scholarly journals Temperature deformation of frozensoils at sharp change of temperature

2017 ◽  
pp. 66-71
Author(s):  
S. S. Volokhov ◽  
I. N. Nikitin ◽  
D. S. Lavrov
Keyword(s):  
Temperature Change ◽  
Soil Type ◽  
Sudden Change ◽  
Frozen Soil ◽  
Temperature Deformation ◽  
Sharp Change ◽  
Frozen Soils ◽  
One Stage ◽  
Different Types ◽  
Number Of Cycles

The results are described of the study of temperature deformation of different types of frozen soil in the cycles of cooling-heating at sudden change in temperature. The differences in the nature of the temperature deformation at step and one stage temperature change are shown. The dependences are investigated of the temperature deformation of frozen soils on soil type, moisture and total number of cycles of cooling-heating.

scholarly journals A global analysis of the impact of COVID-19 stay-at-home restrictions on crime

2021 ◽  
Author(s):  
Amy E. Nivette ◽  
Renee Zahnow ◽  
Raul Aguilar ◽  
Andri Ahven ◽  
Shai Amram ◽  
...  
Keyword(s):  
Public Space ◽  
Global Analysis ◽  
Sudden Change ◽  
Interrupted Time Series ◽  
Urban Crime ◽  
Substantial Variation ◽  
Different Types ◽  
Time Series Analyses ◽  
The Impact ◽  
At Home

AbstractThe stay-at-home restrictions to control the spread of COVID-19 led to unparalleled sudden change in daily life, but it is unclear how they affected urban crime globally. We collected data on daily counts of crime in 27 cities across 23 countries in the Americas, Europe, the Middle East and Asia. We conducted interrupted time series analyses to assess the impact of stay-at-home restrictions on different types of crime in each city. Our findings show that the stay-at-home policies were associated with a considerable drop in urban crime, but with substantial variation across cities and types of crime. Meta-regression results showed that more stringent restrictions over movement in public space were predictive of larger declines in crime.

scholarly journals Effects of preferential flow on snowmelt partitioning and groundwater recharge in frozen soils

2019 ◽  
Vol 23 (12) ◽  
pp. 5017-5031 ◽  
Author(s):  
Aaron A. Mohammed ◽  
Igor Pavlovskii ◽  
Edwin E. Cey ◽  
Masaki Hayashi
Keyword(s):  
Soil Moisture ◽  
Groundwater Recharge ◽  
Preferential Flow ◽  
Frozen Soil ◽  
Time Lags ◽  
Runoff Generation ◽  
Frozen Ground ◽  
Soil Matrix ◽  
Frozen Soils ◽  
Flow Through

Abstract. Snowmelt is a major source of groundwater recharge in cold regions. Throughout many landscapes snowmelt occurs when the ground is still frozen; thus frozen soil processes play an important role in snowmelt routing, and, by extension, the timing and magnitude of recharge. This study investigated the vadose zone dynamics governing snowmelt infiltration and groundwater recharge at three grassland sites in the Canadian Prairies over the winter and spring of 2017. The region is characterized by numerous topographic depressions where the ponding of snowmelt runoff results in focused infiltration and recharge. Water balance estimates showed infiltration was the dominant sink (35 %–85 %) of snowmelt under uplands (i.e. areas outside of depressions), even when the ground was frozen, with soil moisture responses indicating flow through the frozen layer. The refreezing of infiltrated meltwater during winter melt events enhanced runoff generation in subsequent melt events. At one site, time lags of up to 3 d between snow cover depletion on uplands and ponding in depressions demonstrated the role of a shallow subsurface transmission pathway or interflow through frozen soil in routing snowmelt from uplands to depressions. At all sites, depression-focused infiltration and recharge began before complete ground thaw and a significant portion (45 %–100 %) occurred while the ground was partially frozen. Relatively rapid infiltration rates and non-sequential soil moisture and groundwater responses, observed prior to ground thaw, indicated preferential flow through frozen soils. The preferential flow dynamics are attributed to macropore networks within the grassland soils, which allow infiltrated meltwater to bypass portions of the frozen soil matrix and facilitate both the lateral transport of meltwater between topographic positions and groundwater recharge through frozen ground. Both of these flow paths may facilitate preferential mass transport to groundwater.

scholarly journals Numerical Evaluation of a Light-Gas Gun Facility for Impact Test

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
C. Rahner ◽  
H. A. Al-Qureshi ◽  
D. Stainer ◽  
D. Hotza ◽  
M. C. Fredel
Keyword(s):  
High Velocity ◽  
Numerical Evaluation ◽  
Impact Test ◽  
Experimental Tests ◽  
Reservoir Pressure ◽  
One Stage ◽  
Gas Gun ◽  
Numerical Predictions ◽  
High Velocity Impacts ◽  
Different Types

Experimental tests which match the application conditions might be used to properly evaluate materials for specific applications. High velocity impacts can be simulated using light-gas gun facilities, which come in different types and complexities. In this work different setups for a one-stage light-gas gun facility have been numerically analyzed in order to evaluate their suitability for testing materials and composites used as armor protection. A maximal barrel length of 6 m and a maximal reservoir pressure of a standard industrial gas bottle (20 MPa) were chosen as limitations. The numerical predictions show that it is not possible to accelerate the projectile directly to the desired velocity with nitrogen, helium, or hydrogen as propellant gas. When using a sabot corresponding to a higher bore diameter, the necessary velocity is achievable with helium and hydrogen gases.

Planning for a Disaster

2016 ◽  
pp. 49-69 ◽  
Author(s):  
Carmen Cowick ◽  
Jeff Cowick
Keyword(s):  
Mobile Applications ◽  
Cloud Storage ◽  
New Technologies ◽  
Sudden Change ◽  
Disaster Plan ◽  
Different Types ◽  
The Creation ◽  
Reference Tools

In this paper the authors discuss what a disaster plan entails and the steps that need to be taken for an institution to create such a plan, including taking advantage of all the new opportunities to provide a more comprehensive disaster plan through new technologies such as mobile applications, cloud storage and online reference tools. A disaster is a sudden change of situation, because of this, the planning for such an event needs to be done well ahead of time so that adequate training can be implemented and the response to the disaster can be quick and effective. As much as apathy, avoidance and lack of resources can be excuses as to why we have not created an institutional disaster plan, being prepared and trained to handle the different types of emergency disasters that can befall a library or archive is the best way to ensure that the materials will remain protected and the damage done to them in the case of an actual disaster is minimized. The steps outlined in this chapter will help any library or archive in the creation of a successful disaster plan and help them understand why some disaster plans fail.

Advances in lead-free pyroelectric materials: a comprehensive review

2020 ◽  
Vol 8 (5) ◽  
pp. 1494-1516 ◽  
Author(s):  
Hongying He ◽  
Xin Lu ◽  
Emil Hanc ◽  
Chao Chen ◽  
Hao Zhang ◽  
...  
Keyword(s):  
Potential Energy ◽  
Temperature Change ◽  
Electrical Response ◽  
Functional Materials ◽  
Lead Free ◽  
Comprehensive Review ◽  
Different Types

Pyroelectric materials are important functional materials that can generate an electrical response upon a temperature change. In recent years, significant advances have been achieved in different types of lead-free pyroelectrics and are rising to potential energy-related applications.

Automated Techniques for Estimating Factor VIII Levels in Concentrate Preparations

1975 ◽  
Author(s):  
M. J. Seghatchian ◽  
M. Miller-Anderson ◽  
D. J. Howarth ◽  
Y. Stirling ◽  
M. Brozovic
Keyword(s):  
Factor Viii ◽  
Factor Vii ◽  
Two Stage ◽  
End Point ◽  
One Stage ◽  
Different Types ◽  
Long Course ◽  
Good Agreement

An. automated coagulometer (a modification of Electra 600D) using an optical end-point for clot detection, has been used in both one and twostage methods of assaying factor VIII. Fifity clotting times can be measured in a hour. The methods for which the coagulometer has been used are (1) one-stage assay with kaolin-platelet substitute and haemophilic plasma, (2) one-stage assay with activated cephaloplastin (Dade, Nyegaard) and haemophilic plasma, and (3) two-stage method using combined serum reagent (Diagen). With the first two methods, a shortening of standard and blank clotting times occurred during the hour-long course of the assays (2-5 seconds per hour); this was particularly marked in the presence of kaolin, and due in part to activation of factor VII. With the two-stage method, longer standard and blank clotting times, up to 8 seconds per hour, were often recorded as the assays proceeded. These results emphasize the need to incorporate standards at regular intervals during every run, and to take account of the changes with time that occur.Four different types of concentrate preparations commonly used in the treatment of haemophilia were assayed in two laboratories, each using conventional and automated (Electra 600D) methods. There was good agreement between methods and between laboratories.

scholarly journals Artificial Frozen Soil Bending Test and Bending Property

2020 ◽  
Vol 165 ◽  
pp. 03028
Author(s):  
Liu Tao ◽  
Huang Zhi ◽  
Zheng Zhigang ◽  
Hong Shaoyou ◽  
Li Jia ◽  
...  
Keyword(s):  
Earth Pressure ◽  
Bending Moment ◽  
Freezing Temperature ◽  
Test Methods ◽  
Frozen Soil ◽  
Bending Test ◽  
Frozen Soils ◽  
Temporary Support ◽  
Artificial Freezing ◽  
Ground Method

Artificial freezing ground method has been widely used in tunnels, metro and other projects, in the connecting passage in metro, the artificial frozen soil wall, which is formed by artificial freezing method, is often used as temporary support. The artificial frozen soil wall is in the joint action of pressure and bending moment, for it takes the upper pressure and lateral earth pressure at same time, so there may be tensile stress in the profile, which may cause brittle failure. At present, some scholars have carried out researches on the tensile strength with different test methods, but they are insufficiency and have a certain difference in stress state between the specimen and the actual support structure. A bending test instrument was designed and manufacture, which satisfies the code’s requirements, and reduces the error caused by poor contact between the specimen and loading device. Bending test on artificially frozen soils was launched using this instrument, and the test on influence law of moisture content and freezing temperature on artificially frozen soils’ strength was also launched. The conclusions can provide a reference for design and construction.

scholarly journals Thermal Time Constant of PV Roof Tiles Working under Different Conditions

2019 ◽  
Vol 9 (8) ◽  
pp. 1626 ◽  
Author(s):  
Kurz ◽  
Nawrowski
Keyword(s):  
Energy Balance ◽  
Thermal Resistance ◽  
Temperature Change ◽  
Environmental Parameters ◽  
Thermal Capacity ◽  
Electrical Characteristics ◽  
Legal Regulations ◽  
Temperature Changes ◽  
Different Types ◽  
The Relationship

This paper presents different types of photovoltaic (PV) roof tiles integrating PV cells with roof covering. Selected elastic photovoltaic roof tiles were characterised for their material and electrical characteristics. Practical aspects of using PV roof tiles are discussed, alongside the benefits and drawbacks of their installation on the roof. Thermal resistance, heat transfer coefficient and thermal capacity were identified for elastic PV roof tiles and roof construction built of boards and PV roof tiles, according to valid standards and legal regulations. The resistance–capacity (RC) models of PV roof tiles and roofs are proposed according to the time constants identified for the analysed systems. The energy balance of the studied systems (PV roof tiles alone and the roof as a whole) is presented, based on which temperature changes in the PV cells of the roof tiles working under different environmental conditions were identified. The timing of PV cells’ temperature change obtained by material data and energy balance analyses were compared. The relationship between the temperature change times of PV cells and the thermal resistance and heat capacity of the whole system are demonstrated, alongside environmental parameters.

The Rheology of Frozen Soils

2007 ◽  
Vol 17 (1) ◽  
pp. 12147-1-12147-14 ◽  
Author(s):  
Lukas U. Arenson ◽  
Sarah M. Springman ◽  
Dave C. Sego
Keyword(s):  
Mechanical Response ◽  
Soil Mechanics ◽  
Rheological Behaviour ◽  
Theoretical Models ◽  
Complex Stress ◽  
Frozen Soil ◽  
Future Research ◽  
Frozen Soils ◽  
Current State ◽  
Number Of Factors

Abstract The rheological behaviour of frozen soils depends on a number of factors and is complex. Stress and temperature histories as well as the actual composition of the frozen soil are only some aspects that have to be considered when analysing the mechanical response. Recent improvements in measuring methods for laboratory investigations as well as new theoretical models have assisted in developing an improved understanding of the thermo-mechanical processes at play within frozen soils and representation of their response to a range of perturbations. This review summarises earlier work and the current state of knowledge in the field of frozen soil research. Further, it presents basic concepts as well as current research gaps. Suggestions for future research in the field of frozen soil mechanics are also made. The goal of the review is to heighten awareness of the complexity of processes interacting within frozen soils and the need to understand this complexity when developing models for representing this behaviour.

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