Optimization of the drilling-and-blasting process to improve fragmentation by creating of a preliminary stress in a block

At mining and processing complexes, many parameters today are evaluated from the point of view of the total process from geology to the final product. Changes in certain mining parameters inevitable lead to the changes in the following downstream processes. In this article, the focus is on the ore fragmentation, which is one of the most important parameters in many mines as it affects the downstream ore preparation and processing efficiencies, productivities and costs. In most of the cases, the cheapest way to improve the fragmentation of the ore is by changing the drilling-and-blasting design parameters. It of course increases the mining costs, but at the same time decreases the costs of the following processes, which are normally significantly higher. Therefore, authors of this article propose a new way of optimization of the drilling-and-blasting process by introducing new blast design modifications. Based on the analysis, research of the scientific information and the mining practise, the authors discuss the way of creation of the preliminary stress in the block of the open pit and hence improving fragmentation. Physical experimental blasts in “Belaya Gorka” open pit were performed and shown positive results reflecting a potential for continuation of the research in this direction in the future.

Stress-strain behaviour of pre-stressed slabs of off-shuttering formation reinforced by carbon fiber

The paper presents calculations result of an assembled reinforced concrete hollow core slab of off-shuttering formation which has been reinforced with pre-stressed wire in its top and bottom areas reinforced with carbon fiber, in their turn. The research also examines the existing practice of using carbon fiber as reinforcement elements of reinforced concrete structures, existing specification documents regulating carbon fiber application of carbon in the Russian Federation as well as specification documents containing information about carbon fiber strength and stress-strain properties. The article contains the information on the scheme of loading, conditions of the slab fastening, geometrical characteristics of floor slab panels, physical characteristics of concrete and reinforcement of the experimental sample; technical characteristics of carbon reinforcement elements. The research results are represented as graphs of variance of construction deflections under loading in operating conditions of a slab wIth and without cracks before its reinforcement, and also in the moment of reinforcement. The research shows that using of carbon fiber to reinforce flexural elements with preliminary stress allows to increase rigidity and crack resistance of reinforced concrete elements.

Design of the Next Generation Antenna Mounts

Design of new antenna mount with low effective projected area (EPA) and high load carrying capacity for telecommunication towers is discussed in this paper. The main aim is to reduce the EPA of the mount against the wind pressure direction at the desired elevation from ground by reducing the mount frame structure parts compared to the previous mount designs used in the market. The model in itself has to withstand its dead weight, operator’s weight along with five antenna-radio units. The new model has been designed with a single horizontal frame and four supporting structure for EPA reduction and also the EPA is calculated through Image Processing using MATLAB tool which has not been done previously for mounting structures in the telecommunication field. The preliminary stress and deformation results calculated using ANSYS 15.0 tool and future work that has to be carried out for the design are also discussed in this paper.

Application of ASME Piping Code Through a Stress Analysis Procedure and Comparison With the Italian Code

A previously-developed procedure applies to evaporator section of bottom-supported heat-recovery steam generators (HRSG): The procedure features methods to use on pressure internal parts designed according to Section I, as required by the Boiler & Pressure Vessel (B & PV) Code. It uses ASME Power Piping Code B31.1, which is for external piping, to evaluate additional concerns on pressure parts that have already met Section I. This mainly because other sections of B & PV code do not cover flexibility analysis: Procedure includes classical methods for the static analysis of the lower header and a computer-modeled flexibility analysis. They investigate the stability of the harp high-temperature components, which may be critical because of their longitudinal dimensions, thermal expansions and loading: Preliminary stress evaluation showed that Italian pressure formula is largely conservative. Methods’ application to a worked example using both ASME and Italian pressure formulae shows now that the pressure contribution is the greatest. Also, the maximum stress found out on the header in sustained case appears consistent with that from numerical model, though bending contribution the greatest; Sustained case appears less critical than thermal. So, the design should be safe from risks of static instability due to longitudinal pressure stress: deformation occasionally observed in field on the lower headers may be correctly imputed to thermal expansion. Herein, a bottom-supported HRSG double-width unity of combined cycle power plant is considered as the worked example.

ASME Piping Code-Based Stress Analysis Procedure and a Comparison With the Italian Code

The procedure proposed applies to evaporator section of bottom-supported heat-recovery steam generators (HSRG): It includes classical methods for the static analysis of the lower header based on ASME Power Piping code B31.1 [1] and a computer-modeled flexibility analysis with a preliminary stress evaluation using both Italian and ASME pressure formulae. The stability of the harp high-temperature components may be critical because of their longitudinal dimensions, thermal expansions and loading. So, further elements of engineering choices may help obtaining good design of the header-tube assembly (harp).

Viscoelastic Behavior of a Centrally Loaded Circular Film Being Clamped at the Circumference

A new theoretical model is constructed for the viscoelastic response of a clamped circular membrane deformed by a spherical indenter, using the classical Maxwell and Standard Linear Solid (SLS) constitutive equations. Preliminary stress-relaxation experiments are performed for a hydrogel membrane and the corresponding data fitted to the SLS-based viscoelastic model.

Neurological examination in obsessive-compulsive disorder

Recent studies suggest the occurrence of a neurological dysfunction in Obsessive-Compulsive Disorder (OCD). The purpose of the present study was to verify the clinical value of a neurological evaluation in patients with the disease. We submitted 15 patients with OCD (five of whom were under clomipramine) and 15 controls in a detailed neurological examination, including assessment of the neurological soft-signs. Eleven patients (73.3 percent) and four controls (26.7 percent) presented abnormalities on examination. The main findings among the patients were: palmomental reflex (six cases); mirror movements (five cases); agraphestesia and dysdiadochokinesia (three cases). Three out of the four patients who had a normal examination were on clomipramine. Palmomental reflex was the main finding among the controls. These results, although preliminary, stress the interest and usefulness of performing a detailed neurological examination in OCD.