Mažaanglio konstrukcinio plieno suvirinimo siūlių struktūros ir mechaninių savybių suvi rinant skirtingais būdais tyrimas

Mažaanglio konstrukcinio plieno S235JR+AR (EN 10025 - 2 : 2004) suvirinimo siūlių struktūros, bei mechaninės savybės. Suvirinamo metalo storis buvo 10mm. Bandymai buvo atlikti pagal galiojančius standartus. Ištirta suvirinimo siūlių makro ir mikrostruktūra, nustatytas kietumas skirtingose termiškai paveiktose metalo zonose, bei suvirinimo būdo įtaka siulės smūginiam tąsumuiVytauto Didžiojo universitetasŽemės ūkio akademij

Suvirinimo būdo įtaka slėgiminių vamzdžių suvirinimo siūlės stiprumui

Darbe buvo nagrinėjamos konstrukcinio plieno S355 suvirinto glaistiniais elektrodais, TIG ir kombinuotuoju budų (šaknis suvirinta TIG ir perdengta glaistiniais elektrodais) siūlų kokybė. suvirinimo būdo įtaką siulės stiprumui. Vizualine apžiūra ir radiografinė kontrolė parodė, kad siūlės kokybei didelę jtaką turi medžiagų parinkimas ir suvirintojo kvalifikacija. Kadangi bandinius virino atestuotas suvirintojas tai didesnių defektų, kurie neleistų eksploatuoti gaminio nepastebeta. Kalbant apie siūlės kietumą buvo nustatyta, kad kietumas siulės viršuje ir apačioje skiriasi nežymiai, tuo tarpu tarp suvirinimo būdų pastebeti akivaizdūs kietumo skirtumai. Tempimo ir lenkimo bandymai išryškino TIG suvirinimo būdo pranašumą prieš siūles, kuriose buvo virinta glaistiniais elektrodaisVytauto Didžiojo universitetasŽemės ūkio akademij

Device ensuring effective usage of photovoltaics for water heating

The integration of photovoltaic devices (PV) into the network could ensure the efficient use of solar energy. Nevertheless, when using PV systems for water heating, the main problem arises: if a heating element is directly connected to a solar module without using a device that regulates the supply of electric energy to the electric heating element in the boiler, the usage of photoelectric module becomes inefficient. When solar raying is small, the module current becomes equal to the current of the short circuit and the decrease in voltage in the heating element reduces the voltage in the solar module to almost zero. Therefore, it is not advisable to connect solar modules directly to electric heating elements. This study presents Nectar Sun—a device that provides the necessary connection. Nectar Sun is a DC to DA converter, which operates on the basis of a micro-switch, uses maximum power point tracking technology and regulates the supply of electricity to the heating element by pulse-width modulation. These qualities highly improve the characteristics of PV systems. When lighting is equal to 400 W/m2, without Nectar Sun regulator, the voltage of one module will approximately be 22 V, current—3.4 A and power—75 W. When Nectar Sun controller is added, it produces maximum power point (MPP) regime with Umax ≈ 30 V, Imax ≈ 3.2 A and Pmax ≈ 96 W. The usage of PV module power in this point is 100%. The maximum power under lighting 800 W/m2 is about 190 W. The usage of PV module power in this point is equal to about 90%. Electric heating elements under 220 V are 1.5 kW, 2 kW and 3 kW PE (nominal power), with Umax ≈ 124 V (total voltage of four PV modules in the MPP) which will accordingly be 480 W, 640 W and 1120 W PE power. Each PV module gets 1/4 of this power, which is equal to 50%, 65% and 115% of its PmaxJoint Stock Company “Saules graza”, Vilnius, LithuaniaVytauto Didžiojo universitetasŽemės ūkio akademij

Joint surfaces pathology treatment with Pridie drilling

This is an article of two homogenic groups treatment comparison, with 25 patients in each. Between 1998 and 2001 twenty-five patients underwent osteochondral or chondral fragment excision with Pridie tunelisations and 25 patients (controls) – osteochondral/chondral fragment excision alone (O-CFE). Average follow-up was 12.4 (range 10–14 months) and 23.6 months (range 22–25 months). All patients were younger than 30 years of age. Patients were evaluated through ICRS and modified HSS scales, arthroscopicaly, histologically and with x-rays. A blinded research assistant performed all follow-up evaluations. Sixteen of 25 (64%) tunelised (Pridie) results were good and 9 (36%) – fair at the time of last follow-up. Twelve of 25 (48%) in O-CFE group results were good and 12 (48%) – fair 23.6 months post operations. Final modified HSS evaluation showed statistically significantly better results in the Pridie group at the 12.4 and 23.6 months (p=0.005). Last follow-up showed deterioration in both groups (p<0.05). At an average 23.6 months follow-up x-rays showed initial osteoarthritis signs in the knees. Consequently, we recommend Pridie tunelisation procedure until final indications of cartilage grafting techniques will be established