13 research outputs found
On a decomposition of partitioned J-unitary matrices
We propose a new decomposition of hyperbolic block-unitary matrices into a product of a hyperbolic block-rotation and a block-diagonal hyperbolic unitary matrix. A similar result is known in the real space equipped with the Euclidean scalar product, but we generalize it to the complex spaces equipped with hyperbolic scalar products.
We shall also present an example how such a decomposition might be used to calculate other decompositions with block-operations
LiveGraphics3D
U ovom Älanku predstavljamo Java applet za interaktivni prikaz trodimenzionalnih objekata izraÄenih u programskom sustavu Mathematica. Autor appleta je Martin Kraus s TehniÄkog sveuÄiliÅ”ta u MĆ¼nchenu, a applet je ukljuÄen u on-line inaÄicu Mathematice, webMathematicu. Sam applet slobodno je dostupan i možete se njime koristiti da biste postavili interaktivne trodimenzionalne objekte na vlastite web stranice. U Älanku objaÅ”njavamo kako se to radi, a za Äitatelje koji se ne žele upuÅ”tati u izradu web stranica pokazujemo kako postaviti trodimenzionalne objekte na forumu math.e
MatriÄna funkcija predznaka
Dobro poznate funkcije (poput funkcije predznaka, korijena i logaritma) ponekad se, osim na brojevima, primjenjuju i na matricama. U Älanku dajemo definicije takvih funkcija, te promatramo njihova osnovna svojstva. Zatim se bavimo matriÄnom funkcijom predznaka, koja je relativno jednostavna, ali i dovoljno složena da na njoj pokažemo kako se s takvim funkcijama radi. Na kraju opisujemo dva algoritma za raÄunanje vrijednosti opisane funkcije koje zainteresirani Äitatelj može prilagoditi i za raÄunanje druge funkcije
Surgical treatment of chronic pilonidal sinus
KroniÄni pilonidalni sinus steÄena je bolest kože, nastala kao posljedica kroniÄne upalne bolesti zahvaÄenog dijela kože, koja stvara cistu s epiteliziranim potkožnim kanalima. Bolest veÄinom pogaÄa mlaÄe muÅ”karce. PoviÅ”en BMI i sjedilaÄki naÄin života smatraju se vodeÄim Äimbenicima rizika. Cilj je istraživanja bila usporedba vremena cijeljenja, uÄestalosti seroma, infekcije i dehiscencije rane te prosjeÄnog trajanja bolniÄkog boravka kod pacijenata operiranih prvi put zbog kroniÄnoga pilonidalnog sinusa u Klinici za kirurgiju SveuÄiliÅ”ne kliniÄke bolnice Mostar, u razdoblju od 1. lipnja 2015. do 1. lipnja 2017. godine, s praÄenjem recidiva jednu godinu nakon kirurÅ”kog zahvata. Pacijenti su podijeljeni u tri skupine prema vrsti zahvata: ekscizija s primarnim zatvaranjem (23,0%), ekscizija sa sekundarnim cijeljenjem (55,2%) te ekscizija sa zatvaranjem Limbergovim režnjem (21,8%). Odabir metode uÄinjen je na osnovi procjene i iskustva operatera. VeÄina pacijenata ukljuÄenih u istraživanje imala je poviÅ”en BMI (72,4%). Pacijenti operirani ekscizijom uz primarno zatvaranje i Limbergovim rotacijskim režnjem imali su kraÄe vrijeme cijeljenja nego pacijenti s ekscizijom uz sekundarno cijeljenje. UÄestalost seroma bila je najveÄa kod pacijenata s ekscizijom uz primarno zatvaranje (70,6%), dok je najmanja bila u pacijenata s Limbergovim rotacijskim režnjem (29,4%). ProsjeÄno vrijeme boravka u bolnici bilo je 6,4 dana (min. = 3, maks. = 13;
SD = 1,919). Razlike u vremenu boravka u bolnici s obzirom na vrstu kirurÅ”kog zahvata nisu se pokazale statistiÄki znaÄajnima. Kod pacijenata s Limbergovim rotacijskim režnjem zabilježena su 2 (10,5%) recidiva u jednogodiÅ”njem razdoblju nakon kirurÅ”kog zahvata. Skupina pacijenata s primarnim zatvaranjem u tom je razdoblju imala 7 (35%) recidiva, a ona sa sekundarnim cijeljenjem 6 (12,5%) recidiva. Razlika u broju recidiva izmeÄu skupina pacijenata lijeÄenih Limbergovim rotacijskim režnjem, primarnim zatvaranjem ili sekundarnim cijeljenjemb na granici je statistiÄke znaÄajnosti (p = 0,55). Zatvaranje defekta Limbergovim rotacijskim režnjem smanjuje broj poslijeoperacijskih komplikacija i skraÄuje cijeljenje, Å”to olakÅ”ava poslijeoperacijski oporavak pacijenta.Chronic pilonidal sinus is an acquired skin disease resulting from chronic inflammation of an affected skin area. It creates a cyst with epithelized subcutaneous channels. The disease mostly affects younger men with
elevated BMI and sedentary lifestyle being the main risk factors. The aim of this study was to compare wound healing times, seroma, wound infection and wound dehiscence frequency, average length of hospital stay and recurrence rate in patients undergoing first-time operation for chronic pilonidal sinus at the Surgery clinic of University hospital Mostar from June 2015 to June 2017, with recurrence rate monitoring for one one year after the operative procedure. The patients were divided into three groups by the type of operating procedure: excision with primary closure (23.0%), excision with healing by secondary intention (55.2%) and excision with Limberg flap closure (21.8%). Most of the patients included in this study had elevated BMI (72.4%). Patients who were operated using primary closure and Limberg flap closure had on average shorter wound healing times than patients operated with excision and secondary intention healing. Seroma frequency was highest in patients operated using primary closure (70.6%) and lowest in patients operated using Limberg flap closure (29.4%). Average length of hospital stay was 6.4 days (min 3, max 13; SD 1.919). There were no statistically significant differences in hospital stay between different types of operating procedures used. Patients operated using Limberg flap closure had two (10.5%) cases of recurrence in the one year period after the operation. There were seven (35.0%) recurrences of the disease in patients operated using primary closure and six (12.5%) recurrences in patients operated using healing with secondary intention. The difference in the number of recurrences between patients operated using primary closure, healing by secondary intention and Limberg flap closure was borderline statistically significant. We find that Limberg flap closure reduces postoperative complications and wound healing time which improves postoperative recovery
The hyperbolic Schur decomposition (extended)
We propose a hyperbolic counterpart of the Schur decomposition, with the emphasis on the preservation of structures related to some given hyperbolic scalar product. We give results regarding the existence of such a decomposition and research the properties of its block triangular factor for various structured matrices
The hyperbolic Schur decomposition
We propose a hyperbolic counterpart of the Schur decomposition, with the emphasis on the preservation of structures related to some given hyperbolic scalar product. We give results regarding the existence of such a decomposition and research the properties of its block triangular factor for various structured matrices