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Ahmed, Sheikh Ali
Publikationer (10 of 14) Visa alla publikationer
Elustondo, D., Ahmed, S. A. & Oliveira, L. (2014). Drying Western Red Cedar with Superheated Steam (ed.). Drying Technology, 32(5), 550-556
Öppna denna publikation i ny flik eller fönster >>Drying Western Red Cedar with Superheated Steam
2014 (Engelska)Ingår i: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, nr 5, s. 550-556Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

This exploratory study evaluated the possibility of drying 50-mm-thick western red cedar with superheated steam. Since there are no industrial facilities in Canada drying western red cedar with superheated steam, the study was designed to explore the potential of this technology in terms of lumber quality, moisture content distribution, and drying time. The experiments showed that the 50-mm-thick product can be dried in less than three days without jeopardizing lumber quality (in comparison with the two weeks that is currently required in conventional kilns), and the percentage of pieces that remained wet after drying was within the 10% to 15% range that is typically tolerated in industry.

Nyckelord
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-12313 (URN)10.1080/07373937.2013.843190 (DOI)000333995000007 ()2-s2.0-84896084731 (Scopus ID)b6cea034-bc05-4402-a836-5700bd1d9609 (Lokalt ID)b6cea034-bc05-4402-a836-5700bd1d9609 (Arkivnummer)b6cea034-bc05-4402-a836-5700bd1d9609 (OAI)
Anmärkning

Validerad; 2014; 20140319 (andbra)

Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-07-10Bibliografiskt granskad
Sehlstedt-Persson, M. & Ahmed, S. A. (2014). Metodutveckling för mögeltestning av trä - förstudie: TCN Slutrapport (ed.). Paper presented at . : TräCentrum Norr
Öppna denna publikation i ny flik eller fönster >>Metodutveckling för mögeltestning av trä - förstudie: TCN Slutrapport
2014 (Svenska)Rapport (Övrigt vetenskapligt)
Abstract [sv]

Syftet med denna förstudie har varit att utveckla enkla och robusta forcerade mögeltester på trä som kan följas och utvärderas kontinuerligt i forskningsprojekt som bedrivs inom beständighetsområdet vid LTU och SP Trätek i Skellefteå. Testerna som gjorts i klimatskåp bygger på naturlig kontaminering och klimatval som gynnar mögeltillväxt.De metoder som utvecklats gör inte anspråk på att kunna erbjuda jämförelser med andra etablerade metoder utan enbart jämförelser inom batcher som ingår i de material- och processvariabler som studeras, exempelvis inom virkestorkning, värmebehandling och impregneringsmetoder.I förstudien utvärderades ett antal olika klimatval i ett klimatskåp som användes i försöken. Mögelpåväxt gynnas av stabil och hög RF, mörker och stillastående luft. Därför täcktes glasdörren till skåpet med svart plast och övre delen av klimatskåpet skärmades av med en mellanplåt eftersom en fläkt cirkulerar luften i kammaren nedre delar. I den övre delen av klimatskåpet gjordes noggranna mätningar av klimatet för att säkerställa ett jämnt och stabilt klimat i olika positioner.Mögelkontaminerat furumaterial sparat från tidigare TCN projekt användes som ”smittokälla” genom att placeras i klimatskåpets nedre del vid valt klimat under 2 dygn för att infektera kammaren med mögelsporer. Därefter placerades försöksmaterialet i klimatskåpets övre del. Smittokällan dvs. det kontaminerade materialet befann sig i skåpet under hela försöket. Inspektion av mögelpåväxtengjordes regelbundet fram tills beslut togs att avbryta försöket och utvärdera mögelpåväxten. Den utvärderingsmetod som används för att bedöma mögelpåväxt bygger på en visuell bedömningsskala översatt i ”praktisk användning” som utarbetats i tidigare TCN-projekt.Den lämpligaste metoden bedöms vara att använda klimatskåpets ”set-points” +27°C/95 % RF samt att avbryta försöket efter ca 12-14 dagar. Mögelgraderna på de undersökta proverna har då varit av samma omfattning som efter ca 100 dagars forcerat utomhustest beskrivit i tidigare TCN-projekt.Den framtagna metoden har använts i fyra ”skarpa” studier som publicerats i vetenskapliga tidskrifter. Detta får ses som att projektet varit lyckat och utgör ett viktigt vetenskapligt bidrag.Metoden beskrivs i detalj i en av dessa publikationer som finns som bilaga till denna rapport nämligen: “Development of a new rapid method for mould testing in a climate chamber: Preliminary tests.” Ahmed, S. A., Sehlstedt-Persson, M. &Morén, T. jul 2013 i :Holz als Roh- und Werkstoff .71 ,4 ,s. 451-461.11 s.Den framtagna metoden har fungerat mycket bra. Metoden har följande fördelar:* Den är enkel, robust och billig.* Mögelpåväxten kan följas på plats.* Det är möjligt att få svar redan efter två veckor på inverkan av olika variabler som undersöks.* Enkel kontaminering – ingen uppodling av speciella mögelarter.* Upp till 44 stycken prover kan ingå i en batch, beroende av dimension.Metoden har följande nackdelar:* Ingen standardiserad metod dvs. det är inte möjligt göra jämförelser mellan olika försöksomgångar utan endast möjligt att göra ”inom-batch” jämförelser.* Ingen kontroll av vilka mögelarter som angriper virket.

Ort, förlag, år, upplaga, sidor
TräCentrum Norr, 2014. s. 23
Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-23988 (URN)936c3e03-abcd-4975-8e22-2e316e28ecde (Lokalt ID)936c3e03-abcd-4975-8e22-2e316e28ecde (Arkivnummer)936c3e03-abcd-4975-8e22-2e316e28ecde (OAI)
Anmärkning
Godkänd; 2014; 20140303 (marseh)Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2017-11-24Bibliografiskt granskad
Sidorova, E., Ahmed, S. A. & Elustondo, D. (2014). Wood thermal-modification at Luleå University of Technology (ed.). In: (Ed.), Mojgan Vaziri; Dick Sandberg (Ed.), Final Cost Action FP0904 Conference: “Recent Advances in the Field of TH and THM Wood Treatment” : May 19-21, 2014, Skellefteå, Sweden : book of abstracts. Paper presented at Cost action FP0904 Conference : 19/05/2014 - 21/05/2014 (pp. 75). Skellefteå: Luleå tekniska universitet
Öppna denna publikation i ny flik eller fönster >>Wood thermal-modification at Luleå University of Technology
2014 (Engelska)Ingår i: Final Cost Action FP0904 Conference: “Recent Advances in the Field of TH and THM Wood Treatment” : May 19-21, 2014, Skellefteå, Sweden : book of abstracts / [ed] Mojgan Vaziri; Dick Sandberg, Skellefteå: Luleå tekniska universitet, 2014, s. 75-Konferensbidrag, Meeting abstract (Refereegranskat)
Ort, förlag, år, upplaga, sidor
Skellefteå: Luleå tekniska universitet, 2014
Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-34446 (URN)8a6e542b-410f-4e6d-a991-e0d967f28ae6 (Lokalt ID)9789174399378 (ISBN)9789174399387 (ISBN)8a6e542b-410f-4e6d-a991-e0d967f28ae6 (Arkivnummer)8a6e542b-410f-4e6d-a991-e0d967f28ae6 (OAI)
Konferens
Cost action FP0904 Conference : 19/05/2014 - 21/05/2014
Anmärkning
Godkänd; 2014; 20140516 (andbra)Tillgänglig från: 2016-09-30 Skapad: 2016-09-30 Senast uppdaterad: 2017-11-25Bibliografiskt granskad
Ahmed, S. A., Yang, Q., Sehlstedt-Persson, M. & Morén, T. (2013). Accelerated mold test on dried pine sapwood boards: Impact of contact heat treatment (ed.). Paper presented at . Journal of wood chemistry and technology, 33(3), 174-187
Öppna denna publikation i ny flik eller fönster >>Accelerated mold test on dried pine sapwood boards: Impact of contact heat treatment
2013 (Engelska)Ingår i: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, nr 3, s. 174-187Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We test the hypothesis that the combination of kiln drying of double-stacked boards and contact heat treatment will reduce the susceptibility of treated boards to colonization by mold fungi. Winter-felled Scots pine (Pinus sylvestris L.) sapwood boards were double-stacked in an industrial kiln in ‘‘sapwood out’’ and ‘‘sapwood in’’ positions. Dried samples were then contact heat-treated using a hot press at three different temperatures (140°C, 170°C, and 200°C) for three different periods (1, 3, and 10 min). Accelerated mold test was performed in a climate chamber where naturally mold infected samples were used as a source of mold inocula. Contact heat treatment degraded the saccharides which accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth was 170°C for 10 min. But, for industrial application, the most feasible combination of temperature and time would be 200°C for 3 min. We concluded that double stacking/contact heat treatment used is an environmentally friendly alternative to chemicals for reducing mold on Scots pine sapwood boards.

Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-15844 (URN)10.1080/02773813.2013.773041 (DOI)000317716000002 ()2-s2.0-84876728788 (Scopus ID)f674f798-5b6a-4559-8fb7-e49ce44b09d5 (Lokalt ID)f674f798-5b6a-4559-8fb7-e49ce44b09d5 (Arkivnummer)f674f798-5b6a-4559-8fb7-e49ce44b09d5 (OAI)
Anmärkning
Validerad; 2013; 20130129 (sheahm)Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-07-10Bibliografiskt granskad
Ahmed, S. A., Morén, T., Hagman, O., Cloutier, A., Fang, C.-H. & Elustondo, D. (2013). Anatomical properties and process parameters affecting blister/blow formation in densified European aspen and downy birch sapwood boards by thermo-hygro-mechanical compression (ed.). Paper presented at . Journal of Materials Science, 48(24), 8571-8579
Öppna denna publikation i ny flik eller fönster >>Anatomical properties and process parameters affecting blister/blow formation in densified European aspen and downy birch sapwood boards by thermo-hygro-mechanical compression
Visa övriga...
2013 (Engelska)Ingår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, nr 24, s. 8571-8579Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Approximately, 13.5 % of the standing volume of productive forest land in Sweden is covered by birch and aspen, which provides the vast potential to produce value-added products such as densified wood. This study shows whether it is possible to densify those species with a thermo-hygro-mechanical (THM) process using heat, steam, and pressure. In this process, transverse compression on thin European aspen (Populus tremula) and downy birch (Betula pubescens) boards was performed at 200 ºC with a maximum steam pressure of 550 kPa. To obtain a theoretical 50 % compression set, the press’s maximum hydraulic pressure ranged from 1.5 to 7.3 MPa. Preliminary tests showed that ~75 % of the birch boards produced defects (blisters/blows) while only 25 % of the aspen boards did. Mainly, radial delamination associated with internal checks in intrawall and transwall fractures caused small cracks (termed blisters) while blows are characterized by relatively larger areas of delamination visible as a bumpy surface on the panel. Anatomical investigations revealed that birch was more prone to those defects than aspen. However, those defects could be minimized by increasing the pre-treatment time during the THM processing.

Nationell ämneskategori
Biomaterial Annan maskinteknik
Forskningsämne
Träfysik; Träproduktutveckling
Identifikatorer
urn:nbn:se:ltu:diva-7066 (URN)10.1007/s10853-013-7679-9 (DOI)000324111700028 ()2-s2.0-84891903228 (Scopus ID)5618af53-b6b8-496d-a902-97c101649a98 (Lokalt ID)5618af53-b6b8-496d-a902-97c101649a98 (Arkivnummer)5618af53-b6b8-496d-a902-97c101649a98 (OAI)
Anmärkning
Validerad; 2013; 20130823 (sheahm)Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-07-10Bibliografiskt granskad
Ahmed, S. A., Sehlstedt-Persson, M. & Morén, T. (2013). Development of a new rapid method for mould testing in a climate chamber: Preliminary tests (ed.). Paper presented at . European Journal of Wood and Wood Products, 71(4), 451-461
Öppna denna publikation i ny flik eller fönster >>Development of a new rapid method for mould testing in a climate chamber: Preliminary tests
2013 (Engelska)Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, nr 4, s. 451-461Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12-14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.

Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-8083 (URN)10.1007/s00107-013-0697-0 (DOI)000320376800006 ()2-s2.0-84879217007 (Scopus ID)685a5886-bee5-4256-9062-40b0ed78c195 (Lokalt ID)685a5886-bee5-4256-9062-40b0ed78c195 (Arkivnummer)685a5886-bee5-4256-9062-40b0ed78c195 (OAI)
Anmärkning
Validerad; 2013; 20130423 (sheahm)Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-07-10Bibliografiskt granskad
Yang, Q., Karlsson, O., Ahmed, S. A. & Morén, T. (2013). Dimensional stability and water repellency of european aspen improved by oxidized carbohydrates (ed.). Paper presented at . BioResources, 8(1), 487-498
Öppna denna publikation i ny flik eller fönster >>Dimensional stability and water repellency of european aspen improved by oxidized carbohydrates
2013 (Engelska)Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, nr 1, s. 487-498Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Small samples from European aspen (Populus tremula L.) were impregnated with carbohydrates oxidized by Fenton’s reagent using water in a vacuum, followed by heating in an oven at 103°C. An antiswelling efficiency (ASE) of around 45% for wood treated with oxidized glucose and 35% for wood treated with oxidized sucrose was obtained. Samples treated with oxidized carbohydrates gave water repellent effectiveness (WRE) values over 35%. The decrease in cell wall thickness during impregnation was about 18% less in the presence of oxidized glucose than samples only treated with Fenton’s reagent. An ASE of 20% for the wood samples that had been treated with oxidized glucose was obtained after 7 days of soaking in water. The reasons for the improvement in dimensional stability are discussed in this work.

Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-9532 (URN)82f3919a-d280-4cb6-8abd-f69eb96bc438 (Lokalt ID)82f3919a-d280-4cb6-8abd-f69eb96bc438 (Arkivnummer)82f3919a-d280-4cb6-8abd-f69eb96bc438 (OAI)
Anmärkning
Validerad; 2013; 20130129 (sheahm)Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2017-11-24Bibliografiskt granskad
Ahmed, S. A., Hansson, L. & Morén, T. (2013). Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood (ed.). Wood Science and Technology, 47(3), 499-513
Öppna denna publikation i ny flik eller fönster >>Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood
2013 (Engelska)Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 47, nr 3, s. 499-513Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Studying the impregnation and distribution of oil-based preservative in dried wood is complicated as wood is a nonhomogeneous, hygroscopic and porous material, and especially of anisotropic nature. However, this study is important since it has influence on the durability of wood. To enhance the durability of thermally modified wood, a new method for preservative impregnation is introduced, avoiding the need for external pressure or vacuum. This article presents a study on preservative distribution in thermally treated Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) sapwood using computed tomography scanning, light microscopy, and scanning electron microscopy. Secondary treatment of thermally modified wood was performed on a laboratory scale by impregnation with two types of preservatives, viz. Elit Träskydd (Beckers) and pine tar (tar), to evaluate their distribution in the wood cells. Preservative solutions were impregnated in the wood using a simple and effective method. Samples were preheated to 170°C in a drying oven and immediately submerged in preservative solutions for simultaneous impregnation and cooling. Tar penetration was found higher than Beckers, and their distribution decreased with increasing sample length. Owing to some anatomical properties, uptake of preservatives was low in spruce. Besides, dry-induced interstitial spaces, which are proven important flow paths for seasoned wood, were not observed in this species.

Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-10629 (URN)10.1007/s00226-012-0509-4 (DOI)000318292900005 ()2-s2.0-84877828892 (Scopus ID)9759fb33-caeb-4495-80d5-0bcb79063304 (Lokalt ID)9759fb33-caeb-4495-80d5-0bcb79063304 (Arkivnummer)9759fb33-caeb-4495-80d5-0bcb79063304 (OAI)
Anmärkning

Validerad; 2013; 20121009 (sheahm)

Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-12-14Bibliografiskt granskad
Ahmed, S. A., Sehlstedt-Persson, M., Hansson, L. & Morén, T. (2013). Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy (ed.). Journal of Wood Science, 59(1), 57-66
Öppna denna publikation i ny flik eller fönster >>Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy
2013 (Engelska)Ingår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 59, nr 1, s. 57-66Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The aim of this experiment was to impregnate thermally modified wood using an easy and cost-effective method. Industrially processed thermally modified European aspen (Populus tremula L.) and birch (Betula pubescens Ehrh.) were collected and secondarily treated at the laboratory scale with the preservatives tung oil, pine tar and Elit Träskydd (Beckers) using a simple and effective method. Preservative uptake and distribution in sample boards were evaluated using computed tomography (CT) and scanning electron microscopy (SEM) techniques. Preservative uptake and treatability in terms of void volume filled were found the highest in Beckers and the lowest in tung oil-treated samples. Thermally modified samples had lower treatability than their counterpart control samples. More structural changes after thermal modification, especially in birch, significantly reduced the preservative uptake and distribution. The differences of preservatives uptake near the end grain were high and then decreased near the mid position of the samples length as compared with similar type of wood sample. Non-destructive evaluation by CT scanning provided a very useful method to locate the preservative gradients throughout the sample length. SEM analysis enabled the visualization of the preservative deposits in wood cells at the microstructural level.

Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-7179 (URN)10.1007/s10086-012-1299-x (DOI)000315037000008 ()2-s2.0-84874105544 (Scopus ID)5807e96a-4097-4c82-9f68-31f9f6386aee (Lokalt ID)5807e96a-4097-4c82-9f68-31f9f6386aee (Arkivnummer)5807e96a-4097-4c82-9f68-31f9f6386aee (OAI)
Anmärkning

Validerad; 2013; 20121022 (sheahm)

Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-12-14Bibliografiskt granskad
Ahmed, S. A., Sehlstedt-Persson, M. & Morén, T. (2013). Mould susceptibility of Scots pine (Pinus sylvestris L.) sapwood: Impact of drying, thermal modification, and copper-based preservative (ed.). Paper presented at . International Biodeterioration & Biodegradation, 85, 284-288
Öppna denna publikation i ny flik eller fönster >>Mould susceptibility of Scots pine (Pinus sylvestris L.) sapwood: Impact of drying, thermal modification, and copper-based preservative
2013 (Engelska)Ingår i: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 85, s. 284-288Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The development of mould on wood surfaces depends on several factors. Although mould does not affect the mechanical properties of wood, it greatly reduces the aesthetic value of wood like the sapwood of Scots pine (Pinus sylvestris L.), which is very prone to mould. In addition, adverse health effects of mould on humans are also a great concern. Different types of dried and treated wood were used to observe whether they had enhanced durability against mould following an accelerated laboratory test method in a climate chamber. Samples were green, air-dried, industrially thermally-modified, treated with copper-based preservative, and kiln-dried wood, which were tested within a single test run. The test produced the following main results: the thermal modification increased the durability of the wood, and the protective effectiveness of alternative treatments was comparable to that of commercially available copper-based treatment. However, the initial moisture content of the samples during mould exposure had a great influence on the onset of mould growth. The risk of mould susceptibility of industrial kiln-dried lumber can be reduced by drying using the double-layering technique which likely forced the nutrients to deposit near the evaporation surfaces followed by planing off the nutrient enriched edges.

Nationell ämneskategori
Biomaterial
Forskningsämne
Träfysik
Identifikatorer
urn:nbn:se:ltu:diva-12380 (URN)10.1016/j.ibiod.2013.06.031 (DOI)000327166300039 ()2-s2.0-84884246330 (Scopus ID)b84bb295-5eee-4f48-babb-1a3ab3acb148 (Lokalt ID)b84bb295-5eee-4f48-babb-1a3ab3acb148 (Arkivnummer)b84bb295-5eee-4f48-babb-1a3ab3acb148 (OAI)
Anmärkning
Validerad; 2013; 20130607 (sheahm)Tillgänglig från: 2016-09-29 Skapad: 2016-09-29 Senast uppdaterad: 2018-07-10Bibliografiskt granskad
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