Cross-Section Configuration Coefficient in the Zhurkov’S Generalized Equation

Постановка проблемы. Исследование долговечности строительных материалов с термофлуктуационной позиции является наиболее сложным, но и в тоже время наиболее адекватным методом. Ввиду того, что данная концепция является нечувствительной к изменениям физической структуры, возникает необходимость учета не только материала, но и конфигурации конструкции. Необходимо провести сравнение механизма разрушения при различных вариантах сечения для двух структурно отличающихся элементов - поливинилхлорида (ПВХ) и древесины. Результаты. Для элементов ПВХ и дерева составного сечения в два слоя без специальных связей получен одинаковый коэффициент k = 2. Для элементов составного сечения в три слоя без специальных связей получен коэффициент с интервалом k = 3,5…5,5, что требует дальнейшего уточнения. Выводы. На основе проведенного исследования теоретически обоснованы и экспериментально выявлены закономерности деформирования и разрушения ПВХ-элементов цельного сечения и составного сечения без специального соединения в два и три слоя. Определение термофлуктуационных зависимостей позволяет приблизить теоретические представления о работоспособности строительного материала в конструкции к реальным условиям. Statement of the problem. Studying the durability of construction materials in the aspect of thermal fluctuations is the most complicated, yet the most appropriate method. Considering that this concept does not take into account the changes of the physical structure, it becomes necessary to consider not the material alone but also the configuration of the structure. Therefore it is necessary to make a comparison of two structurally different elements - PVC and wood. Results. The coefficient of the 2-layer composite cross-section (no special connection) is the same for the PVC and wood elements: k = 2. The derived coefficient of the 3-layer composite cross-section (no special connection) is within the following range: k = 3,5…5,5, which requires a more precise definition. Conclusions. Based on the above experiment, we have theoretically established and experimentally confirmed the regularities of deformation and destruction of PVC elements of the 2 and 3-layer solid and composite cross-section without a special connection. Determining the thermal fluctuation relations allows us to bring theoretical concepts of the capacity of the construction material in a structure closer to actual conditions.

Suppressed-moment 2-k order in the canonical frustrated antiferromagnet Gd2Ti2O7

In partially ordered magnets, order and disorder coexist in the same magnetic phase, distinct from both spin liquids and spin solids. Here, we determine the nature of partial magnetic ordering in the canonical frustrated antiferromagnet Gd2Ti2O7, in which Gd3+ spins occupy a pyrochlore lattice. Using single-crystal neutron-diffraction measurements in applied magnetic field, magnetic symmetry analysis, inelastic neutron-scattering measurements, and spin-wave modeling, we show that its low-temperature magnetic structure involves two propagation vectors (2-k structure) with suppressed ordered magnetic moments and enhanced spin-wave fluctuations. Our experimental results are consistent with theoretical predictions of thermal fluctuation-driven order in Gd2Ti2O7, and reveal that inelastic neutron-scattering measurements on powder samples can solve the longstanding problem of distinguishing single-k and multi-k magnetic structures.

A Preliminary Numerical Investigation of Thermal Mixing Efficiency in T-Junctions with Different Flow Configurations

When hot and cold fluids flow through a converging T-junction, rapid temperature fluctuations occur in the mixing region due to the thermal mixing of fluids. This temperature fluctuation causes thermal fatigue, which is responsible for the shortening of service life in a T-junction. Hence, the design of T-junction for thermal mixing requires not only superior mixing performance but minimize thermal fluctuation during mixing is also desirable. The objective of the present paper is to determine the thermal mixing performance at the mixing region of T-junction with two different flow configurations. Water, at different inlet temperatures, is used as a working medium and is assumed incompressible. Two types of flow configurations, namely intersecting and colliding regular T-junction with a sidearm pointing at 12 o’clock position have been evaluated in this paper. Realizable k-epsilon turbulence model was assumed, and its validity benchmarked against RANS and RSM-EB turbulence models. The thermal mixing efficiency of both flow configurations is calculated and compared. The results show that the thermal mixing efficiency of both intersecting and colliding mixing tee increases with the increase of distance and time. Intersecting tee shows higher temperature fluctuation than colliding tee at the mixing outlet, but colliding tee shows higher thermal mixing efficiency than intersecting mixing tee.

Cross-scale Analysis of Temperature Compensation in the Cyanobacterial Circadian Clock System

Clock proteins maintain constant enzymatic activity regardless of temperature, even though thermal fluctuation is accelerated as temperature increases. We investigated temperature influences on the dynamics of KaiC, a temperature-compensated ATPase in the cyanobacterial circadian clock system, using quasielastic neutron scattering. The frequency of picosecond to sub-nanosecond incoherent local motions in KaiC was accelerated very slightly in a temperature-dependent manner. Our mutation studies revealed that internal motions of KaiC include several contributions of opposing temperature sensitivities. To take advantage of this balancing effect, the motional frequency of local dynamics in KaiC needs to exceed ~0.3 ps-1. Some of the mutation sites may be in a pathway through which the motional frequency in the C-terminal domain of KaiC is fed back to the active site of ATPase in its N-terminal domain. The temperature-compensating ability at the dynamics level is likely crucial for circadian clock systems, into which the clock proteins are incorporated, to achieve reaction- or even system-level temperature compensation of the oscillation frequency.

Development of New Design Fatigue Curves in Japan – Treatment of Variable Loading Amplitude Effect

Design fatigue curves of new concept were developed in the Subcommittee on Design Fatigue Curve in the Atomic Energy Research Committee in the Japan Welding Engineering Society (JWES). Also, Working Group on Design Fatigue Curves (WG DFC) in the JSME is studying the validity and the applicability of the design fatigue curves developed in the JWES to incorporate into the JSME Environmental Fatigue Evaluation Method. The developed design fatigue curve consists of the best-fit curves using tensile strength as a parameter, correction of mean stress effect employed the Smith-Watson-Topper approach, surface finish effect and variable loading amplitude effect. This paper discusses the treatment of variable loading amplitude effect in the improved design fatigue curves. The developed design fatigue curves have employed the method of variable loading amplitude effect in EN 13445. This method uses a fatigue life exponent of −0.1 from N = 2 × 106. Research Group on Fatigue Strength in the JSME performed a series of fatigue tests for variable loading amplitude and the test data showed the fatigue life exponent was −0.07. This outcome of the JSME Research Group can support the fatigue life exponent of −0.1 in EN 13445. A survey of the procedure of variable loading effect has been performed on a thermal fluctuation transient at mixed zone of T-junction piping of nuclear power plants for which UF is significantly affected by variable loading effect. Based on this study, the design fatigue curve for variable loading effect that starts from 2 × 106 with the slope of 1/10, which comes from EN 13445-3, can be considered to be applicable to the developed design fatigue curves. Also, the difference of UF between up to 1 × 108 and extension with no limit is relatively small, and the maximum number of cycles of 1 × 108 can be employed for the engineering fatigue analysis.

Effects Of Acclimation, Population, And Sex On Behavioral Thermoregulation, CTMax, Symptoms Of Heat Stress, And Gene Expression of Melanoplus Differentialis, A Generalist Grasshopper - Does Temporal Thermal Heterogeneity Prepare Populations For A Warming World?

Insects thermoregulate using both canalized and plastic mechanisms. Populations of insects utilize these mechanisms to different extents, and while it is posited that the degree of thermal fluctuation a population experiences can determine the optimal combination of mechanisms to utilize, this is still being elucidated. We used three populations of the generalist grasshopper, Melanoplus differentialis (Thomas, 1856), from sites experiencing different degrees of thermal heterogeneity to test for correlations between thermal heterogeneity and 1) behavioral thermoregulation, 2) upper temperature tolerance, 3) the ability to thermally acclimate, and 4) gene expression. We found that 1) behavioral thermoregulation did not differ among sites, 2) CTMax of males, but not females, was higher at more thermally heterogeneous sites, 3) there was acclimation in some of the tested traits, but thermally heterogeneous sites did not always have the most plastic individuals, and 4) there were differences in gene expression among sites, but these differences were not between the most and least thermally heterogeneous sites. We concluded that thermal heterogeneity may play a selective role in some, but not all, of the measured thermoregulatory traits and their plasticity.