Usporedba ekonomskih i tehnoloških svojstava brezovine i bukovine za proizvodnju furnirske ploče

The aim of this study was to investigate the use of birch wood, one of the most important wood species used in the plywood industry, especially in Europe, the Nordic countries, Poland, Belarus and Russia as an alternative to beech wood. For this purpose, comparison was made of their economic and technological properties. In five-ply plywood manufacturing, beech (Fagus orientalis Lipsky) and birch (Betula pendula) veneer sheets were used with melamine urea formaldehyde (MUF) and urea formaldehyde (UF) resins. Some mechanical properties such as shear strength, bending strength and modulus of elasticity of plywood panels were conducted according to EN 314-1 and EN 310, respectively. Mean mechanical strength obtained for birch plywood panels was quite above the limit values specified in the related standards. When taking into consideration the annual increment of beech and birch trees in 1 ha and the time they need to reach suitable diameters for the manufacturing of rotary cut veneers, it was calculated that birch trees provide 2.46 times more physical harvesting than beech trees.U radu je istraživana uporaba brezovine kao jedne od najvažnijih vrsta drva koja se upotrebljava kao alternativa bukovini za proizvodnju furnirskih ploča, posebice u Europi, u nordijskim zemljama, Poljskoj, Bjelorusiji i Rusiji. Za potrebe rada uspoređivana su njihova ekonomska i tehnološka svojstva. U proizvodnji furnirske ploče od pet slojeva upotrijebljeni su listovi furnira od bukovine (Fagus orientalis Lipsky) i brezovine (Betula pendula), koji su slijepljeni ljepilom na bazi melamin-urea-formaldehidnih (MUF) i urea-formaldehidnih (UF) smola. Ispitana su mehanička svojstva furnirskih ploča prema normi EN 314-1 i EN 310, i to čvrstoća na smicanje, čvrstoća na savijanje i modul elastičnosti. Dobivene srednje vrijednosti čvrstoće brezovih i bukovih furnirskih ploča bile su znatno iznad graničnih vrijednosti navedenih u normama. Kada se u obzir uzme godišnji prirast bukve i breze na 1 ha šume i vrijeme potrebno za postizanje odgovarajućih promjera za proizvodnju ljuštenih furnira, izračunano je da breza osigurava 2,46 puta više raspoložive količine za sječu od bukve

Utjecaj parametara CNC obrade na kvalitetu površine drvnih ploča koje se upotrebljavaju u industriji namještaja

The processing of wood-based panels such as plywood, particleboard and fiberboard, which are widely used in the furniture industry, with CNC (Computer Numerical Control) milling machines has been increasing recently. Even though CNC milling machines have many advantages for furniture producers, it is difficult to set process parameters to obtain the desired surface quality of the material. Therefore, it is necessary to determine the most suitable of these parameters for the surface quality of each wood-based panel. This study aimed to determine the effects of processing parameters on the surface quality of plywood, particleboard and medium density fiberboard (MDF) panels processed in CNC milling machines. Furthermore, the average surface roughness values of these panels were compared after CNC processing. Three spindle rotational frequencies (10.000, 14.000 and 18.000 rpm), three feed rates (5, 7, and 9 m/min) and two cutting tool diameters (2 and 5 mm) were selected as CNC processing parameters. To determine the surface quality of wood-based panels, the surface roughness measurements were performed according to DIN 4768 standard and three surface roughness parameters (Ra, Rmax and Rz) were determined. According to the results of this study, it can be concluded that the surface roughness values of wood-based panels decreased with increasing spindle rotational frequency and feed rate, while they increased with increasing cutting tool diameter. Among the wood-based panels used in this study, the lowest average roughness values were obtained for plywood samples.Za obradu ploča na bazi drva kao što su furnirske ploče, iverice i vlaknatice, koje imaju široku primjenu u industriji namještaja, u posljednje se vrijeme sve češće primjenjuju CNC (Computer Numerical Control) glodalice. Iako CNC glodalice imaju mnoge prednosti za proizvođače namještaja, teško je odrediti parametre procesa za postizanje željene kvalitete površine obrađivanog materijala. Stoga je potrebno odrediti najprikladnije parametre obrade za svaku vrstu ploče na bazi drva. Cilj ovog istraživanja bio je utvrditi utjecaj parametara obrade CNC glodalicama na kvalitetu površine furnirske ploče, iverice i ploče vlaknatice srednje gustoće (MDF ploče). Nadalje, uspoređene su srednje vrijednosti hrapavosti površine tih ploča nakon CNC obrade. Kao parametri CNC obrade odabrane su tri frekvencije vrtnje vretena (10 000, 14 000 i 18 000 okr./min), tri posmične brzine (5, 7 i 9 m/min) te dva promjera reznog alata (2 i 5 mm). Za određivanje kvalitete površine ploča na bazi drva provedena su mjerenja hrapavosti površine prema normi DIN 4768, a hrapavost je iskazana trima parametrima hrapavosti površine (Ra, Rmax i Rz). Prema rezultatima ovog istraživanja može se zaključiti da su se vrijednosti hrapavosti površine ploča na bazi drva smanjivale s povećanjem frekvencije vrtnje vretena i posmične brzine, dok su se povećavale s povećanjem promjera reznog alata. Među pločama na bazi drva na kojima je provedeno ovo istraživanje najniže srednje vrijednosti hrapavosti dobivene su za uzorke furnirske ploče

Utjecaj materijala za oblaganje na svojstva posmičnog zida od furnirske ploče

Wooden buildings are intensely preferred especially in earthquake regions due to their many advantages such as lightness, durability, environmental friendliness, insulation and aesthetics. Shear walls provide the lateral resistance needed for light-frame wood structures to withstand earthquake loads. When sheathed with wooden structural panels such as plywood, shear walls can be strong, stiff, and ductile. This study focuses on the effects of production factors (wood species, thickness of panels) of plywood and fibre direction of sheathing material on the racking performance of the shear wall. The displacement at ultimate load decreased with increasing the thickness of plywood panels. It was also concluded that the black pine plywood panels were the best sheathing materials for the shear walls among wood species in terms of ductility. Scots pine plywood panels are the best sheathing materials for the shear walls among wood species in terms of load carrying capacity. Moreover, it was found that the wall formed perpendicular to fibre direction of sheathing materials could carry more load than the wall formed parallel to fibre direction.U potresnim su područjima osobito zastupljene drvene građevine zbog njihovih brojnih prednosti kao što su lakoća, trajnost, ekološka prihvatljivost, izolacija i estetika. Posmični zidovi osiguravaju bočnu otpornost kako bi lagane drvene konstrukcije izdržale potresna opterećenja. Kada su obloženi drvenim strukturnim pločama kao što je furnirska ploča, posmični zidovi mogu biti jaki, kruti i duktilni. Ovo je istraživanje fokusirano na učinke proizvodnih čimbenika furnirske ploče (vrstu drva, debljinu ploče) te na smjer vlakanaca materijala za oblaganje na svojstva posmičnog zida. Pokazalo se da se s povećanjem debljine furnirske ploče smanjuje pomak pri krajnjem opterećenju. Također je zaključeno da su sa stajališta duktilnosti furnirske ploče od drva crnog bora bolji izbor za oblaganje posmičnih zidova nego furnirske ploče od ostalih istraživanih vrsta drva. Sa stajališta nosivosti, za oblaganje posmičnih zidova najboljima su se pokazale furnirske ploče od drva bijelog bora. Osim toga, utvrđeno je da zid formiran okomito na smjer vlakanaca materijala za oblaganje može nositi veće opterećenje nego zid formiran paralelno sa smjerom vlakanaca materijala za oblaganje

Top and Bottom Squarks Decays under Cosmological Bounds

We investigate the fermionic decays of top squarks tilde t_{1,2} and bottom squarks tilde b_{1,2}$ in the Minimal Supersymmetric Standard Model with complex parameters M_1, mu, A_t and A_b . In the analysis we particularly take into account the cosmological bounds imposed by WMAP data. We plot the CP phase dependences of stop and sbottom decay widths.Comment: 1 text(9 pages)and 8 figures(6 pages). Total 15 pages. Accepted to be published in Phys.Lett.

Investigation of some surface properties and thermogravimetric analysis of veneer sheets treated with fire retardants

This study investigated the effects of different fire retardant chemicals on surface and thermal properties of veneer sheets. Beech (Fagus orientalis), alder (Alnus glutinosa), poplar (Populus deltoides) and scots pine (Pinus sylvestris) were chosen as wood species and zinc borate, borax, monoammonium phosphate and ammonium sulfate were chosen as fire retardant chemicals. The samples were impregnated by using the immersion method. Some surface properties such as colour measurements and surface roughness of the veneer sheets were conducted according to CIE L*a*b* system, DIN 4768 standard, respectively. Some thermal properties such as thermal conductivity of the veneer sheets were conducted according to ASTM C 518 & ISO 8301 and weight loss after combustion was determined by thermogravimetric analysis (TGA). According to the results from the study, it was found that fire retardant chemicals increased the thermal conductivity and surface roughness of veneer sheets. Also, TGA experiments showed that all of the fire retardant chemicals decreased the loss in weights

Predviđanje optimalne gustoće ekspandiranog polistirena za najbolje performanse toplinske izolacije polistirenske kompozitne iverice primjenom umjetne neuronske mreže

The objective of this study is to predict the optimum expanded polystyrene (EPS) densities for the best insulation properties of the particleboards manufactured with waste EPS instead of formaldehyde-based adhesives used in particleboard production with artificial neural network (ANN). For this purpose, the waste EPS particles of five different densities were used in the production of composite particleboards. The experimental dana used in the study were obtained from the previous study. Half of the beech, poplar, alder, pine and spruce chips were dried in a drying oven and the other half were naturally conditioned at room temperature, and then 18 mm thick three-layer composite particleboards were produced. The thermal conductivity of panels was determined according to ASTM C 518. The prediction model with the best performance and acceptable deviations was determined by using statistical and graphical comparisons between the experimental data and the prediction values obtained as a result of ANN analysis. Then, using this prediction model, the thermal conductivity coefficient values were estimated for the intermediate EPS densities that were not experimentally tested. According to the analysis findings, the thermal insulation performance for both beech and spruce polystyrene composite particleboards (PCP) panels increased with using of waste EPS foams with a density of 30 kg/m3. The lowest thermal conductivity values were obtained from the EPS waste foams with the density of 18, 13 and 22 kg/m3 for the PCP panels produced with poplar, alder and pine in the natural drying, respectively. In the technical drying, these values were found to be 15, 14 and 11-13 kg/m3, respectively. Technical drying showed much better thermal performance than natural drying while poplar indicated the best performance among the wood species.Cilj je ove studije primjenom umjetne neuronske mreže (ANN) predvidjeti optimalne gustoće ekspandiranog polistirena (EPS) radi postizanja najboljih izolacijskih svojstava iverice proizvedene s otpadnim EPS-om umjesto s ljepilom na bazi formaldehida, kakvo se rabi u proizvodnji iverice. Stoga je za proizvodnju iverice upotrijebljen otpadni EPS pet različitih gustoća. Eksperimentalni podatci primijenjeni u studiji dobiveni su prijašnjim istraživanjem. Jedna je polovica iverja bukovine, topolovine, johovine, borovine i smrekovine osušena u sušioniku, a druga je polovica iverja kondicionirana na sobnoj temperaturi. Od osušenoga i kondicioniranog iverja proizvedene su troslojne kompozitne iverice debljine 18 mm. Toplinska vodljivost ploča određena je metodom ASTM C 518. Predikcijski model najboljih svojstava i prihvatljivih devijacija određen je statističkom i grafičkom usporedbom eksperimentalnih podataka s vrijednostima predviđenima ANN analizom. Potom su primjenom predikcijskog modela procijenjeni koeficijenti toplinske vodljivosti za one gustoće ekspandiranog polistirena koje nisu eksperimentalno ispitane. Prema toj analizi, termoizolacijska svojstva polistirenske kompozitne iverice (PCP) od bukovine i smrekovine poboljšana su pjenom od otpadnog EPS-a gustoće 30 kg/m3. Najniže vrijednosti toplinske vodljivosti za polistirensku kompozitnu ivericu od prirodno osušene topolovine, johovine i borovine dobivene su uz uporabu pjene otpadnog ESP-a gustoće 18, 13 i 22 kg/m3. Za polistirensku kompozitnu ivericu od tehnički osušenog iverja te su vrijednosti bile 15, 14 i 11-13 kg/m3. Tehničkim sušenjem iverja postignuta su znatno bolja toplinska svojstva polistirenske kompozitne iverice nego prirodnim sušenjem, a topolovina je pokazala najbolja svojstva od svih ispitivanih vrsta drva

Comparison of thermal performances of plywood shear walls produced with different thermal insulation materials

Shear walls are one of the envelopes of light-frame wooden buildings where thermal insulation is most required. The thermal performance of shear walls can vary according to the type, properties and thickness of the wood and insulation materials used in their production. In this study, it was aimed to compare the thermal performances of plywood shear walls produced with different thermal insulation materials. For this aim, the archetype walls with properties similar to commonly used plywood shear walls were designed and produced for each thermal insulation material type and wood specie. The shear wall groups were formed by using Scots pine (Pinus sylvestris), black pine (Pinus nigra) and spruce (Picea orientalis) as wood species and cellulose, flax, felt, XPS, EPS, sheep’s, rock and glass wool as thermal insulation materials. Thermal conductivity of the shear wall groups was determined according to the ASTM C518-04 standard. Thermal resistance and other thermal performance parameters were calculated using the thermal conductivity values. As a result of the study, rock wool was the best thermal insulation material among the Scots pine shear wall groups while glass wool was the best thermal insulation material among the black pine and spruce shear wall groups. The shear walls produced with EPS foam boards indicated the worst thermal performance among all group

Oslobađanje formaldehida iz uslojene drvene ploče proizvedene od furnira obrađenih usporivačima gorenja i lijepljenih dvama tipovima urea-formaldehidnih ljepila

In the present study, it was aimed to investigate the formaldehyde release of plywood panels manufactured from beech, poplar, alder and scots pine veneers treated with 5 % aqueous solutions of commonly used fire retardants: zinc borate, boric acid, monoammonium phosphate and ammonium sulfate. Two types of urea formaldehyde (UF) resin with different free formaldehyde ratios (0.16 % and 0.20 %) in adhesive were used as adhesive. Formaldehyde release of plywood panels was determined according to fl ask method described in EN 717-3 standard. As a result of this study, it was found that formaldehyde release from panels produced by beech, poplar, alder and scots pine veneers treated with zinc borate and boric acid were higher than those of control panels, while lower formaldehyde release was obtained for panels treated with monoammonium phosphate and ammonium sulfate. This is valid for all four wood species. Treatment of monoammonium phosphate and ammonium sulfate caused considerable reduction in formaldehyde emission from manufactured plywood panels. In some usage areas, where high strength properties are not expected, plywood panels manufactured from veneers treated with monoammonium phosphate and ammonium sulfate may be used for reducing formaldehyde release.U radu je predstavljeno istraživanje oslobađanja formaldehida iz uslojenih drvenih ploča proizvedenih od furnira bukve, topole, johe i običnog bora tretiranih s 5 %-tnim vodenim otopinama najčešće upotrebljavanih usporivača gorenja: cinkova borata, borne kiseline, monoamonijeva fosfata i amonijeva sulfata. Za lijepljenje furnira upotrijebljene su dvije vrste urea-formaldehidnog ljepila (UF) različitog omjera slobodnih formaldehida (0,16 i 0,20 %) u njemu. Oslobađanje formaldehida iz uslojenih drvenih ploča određeno je perforatorskom metodom opisanom u standardu EN 717-3. Istraživanja su pokazala da je oslobađanje formaldehida iz uzoraka ploča proizvedenih od furnira bukve, topole, johe i običnog bora i tretiranih cinkovim boratom i bornom kiselinom veće nego iz kontrolnih uzoraka ploča, dok je za ploče tretirane monoamonijevim fosfatom i amonijevim sulfatom ustanovljena manja količina oslobođenog formaldehida. To vrijedi za sve četiri vrste drva. Tretiranje ploča monoamonijevim fosfatom i amonijevim sulfatom rezultirala je znatnim smanjenjem emisije formaldehida iz proizvedenih uslojenih drvenih ploča. Stoga se u nekim područjima uporabe u kojima se ne zahtijeva velika čvrstoća ploča mogu upotrebljavati ploče od uslojenog drva izrađene od furnira tretiranih monoamonijevim fosfatom i amonijevim sulfatom jer se iz njih oslobađaju manje količine formaldehida

Complications of arteriovenous fistula with polytetraflouroethylen grafts in hemodialysis patients

Purpose: Vessels with high venous flow rate are needed for the application of hemodialysis in patients needing chronic hemodialysis. The increase in the number of chronic hemodialysis patients has led to an increase in the number of vascular surgical operations. The aim of this study was to evaluate the results of polytetraflouroethylen (PTFE) graft arteriovenous fistula (AVF) applications.Materials and Methods: Files of 596 patients who received hemodialysis treatment at the Nephrology Unit of the Þanlýurfa Mehmet Akif Ýnan State Hospital between September 2009 and 2013 were retrospectively analyzed. PTFE grafts and autogenous AVFs applied in 22 patients were analyzed, and demographic data and PTFE graft associated complications of these patients were evaluated.Results: We found that the graft patency duration (months ± standard deviation) and the patency after graft revision were 16 ± 13 and 83.3%. Complications were detected in 14 patients (63%). One patient developed hematoma in early stages.Conclusions: We conclude that even if PFTE graft AVF applications cause significant complications, the procedure has a high patency rate after graft revision.Key words: Complication, polytetraflouroethylen graft, vascular acces

Analysis of Gait Dynamics of ALS Disease and Classification of Artificial Neural Networks

In this study, a gait device was used for gathering data. A group comprising control group and ALS patients was requested to walk using this device. Gait signals of the control group individuals and ALS patients taken from their left feet were recorded by means of the sensors sensitive to the force which was placed to the device. Spectral and statistical analyses of these signals were made. The results obtained from these analyses were used for making classification with Artificial Neural Network. In consequence of the classification, the individuals with ALS disease were diagnosed accurately with an average rate of 82 %. In the study, the signals taken from left foot of 14 normal individuals and 13 ALS patients were analyzed