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Analysis of Technical Harmonization Approaches: Comparison and Improvement
No full textThe single market ensuring free circulation of goods, services, capital and people is one of the major achievements in Europe nowadays. For its successful existence trade barriers are eliminated, mutual recognition is ensured and technical harmonization – unified requirements for goods being placed on the market – is organized. Solutions of the technical harmonization are – Old Approach, New Approach and Global Approach. Each approach has different requirements.
The goal of the research is to assess and compare approaches of the technical harmonization. As the result of the research the proposals for improvement of the harmonization approaches are put forward
Synthesis of Romancement from Latvia’s Clay and Dolomite
No full textDuring 19th/20th century in territory of Latvia dolomitic romancement was the main hydraulic binder applied for the construction of buildings. It was processed since 1865 by firing local raw material - dolomitic marl below its sintering temperature (800-900ºC) and fine milling. Nowadays there is absence of information about the material characteristics and technologies for its restoration. Moreover, local deposits of dolomitic marl in industrial scale are no more available.
The aim of investigation was to obtain a binder for restoration needs from Latvia’s clay and dolomite compatible with historically used dolomitic romancement.
Mixtures from two types of clay and dolomite in powder state were synthesized. Samples were prepared by mixing the raw materials, semidry pressing and firing at 750-950°C temperatures. Thermochemical processes in dolomite-clay mixtures depending on production temperature and clay type were compared by using XRD analysis and full chemical analysis
Low-Temperature Hydraulic Binders for Restoration Needs
No full textLate 19th/ early 20th century was a period of active usage of low-temperature hydraulic binders, e.g., romancement, for the construction of buildings. Dolomitic romancement was characteristic to Latvia in contrast to rest of Europe, where calcitic romancement was applied. An investigation have been done with the aim to synthesize a binder from local clay and dolomite compatible with historical dolomitic romancement. The results of chemical and XRD phase analyses have approved that Devonian as well as Quaternary period clay in mixture with dolomite can form a binder which closely conforms with historical ones. Obtained compositions can be considered as perspective for restoration needs
Single-Stage Electromagnetic Elevator Modelling in FEMM Software
No full textIn present paper an electromagnetic elevator (conveying device) designed in Riga Technical University (Latvia) is described. Modelling of single-stage electromagnetic elevator in FEMM software is suggested. Analysis of electromagnetic field distribution created by multi-turn coil used as a propulsion mean for conveying of ferromagnetic materials by electromagnetic field is presented. Use of different coil materials and coil dimensions is evaluated
Optimal Design of Composite Plates with Discrete Variable Stiffness
No full textA new optimization technique of composite plates with discrete varying stiffness is proposed. It consists of threemain steps. Analysis of optimal continuous varying bending and shear stiffness of plate is done in the first step by minimizing structural compliance and stress field differences. Size optimization of discrete domains is done in the second step by solving minimization problem with a Genetic Algorithm. Dimension optimization of plates internal structure is done by previously trained feed-forward artificial neural net work in the third step. A simply supported rectangular plate with uniformly distributed load and multi-span plate with concentrated loads are optimized by the using of proposed method. The deflection of optimized plate could be reduced up to 50%, and average increase of strength to mass ratio is about 20%
Glycerol Oxidation by Molecular Oxygen in Presence of Novel Supported Platinum Catalysts
No full textGlycerol is a bio-fuel production by-product. This work studies novel supported Pt contained
catalyst, prepared by extractive-pyrolytic method [1], activity and selectivity in process of glycerol oxidation
in alkaline water solutions. In the process of catalysts preparation the support nature, the time of support
dispersion in the precursor solution, drying temperature, temperature and duration of pyrolysis, as well as Pt
concentration in the catalyst, were varied. Research revealed that catalysts activity and selectivity depends on
catalyst support nature, pyrolysis temperature and duration as well as on Pt concentration in catalyst. The
most active catalysts are Pt/AlO(OH), Pt/ZrO2, Pt/Y2O3, Pt/Lu2O3 and Pt/Al2O3. Depending on the catalyst
composition and its synthesis conditions main oxidation products obtained were either glyceric or lactic
acids
The highest selectivity by glyceric acid 55-61% with glycerol conversion 85-90% has been achieved
by use of 5%Pt/Al2O3 catalyst prepared from precursor with concentration 0.4 M, support dispersion time 10
min, drying temperature 80-100 ºC and time 10 min, pyrolysis temperature and duration are equal
correspondingly 300 ºC and 120 min. Glycerol oxidation conditions: c0(glycerol) = 0.3 M, c0(NaOH) = 0.7-
1.5 M, n(glycerol)/n(Pt) = 210-300, t = 60 ºC, P(O2) = 1 atm, oxidation time is 4-8 hours.
The highest selectivity by lactic acid 63% with glycerol conversion 86% has been achieved by use of
1.25%Pt/Y2O3 catalyst prepared from precursor with concentration 0.4 M, support dispersion time 10 min,
drying temperature 80-100 ºC and time 3 min, pyrolysis temperature and duration are equal correspondingly
400 ºC and 5 min. Glycerol oxidation conditions: c0(glycerol) = 0.3 M, c0(NaOH) = 1.5 M, n(glycerol)/n(Pt)
= 300, t = 60 ºC, P(O2) = 1 atm, oxidation time is 7 hours
Increased Radiation Hardness of CdZnTe by Laser Radiation
No full textThe aim of this work is to study the possibility to increase the radiation hardness of Cd0.9Zn0.1Te crystal using laser radiation. Pulsed Nd:YAG laser for this aim was used. Estimation of the crystalline lattice defects before and after irradiation by γ-ray using photoluminescence method in the experiments was applied. Experimental results showed the increase of the radiation hardness of CdZnTe crystal after irradiation by laser at intensity 1.20-1.80 MW/cm2
Facile Synthesis of Coumarin Bioisosteres—1,2-Benzoxathiine 2,2-Dioxides
No full textA simple and reproducible procedure for the synthesis of bioisosteres of coumarin—1,2-benzoxathiine 2,2-dioxide is presented. The developed method is based on the intramolecular aldol cyclization of derivatives of mesylsalicyl aldehydes in the presence of strong organic bases, where best results were obtained with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). It has been shown that depending on the nature of the substituent in the aromatic ring, intermediate aldol adducts (3,4-dihydro-1,2-benzoxathiin-4-ol 2,2-dioxides) in different ratios with title compound are formed. Dehydration of the intermediate aldols with POCl3 led to full conversion into 1,2-benzoxathiine 2,2-dioxide derivatives. The scaffold of 1,2-benzoxathiine 2,2-dioxide is unequivocally proven by a single-crystal X-ray structure
The Effect of pH on Polymorph Formation of the Pharmaceutically Active Compound Tianeptine
No full textThe anti-depressant pharmaceutical tianeptine has been investigated to determine the dynamics of polymorph formation under various pH conditions. By varying the pH two crystalline polymorphs were isolated. The molecular and crystal structures have been determined to identify the two polymorphs. One polymorph is an amino carboxylic acid and the other polymorph is a zwitterion. In the solid state the tianeptine moieties are bonded through hydrogen bonds. The zwitterion was found to be less stable and transformed to the acid form. During this investigation an amorphous form was identified