ◽  
Treatment Temperature ◽  
Impact Bending ◽  
The Impact

This work deals with the quality of birch (Betula pendula) wood from different sites and the impact of heat treatment on it. Two degrees of heat treatment were used, 170 °C and 190 °C. The resulting property values were compared with reference to untreated wood samples. These values were wood density, compressive strength, modulus of elasticity (MOE), bending strength (MOR), impact bending strength (toughness), hardness, swelling, limit of hygroscopicity, moisture content and color change. It was supposed that an increase in heat-treatment temperature could reduce strength properties and, adversely, lead to better shape and dimensional stability, which was confirmed by experiments. It was also shown that the properties of the wood before treatment affected their condition after heat treatment, and that the characteristic values and variability of birch properties from 4 sites, 8 stems totally, were reflected in the properties of the heat-treated wood. Values of static MOR were the exception, where the quality of the input wood was less significant at a higher temperature, and this was even more significant in impact bending strength, where it manifested at a lower temperature degree. Impact bending strength also proved to be significantly negatively affected by heat treatment, about 48% at 170 °C, and up to 67% at 190 °C. On the contrary, the most positive results were the MOE and hardness increases at 170 °C by about 30% and about 21%, respectively, with a decrease in swelling at 190 °C by about 31%. On the basis of color change and other ascertained properties, there is a possibility that, after suitable heat treatment, birch could replace other woods (e.g., beech) for certain specific purposes, particularly in the furniture industry.

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