18420 research outputs found
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A Facile Synthesis of 4-Acylamino-Tetrahydroindazoles via the Ritter Reaction
No full textA new route toward 4-acylamino- and 4-amino-substituted tetrahydroindazoles is disclosed. The
title compounds are obtained in good to excellent yields in the Ritter reaction between 4-hydroxy-tetrahydroindazoles
and various nitriles. The reactivity of the tetrahydroindazole-derived carbenium ion is
both sufficiently high to react with trichloroacetonitrile and sufficiently selective to resist the azide
functionality within its structure. The present approach adds a method to the toolbox of tetrahydroindazole
chemistry and facilitates the structural modifications of the scaffold, which has found important
applications in medicinal chemistry
Nanostructured Intermetal-Ceramic Coatings for Blades of Gas Turbine Engines
No full textThe paper deals with the creation of fundamentally new functional
multicomponent coatings applying the technologies of ion-plasmous sputtering.
The results of the conducted experimental research showed the high efficiency
of the elaborated multicomponent intermetal-ceramic (IMCER) coating for the
protection of gas turbine engines (GTE) blades in their maintenance process. The
coating is formed in plasma from the fusions based upon aluminium and titanium.
The maximum thickness of the coating reaches 40 mm
Dynamic Management of Power System Sustainable Development with application for Smart Grids
No full textThe dynamic management of power system development with preconditions required for realization of Smart Grid Technologies (SGT) with attention on sustainability of development concepts on transmission level are presented in the Article as contribution to the research, which is based on the new energy policy of the European Union in vision of a smart grids, to develop and deploy more reliable, secure, economical, efficient, safety, and environmentally friendly electric syste
Assessment of Wind Production Impacts to a Power System and Market Formation in Baltic
No full textThis paper is related to an actual problem of expanding wind production integration to the power system and electricity markets. The model for simulation of wind production curves according to development of wind capacities in Baltic is proposed. In order to evaluate the effect of the wind power integration to the price formation as well as level of system penetration by wind, methodology and algorithms which taking into account development scenarios in Baltic are presented
Influence of Raw Materials Ratio and Sintering Temperature on the Properties of the Refractory Mullite-Corundum Ceramics
No full textThe alumosilicate ceramics with mullite crystalline phase are used in various branches of science and technique. The mullite refractory ceramics with high porosity serve as a heat insulator and as well as a constructional materials. The purpose of the work was to sinter high porosity ceramic and to increase the quantity of mullite phase in this mullite, mullite-corundum ceramics. Two types of compositions were prepared during the experiment. The first type was the compositions with commercial alumina and silica oxides. The second type was from mixing these oxides with 10, 20 and 30 wt% of kaolin. In all samples the Al2O3 and SiO2 were in 2.57:1 ratio, because that was conformed to mullite stechiometric compositions (3Al2O3.2SiO2). The types of alumina oxides were α-Al2O3 (d50=4µm) and γ-Al2O3 (d50=80µm). Ratios of α-: γ-Al2O3 were (1:1) or (1:3). The porous materials were prepared by slip casting of suspension of raw materials. The aluminium paste (0.18 wt%) was used as a pore former. Water content in the suspensions was 30-47 wt%. Pore formation occurred as a result of hydrogen formation in chemical reaction between aluminium paste and water. The samples were sintered at the temperature of 1650°C and 1750°C for one hour. The increasing amount of kaolin, α-: γ-Al2O3 at the ratio (1:3) and sintering at the highest temperature raised the quantity of mullite phase. The mullite phase began to dominate over the corundum phase
Influence of Kaolin and Firing Temperature on the Mullite FormationiIn Porous Mullite-Corundum Materials
No full textThe refractory ceramic became very important in both the traditional and the advanced materials applications as it has outstanding thermal and mechanical properties. The refractoriness of ceramics is achieved by getting the mullite-corundum. Refractory ceramics with high porosity serve as a heat insulator and constructional material. The aim of this work is to get, on the one hand, the refractory ceramics with high porosity and mechanical strength and, on the other hand, small shrinkage of material. Mullite formation in materials is carried out by using in corresponding ratio kaolin, alumina and silica as raw materials [1]
Svārstību slāpētājsistēmas analīze un pielietojums
No full textDarbā detalizēti apskatīts noregulētās masas svārstību slāpētāju aprēķins. Tika izpētīts, par cik var samazināt horizontālos pārvietojumus, no vēja slodzes, ierīkojot monolīta dzelzsbetona augstceltnē ar iekšējo kodolu, un pa perimetru izliktām kolonām dažādas masas svārstību slāpētājsistēmas
Pensiju fondi - tautsaimniecības attīstību veicinošs faktors Latvijā
No full textPublikācijā analizētas pensiju fondu veidošanās problēmas un pensiju reformas loma Latvijas kapitāla tirgū. Pensiju fondos uzkrātais kapitāls tiek akumulēts, koncentrēts un investēts finanšu tirgos - vērtspapīru tirgū un banku kapitāla tirgū.
Raksta autores pievēršas tādām problēmām kā: īstermiņa depozītu dominēšana Latvijas banku noguldījumu struktūrā, kad pieprasīti tiek ilgtermiņa resursi; daļa no pensiju fondos uzkrātā kapitāla var tikt investēta Rīgas Fondu biržā kotētajos vērtspapīros, taču tur trūkst investīcijām pievilcīgu emitentu; paaugstināts pensiju risks esošaiem pensionāriem paaugstināto administratīvo izmaksu dēļ laikā , kad tiek ieviesta jauna pensiju reforma.
Trīs līmeņu pensiju sistēmas ieviešana atrisina virkni problēmu - piesaistot ilgtermiņa kapitālu bankām; iedrošinot lielos uzņēmumus kotēt savas akcijas biržā, u.c
Viedie tīkli un to uzskaite
No full textViedo tīklu definē kā pašdiagnosticējošu tīklu, kas pastāvīgi sūtīs, saņems un apstrādās datus par tīkla un tā atsevišķu elementu stāvokli un parametriem, jaudas plūsmām, kā arī veiks informācijas apmaiņu ar inteliģentām elektroniskām ierīcēm, ražotājiem, operatoriem, tirgotājiem un klientiem
Elektroapgādes sistēmas drošums
No full textRaksts apraksta elektroenerģijas piegādes drošuma ietekmējošus faktorus, elektroapgādes pārtraukuma cēloņus, sekas un to uzlabošanas pasākumus. Darbā analīzēti plašāk lietotie drošuma rādītāji ilgstošiem un īslaicīgiem elektroenerģijas piegādes pārtraukumiem, to izmantošanas iespējas