INFLUENCE OF POLYMORPHIC TRANSFORMATIONS ON ANISOTROPY OF THE SURFACE ENERGY AND THE WORK FUNCTION OF THE ELECTRON OF LITHIUM

На базе электронно-статистического метода показана связь и проведена оценка поверхностной энергии и работы выхода электрона граней кристаллов лития с учетом дисперсионного, поляризационного и осцилляционного взаимодействия атомов поверхностного слоя. Считалось, что кристаллическая решетка не имеет дефектов. Модифицированы выражения поправок и аналитического соотношения, связывающего работу выхода электрона и поверхностную энергию с учетом типа кристаллической решетки и ориентации граней. Рассчитана работа выхода электрона и поверхностная энергия гладких граней при предельных температурах существования полиморфных фаз лития. Установлено влияние полиморфных превращений и температуры на анизотропию. Температурный коэффициент работы выхода электрона бездефектного кристалла положителен и составляет порядка 0,1-1 мэВ. Результаты расчетов хорошо согласуются с экспериментальными данными для поликристаллов. On the basis of the electronic-statistical method, a relationship is obtained and the surface energy and the work function of the electron of the faces of lithium crystals are estimated, taking into account the dispersion, polarization, and oscillatory interactions of the atoms of the surface layer. It was assumed that the crystal lattice has no defects. The expressions for the corrections and an analytical relationship between the work function of the electron and the surface energy are modified taking into account the type of the crystal lattice and the orientation of the faces. The work function of the electron and the surface energy of smooth faces are calculated at the limiting temperatures of the existence of polymorphic lithium phases. The influence of polymorphic transformations and temperature on the anisotropy is established. The temperature coefficient of the work function of an electron in a defect-free crystal is positive and amounts to about 0,1-1 meV. The calculation results are in good agreement with the experimental data for polycrystals.

Molecular dynamic modeling of thermal hysteresis of gold

Molecular dynamics (MD) modeling of the thermal hysteresis of pure metallic gold (Au) is considered in order to study nonequilibrium processes during melting - crystallization phase transformations, i.e. in the transition from solid to liquid. The results of alternative calculations are presented, in which the thermal hysteresis is obtained. The limiting temperatures of overheating of the solid phase during melting and supercooling of the liquid phase during the crystallization of gold have been obtained. The possibility of the formation of highly superheated metastable states of the solid phase upon rapid heating of Au has been confirmed.

State of the scientific and technical knowledge about limiting temperatures in the Repository Site Selection process of Germany with simultaneous consideration to Europe and other European repository concepts

<p>The Federal Republic of Germany has decided to dispose its high-level radioactive waste in deep geological formations. Three types of host rock are considered: rock salt, clay rock and crystalline rock. The Site Selection Act (StandAG<sup>1</sup>), which came into effect on the 16<sup>th</sup> of May 2017, defines the successive steps of the repository siting process, which has to ensure the best possible safety conditions for a period of one million years. Based on precaution considerations, the StandAG (§27 (4) StandAG) sets a preliminary temperature limit of 100°C at the outer surface of a repository container for the preliminary safety assessment.</p><p>This contribution provides an overview about the state of the scientific and technical knowledge on the limiting temperatures in the repository site selection process of Germany. It also illustrates the different treatments of the definition of temperature limits within other European siting processes. The findings highlight that, in Europe, the proposed criteria which consider temperature at the outer surface of a repository container get more and more into focus of research and discussion especially for the three different types of host rocks.</p><p>After presenting the national regulatory frameworks, this contribution summarizes how the European countries address the different temperature related issues for their site selection, their repository concepts and how in turn these all can influence the German safety case strategy for the German site selection. Not at least, links to site selection criteria in other countries (e.g. USA, Japan, Russia) are provided.</p><p><strong>Reference</strong></p><p><sup>1</sup>  StandAG: Standortauswahlgesetz vom 5. Mai 2017 (BGBl. I S. 1074), das zuletzt durch Artikel 2 Absatz 16 des Gesetzes vom 20. Juli 2017 (BGBl. I S. 2808) geändert worden ist.</p>

Evaluation of the Fire Resistance of H-Section Steel Columns and Beams

Building fires can cause severe damages to not only human life but also building structures. Therefore, every nation requires a building regulation related to fire in aspect of safety of human and structural stability. The structural stability under fire condition can be evaluated by the fire test defined in each nation’s standard. However, the results from the test don’t satisfy the real situations of the building such as fire loads, opening size, loading and boundary condition of structural members, and etc. Meanwhile, performance based fire engineering design is regarded as an alternative evaluation method of fire. The fire engineering method has been regarded as a more rational method than the prescriptive method in terms of accuracy and cost efficiency. Recently, the limit temperature method is regarded as the easiest fire engineering method to evaluate the structural stability under fire. To make the backbone of a specification of limiting temperature method, limiting temperatures of various structural members are required. In this paper, in order to make a database of the limiting temperatures of H-section columns and beams, fire test programs with loading were conducted and the limiting temperatures and fire resistance were derived.

Derivation of Major Factors of Beams Made of H-Sections for Fire Engineering Design

Structural steel has been used to make building structures higher and wider than that constructed with conventional structural materials such as concrete, brick, etc since 1960’s in Korea. But the steel structure has fatal demerits. One is the deteriation of structural performance when exposed to severe fire and the other is rusting. The structural behavior has to be sustained during unexpected fire and this can be done by fire design. The fire design consists of two methods. One is prescriptive and the other is performance-base fire engineering design. Recently, the fire engineering design has become a reasonable alternative against the prescriptive method in the world. But the fire engineering method is now preparing for adoption into Korea building regulation. The main purpose of this paper is to build the databases of fire resistant and limiting temperatures of beams made of H-section and the results from fire tests under loadings showed that the corelations between the limiting temperatures and load ratios applied were in reverse proportion.

Experimental Study on the Fire Resistance of Rectangular Hollow Sections Steel Columns

A fire occurring at a building causes severe damages to its structural members and brings unexpected collapse. Therefore, the building regulation of each nation has to define fire resistance to prevent building collapse due to high temperatures. In general, the fire resistance of each structural member can be evaluated by two methods. One is prescriptive method that is guided by a specific building regulation containing fire resistance examples or by the application of new examples tested fire experimental procedures. The other is performance based fire engineering design. Being an engineered and scientific method, it utilizes the results obtained from the calculation of fire severities, temperatures of members and so on. The easiest way to evaluate the fire resistance of a steel member is to compare its limiting temperature and maximum temperature. Therefore, constructing the database of the limiting temperatures of structural elements is very important in performance based fire engineering design. This paper is to derive the fire resistance and limiting temperatures of rectangular hollow sections under loads.

Experimental Study on Limiting Temperatures of Circular Hollow Sections

Fire resistance is required to sustain the structural stability when building elements are exposed to a severe fire condition. To evaluate the fire resistance of structural members such as columns and beams, fire engineers can apply either prescriptive methods or performance-based fire design. These two kinds of fire resistance evaluation methods have been developed independently and performance fire design consists mainly of an advanced and simple methods. The simple method stipulated in New Zealand and the U.K. use the limiting temperature. The values of the limiting temperatures of structural steel members were shown in the BS, SNZ, etc but the temperatures of individuals were not classified. In general steel columns were made of H-section but recently the hollow section is inclined to increase for its higher resistant of structural stabilities than any other sections. But the hollow section shows different pattern when it carry out the loads in the cold and is expected to show different behavior when it is exposed to fire. Therefore the limiting temperature of the hollow section is required for evaluation of fire resistance. The paper is to make the limiting temperature of the circular hollow section (CHS) with or without filling of concrete and variance of applied loads.