0000000000465081
AUTHOR
Oskars Rubenis
Progressive cracking mastercurves of the transverse ply in a laminate
In this study, progressive cracking of a transverse layer in a cross-ply composite laminate subjected to tensile loading is considered. Using the results of a probabilistic cracking model, approximate relations for crack density as a function of stress are derived for initiation-controlled and propagation-controlled cracking. It is shown that the crack density evolution in the transverse ply can be represented by a mastercurve in suitably normalized coordinates. The mastercurve approach is applied to progressive cracking in glass/epoxy laminates. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Clinical measurements with multi-spectral photoplethysmography sensors
A portable multi-spectral photoplethysmography device has been used for studies of 40 subjects. Multi-spectral monitoring was performed by means of a four - wavelengths (465 nm, 530 nm, 630 nm and 870 nm) light emitted diodes (LED) and a single photodiode with multi-channel signal output processing. The proposed methodology and potential clinical applications are discussed.
Multi-spectral photoplethysmography technique for parallel monitoring of pulse shapes at different tissue depths
A photoplethysmography (PPG) signal can provide very useful information about a subject's hemodynamic status in a hospital or home environment. A newly developed portable multi-spectral photoplethysmography device has been used for studies of 11 healthy subjects. Multi-spectral photoplethysmography (MS-PPG) biosensor intended for analysis of peripheral blood volume pulsations at different vascular depths has been designed and experimentally tested. Multi-spectral monitoring was performed by means of a three–wavelengths (405 nm, 660 nm and 780 nm) laser diode and a single photodiode with multi-channel signal output processing. The proposed methodology and potential clinical applications are …
Real-Time Photoplethysmography Imaging System
Real-time non-contact photoplethysmography imaging (PPGI) system for high-resolution blood perfusion mapping in human skin has been proposed. The PPGI system comprises of LED lamp, webcam and computer with video processing software. The purpose of this study is to evaluate the reliability of the PPGI system when measuring blood perfusion. The validation study of PPGI and laser-Doppler perfusion imager (LDPI) was performed during local warming of palm skin. Results showed that the amplitude of PPGI increases immediately after warming and well correlated with the mean LDPI amplitude (R=0.92+-0.03, p<0.0001). We found that PPGI technique has good potential for non-contact monitoring of blood p…
Audio-video atskaņotāju analīze un ātrdarbīga atskaņotāja izstrāde
Darbs veidots par mūsdienās aktuālu datorprogrammu – audio un video failu atskaņotāju – analīzi un jauna ātrdarbīga atskaņotāja izveidi. Tā galvenā būtība ir apskatīt ar to saistītās problēmas, tehnoloģijas un risinājumus. Īpaša uzmanība tiek pievērsta kvalitatīva atskaņotāja izveidei gan no lietošanas, gan tehniskiem aspektiem. Darba gaitā tiek apskatītas esošās atskaņošanas programmas, izpētīti un izvērtēti šo programmu plusi un mīnusi. Tiek nostādīti mērķi, kādi jāsasniedz izveidojamajam atskaņotājam, izvēlētas atbilstošās tehnoloģijas un sākta jaunā atskaņotāja praktiska izstrāde.
Multimodal imaging device for skin diagnostics: improvements and tests
In our work we have demonstrated our developed skin diagnostic imaging device and its hardware and software improvements. The device was tested in laboratory, to determine the stability of light uniformity and stability, as well as the performance of data processing. The improvements were focused to fulfill all requirements of doctors-dermatologists who use this device. Results showed that light field uniformity and stability were acceptable to get chromophore concentration maps of skin malformations.
Plaisu nevienmērīgā izvietojuma iespaids uz teorētiski aprēķinātajām elastības konstantēm ortogonāli stiegrotiem laminātiem
Darbā pētīti pret vidusplakni simetriski lamināti, kuriem iekšējo slāņu stiegrojums ortogonāls slogošanas virzienam, bet ārējo slāņu – paralēls. Analizēts plaisu nevienmērīgā izvietojuma iespaids uz efektīvajām elastības konstantēm. Eksperimentāli iegūta Junga moduļa un Puasona koeficienta atkarība no plaisu blīvuma transversajā slānī E- stikla šķiedras/ epoksīdsveķu laminātiem ar struktūrām [02/902]S, [0/902]S un[0/904]S, pakļaujot vienasīgai stiepes slogošanai. Pie iepriekš noteiktas deformācijas līmeņa slogošana pārtraukta un izmērīti faktiskie starpplaisu attālumi. Elastības raksturlielumu redukcija teorētiski noteikta, izmantojot divus plaisu sadalījuma veidus: bieži teorētiskos izvedu…
The analysis of blood flow changes under local anesthetic input using non-contact technique
In this work photoplethysmography imaging (PPGI) technique was used to obtain blood flow changes in human skin under regional anesthesia (RA). PPGI was evaluated from video taken by video camera for 26 patients 2 minutes before and immediately after RA, using custom developed software. Results showed that blood flow obtained by PPGI increases immediately after RA effect and the amplitude of PPGI showed correlation with temperature changes in human skin (r=0.8±0.14, p<0.0001). We found that PPGI technique can be usable for non-contact monitoring of quality of RA.
Reliability of automated optical determination of capillary refill time
The present study is devoted to assessment of automated optical capillary refill time determination by custom developed optoelectronic device prototype. Study comprised fifteen healthy volunteers; To induce capillary refill time changes the hand position challenge was utilized. During rest conditions slight inter-subject variation was observed: T90 (0.75±0.27 s), TSTB (2.20±0.58 s) and temperature at the measurement site (32.21±1.87 Co), however during hand position challenge results were more consistent. Rising hand substantially increased, while lowering slightly decreased capillary refill time. We conclude that automated determination of refill time have high clinical potential, however …