The structural safety of connections with fillet welds

The need to use unsophisticated probability-based approaches and methods in the structural safety analysis of welded connections and joints subjected to extreme loads and other actions is discussed. A limit state criterion of the fillet weld, its normal and shear stresses caused by permanent, sustained and extraordinary variable actions are considered. Stochastic processes and sequences of safety margins of welded connections are analysed. The analysis of instantaneous and time-dependent survival probabilities of welded connections is based on the concepts of conventional resistances and transformed conditional probabilities. The structural safety of beam-to-column connections is analysed and illustrated by a numerical example.     

Design basis of Lithuanian steel and aluminium structure codes and their relations to Eurocode

The background in the development of national building technical regulations for the design of steel and aluminium structures is discussed. National Design Standards are under consideration in comparison with the main concepts of EC3 and EC9. Standard features of design parameters of materials, partial safety factors and metallic cross-sections are considered in this article. The resistance criterion of members in combined compression and bending is analysed. The effect of member slenderness and fillet weld connections on design results given by National technical regulations and Eurocodes is illustrated.     

Estimating the amount of cyan,magenta, yellow,and black inks in arbitrary colour pictures

This paper is concerned with the offset lithographic colour printing. To obtain high quality colour prints, given proportions of cyan (C), magenta (M), yellow (Y), and black (K) inks (four primary inks used in the printing process) should be accurately maintained in any area of the printed picture. To accomplish the task, the press operator needs to measure the printed result for assessing the proportions and use the measurement results to reduce the colour deviations. Specially designed colour bars are usually printed to enable the measurements. This paper presents an approach to estimate the proportions directly in colour pictures without using any dedicated areas. The proportions—the average amount of C, M, Y, and K inks in the area of interest—are estimated from the CCD colour camera RGB (L*a*b*) values recorded from that area. The local kernel ridge regression and the support vector regression are combined for obtaining the desired mapping L*a*b* ⇒ CMYK, which can be multi-valued.     

Current situation of the wind energy use and investigation of wind resources in the coastal region of the Baltic Sea in Lithuania

In this paper current situation and future prospects of the use of wind energy and wind power resource assessment experience in Lithuania are reviewed. Installed wind power capacity has increased from 6.4 to 54.84 MW in Lithuania in 2006. During last five years wind power resource assessment was carried out, wind measurements were generalized and on the basis of obtained results Lithuanian wind resources map was developed. Measurements have shown that the most suitable region for building WT of big capacity is the 10 km wide coastal strip in Lithuania. The suitability of several existing WT sites was evaluated by the power output coefficient, which describes the efficiency of installed WT. The aim of this work is to present the current situation of wind energy development and the results of the investigation of wind climate conditions in the coastal region of the Baltic Sea in Lithuania.     

The resistance of compressed spun concrete members reinforced by high-strength steel bars

The expediency of using precast spun concrete columns and other members of annular cross sections reinforced by high-strength steel bars is discussed. Test material properties and production, curing and testing procedures, response factors and ultimate compressive stresses of plain and reinforced spun concrete specimens are presented. The strength and strain features of compressed tubular reinforced concrete members are considered. Modeling of a bearing capacity of eccentrically loaded members of annular cross sections is based on the concepts of bending with an concentrical force and compression with a bending moment. The comparison of modeling and test data of concentrically and eccentrically loaded members is analysed.     

Assessment of wood fuel use for energy generation in Lithuania

The paper investigates possibilities to use solid biomass (wood) resources. It provides detailed analysis on distribution of Lithuanian wood resources and evaluates possibilities to develop the use of above resources for heat and power generation. European Union as well as Lithuanian legislation declares promotion measures for wood as fuel for energy generation. Legal documents suggest implementation via subsidizing of raw material for production of wood chips for boiler-houses and adopting specific promotion program for the use of forestry biomass for boiler-houses according to which the difference between price and costs should be subsidized for producers of such raw material.Directive 2009/28/EB obligates separate countries to develop National Renewable Energy Action Plans (NREAP), which would provide specific promotion schemes and target indicators for each year (up to year 2020). According to this Directive the EU RES share in final energy consumption should reach 20%, and for Lithuanian this share should be no less than 23%, while district heating systems should use no less than 70%. At present the total capacity of wood-chip-fueled boilers reached above 476.1 MW. No series obstacles can be seen for extension of wood fuel use. The renewable energy compromise 18.1% of primary energy annual gross inland consumption and cut of the CO₂ emissions about 6% compared with the level on 1990. According to the Kyoto Protocol Lithuania must reduced green gas emissions 8% in the period 2008–2012. These goals can be realised by increasing of the use of biomass as fuel for the energy production.     

Passive acoustic monitoring of head disc interface interactions

A hard disc drive (HDD) recording head thermal protrusion is monitored by the passive acoustic characterization technique where adaptive discrete wavelet (ADW) filtering has been introduced to declare the contact. A phenomenological model is built to demonstrate detectability of the passive acoustic monitoring. The model is based on the mechanical impedance approach where impedances of head disc interface (HDI) and acoustic emission (AE) sensor are compared for matching over air bearing/head gimble assembly frequency bandwidth. A synthesized HDI response signal derived from the HDI mechanical impedance function is compared to the real AE signal obtained during the thermal protrusion based contact detection. A methodology of HDD level AE signal characterization presented in this work consists of the ADW filtering technique where the fifth order DB7 wavelet base function is used in AE signal decomposition. The signal decomposition order is selected by the AE signal entropy minimization.     

A novel approach to exploring company’s financial soundness: Investor’s perspective

Prediction of company’s life cycle stage change; creation of an ordered 2D map allowing to explore company’s financial soundness from a rating agency perspective; and prediction of trends of main valuation attributes usually used by investors are the main objectives of this article. The developed algorithms are based on a random forest (RF) and a nonlinear data mapping technique “t-distributed stochastic neighbor embedding”.Information from five different perspectives, namely balance, income, cash flow, stock price, and risk indicators was aggregated via proximity matrices of RF to enable exploration of company’s financial soundness from a rating agency perspective. The proposed use of information not only from companies’ financial statements but also from the stock price and risk indicators perspectives has proved useful in creating ordered 2D maps of rated companies. The companies were well ordered according to the credit risk rating assigned by the Moody’s rating agency.Results of experimental investigations substantiate that the developed models are capable of predicting short term trends of the main valuation attributes, providing valuable information for investors, with low error. The models reflect financial soundness of actions taken by company’s management team. It was also found that company’s life cycle stage change can be determined with the average accuracy of 72.7%. Bearing in mind fuzziness of the transition moment, the obtained prediction accuracy is rather encouraging.     

Phenomenological nanoindentation technique in quality control of optoelectronics devices

Multiphase and porous ceramic materials are being used as passive semiconductors for building modern optoelectronics devices. Prescreening of the critical parts for subsurface defects before assembly can prevent device failures in the field. A new nanoindentation based non-destructive method has been proposed where shapes of loading–unloading curves can fingerprint subsurface cracking and material porosity induced inelastic behavior in defected multiphase, rough and porous ceramic parts. In addition to the differences in nanoindentation loading-unloading curve shapes, nanohardness values associated with the cracked contact surfaces were 40% lower. The non-destructive nanoindentation results agree well with the destructive Knoop’s microhardness results. A commercially available nanoindentation instrument integrated into the tribometer together with high-resolution optical microscope was utilized for automated and qualitative/quantitative surface materials properties characterization of optoelectronics parts. The proposed instrument and nondestructive testing method can be used for quality control of optoelectronics parts before assembly, significantly improving the yields.     

Effect of weld parameters on mechanical properties and tensile behavior of tungsten inert gas welded AW6082-T6 aluminium alloy

The effect of different welding parameters on the mechanical properties and tensile behavior of tungsten inert gas (TIG) welded joints was analyzed. Four different groove angles were chosen, 60°, 70°, 80° and 90°, to ascertain the tendency of microstructure formation and quality of the weld. Mechanical properties were assessed in the terms of Vickers HV1 hardness. Microanalysis of test samples produced using different current 165 A, 180 A, 200 A with same groove angle of 90° was done in fusion, partially melted, and heat affected zone; all the images showed good penetration and clear transition from one to following zone. The transverse tensile tests were accomplished on the welded joints to evaluate influence of welding parameters and groove geometry to the joint tensile strength and its behavior during exploitation. It was verified that the tensile strength of the welds is closely related to the welding parameters. The chosen 180 A welding current ensured highest tensile strength of test samples; the same as proper selection of groove angle (90°) provides good fusion and high quality of major welds. The results revealed that the weld penetration depends on welding current.