Sinteza fenolne smole ojačane nanočesticama TiO2 i njezin utjecaj na gorivost lamelirane drvne građe (LVL)

In this study, phenol-formaldehyde (PF) resin has been modified with titanium dioxide nanoparticles (nano-TiO2) at a varying ratio from 0.05 wt.% to 1.5 wt.% to enhance the thermal properties and combustion performance of the resins. The effect of the nano-TiO2 modification on the properties (chemical or thermal) of the resins was determined by Fourier to transform infrared (FT-IR) and thermal analysis (TGA) techniques. In addition, the combustion performance of laminated veneer lumber (LVL) samples bonded with the PF resin modified with nano-TiO2 was tested. The result of the FT-IR analysis indicated that the modified PF resins had match peaks to the reference PF resin. These similarities of the peaks supported that the modified PF resins were successfully synthesise with phenol, formaldehyde, and nano-TiO2. The PF resins modified by nano-TiO2 demonstrated better thermal stability than the reference resin. The nano-TiO2 modified PF resin exhibited a favourable influence on the combustion characteristics of LVL. In consequence, PF resin modified with nano-TiO2 could be used as a combustion retardant adhesive in the wood industry.U ovom je istraživanju fenol-formaldehidna smola (PF) modificirana nanočesticama titanijeva dioksida (nano-TiO2) u različitim omjerima, od 0,05 tež.% do 1,5 tež.% kako bi se poboljšala njezina toplinska svojstva i svojstva gorivosti. Utjecaj modifikacije nanočesticama TiO2 na svojstva smola (kemijska i toplinska) određen je Fourierovom transformiranom infracrvenom spektroskopijom (FT-IR) i termogravimetrijskom analizom (TGA). Osim toga, ispitana je gorivost uzoraka lamelirane drvne građe (LVL) lijepljene PF smolom modificiranom nano-česticama TiO2. Rezultati FT-IR analize pokazali su da modificirane PF smole imaju jednake vrhove kao referentna PF smola. Te sličnosti vrhova potvrđuju da su modificirane PF smole uspješno sintetizirane s fenolom, formaldehidom i nanočesticama TiO2. PF smole modificirane nanočesticama TiO2 pokazale su bolju toplinsku stabilnost od referentne smole i povoljno su utjecale na gorivost LVL-a. Stoga zaključujemo da bi se PF smola modificirana nanočesticama TiO2 mogla upotrebljavati kao ljepilo za usporavanje gorenja u drvnoj industriji

Karakterizacija emisije formaldehida i svojstava gorenja ekoloških kompozitnih ploča za graditeljstvo proizvedenih na bazi ljusaka kikirikija (Arachis hypogaea)

The building sectors are increasingly in need of more wood-based panels. Forests and environments are being destroyed to produce these wood-based panels. The aim of this study is to protect forest assets by recycling peanut (Arachis hypogaea) husk and manufacturing particleboard for green building design. The manufactured composite panels were subjected to combustion and formaldehyde tests. According to the test results, peanut husk reduced the combustion time and increased the combustion temperature. Phenol-formaldehyde adhesive decreased illuminance values and the peanut husk ratio increased the illuminance values. It was understood that, when the peanut husk additive ratio increased, combustion times decreased. Slow-combustion of green building composite panels delays the danger of collapse in case of a fire in a building. The combustion performance of the composite panels can be improved by adding non-combustible materials that do not affect the adhesion performance of the composite panels. When the adhesive type is taken into consideration, it is seen that the FF additive ratio reduces the combustion time. According to the formaldehyde emission test results, 24 hours after the manufacturing process all composite panels met the requirements of the board formaldehyde class E1. These composite panels can be used in green buildings as a sustainable building material. The furniture industry can also use these agro-fiber composite panels as green materials.Građevni sektor ima sve veću potrebu za pločama na bazi drva za čiju se proizvodnju uništavaju šume i okoliš. Cilj ovog istraživanja bio je zaštititi šumska dobra recikliranjem ljusaka kikirikija (Arachis hypogaea) i proizvodnjom iverica namijenjenih zelenoj gradnji. Na tako proizvedenim kompozitnim pločama provedena su ispitivanja gorenja i emisije formaldehida. Rezultati su pokazali da se dodavanjem ljusaka kikirikija smanjuje vrijeme gorenja i povećava temperatura izgaranja ploča. Fenol-formaldehidno ljepilo pridonosi smanjenju vrijednosti osvjetljenja, a uz veći udio dodanih ljusaka kikirikija povećava se razina osvjetljenja pri gorenju. Pretpostavljeno je da će se s povećanjem udjela ljusaka kikirikija smanjiti vrijeme gorenja. Sporo gorenje kompozitnih ploča namijenjenih zelenoj gradnji odgađa opasnost od urušavanja u slučaju požara u zgradi. Svojstva gorenja kompozitnih ploča mogu se poboljšati dodavanjem nezapaljivih materijala koji ne utječu na adheziju kompozitnih ploča. S obzirom na vrstu ljepila, ustanovljeno je da se s povećanjem udjela FF ljepila skraćuje vrijeme gorenja. Prema rezultatima ispitivanja emisije formaldehida 24 sata nakon procesa proizvodnje, sve su kompozitne ploče zadovoljile klasu emisije formaldehida E1. Zaključeno je da se ispitivane kompozitne ploče u zelenoj gradnji mogu upotrebljavati kao održivi građevni materijal. Kao ekološki prihvatljive, te se kompozitne ploče na bazi agrovlakana mogu primjenjivati i u industriji namještaja

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Crime prediction model with spatial decision support systems: The case of theft crime in Ankara province

21. yüzyılın dinamik yapısında suç ile mücadele artan önemiyle tüm toplumun ilgi alanındadır. Çağın gereklilikleri ile kolluğun temel görevlerinin arasında suça müdahalenin yanında suçu önleme ve önceden doğru şekilde tahmin etme yer bulmuştur. Son 70 yıldır aktif olarak kullanılan suç haritalarına coğrafi bilgi sistemlerindeki (CBS) son gelişmelerle farklı yetenekler kazandırılmıştır. Bu sayede etkin suç analizleri yapılabilmekte, suç önleme taktik ve stratejileri geliştirilebilmektedir. Meydana gelen olayları tek bir pencerede görebilmeyi ve hızlı kararlar almayı kolaylaştıran suç bilgi sistemleri, suç analizleri ve suç tahminlemede etkin olarak kullanılmaktadır. Suçların konuma ve zamana dayalı tahmin yeteneği için geliştirilen Muhtemel Hotspot (PHotspot) Yöntemi, Muhtemel Kernel Yoğunluk Tahmini (PKDE) ile Zaman-Mekân Tarama İstatistiği (STSS) gibi yöntemlere ek olarak Mekânsal Karar Destek Sistemleri (MKDS) ile diğer bir suç tahmin ve analiz yöntemi olan Tekrar ve Yakın Tekrar (TYT) (Repeat and Near Repeat) Analizi ile de yakın çevreden etkin bir şekilde suç tahminlemesi yapılabilmektedir. Çalışmada, MKDS ve TYT yöntemleri birlikte kullanılmış, mesleki tecrübeler sonucunda belirlenen, suçun oluşumuna etki eden konum bazlı faktörlerin suçun tekrarlaması ile de dikkate alınabilecek miktarda ilişkili olduğu sonucuna ulaşılmıştır.In the dynamic structure of the 21st century, the fight against crime is in the interest of the whole society with its increasing importance. Among the requirements of the age and the basic duties of the law enforcement, preventing crime and predicting correctly beforehand, besides intervening in crime, took place. Crime maps, which have been actively used for the last 70 years, have gained different capabilities with the latest developments in geographic information systems (GIS). In this way, effective crime analyzes can be made and crime prevention tactics and strategies can be developed. Crime information systems, which make it easier to see the events in a single window and make quick decisions, are effectively used in crime analysis and crime prediction. In addition to methods such as Probable Hotspot (PHotspot) Method, Probable Kernel Density Estimation (PKDE) and Time-Space Scan Statistics (STSS) developed for location and time-based prediction capability of crimes, Spatial Decision Support Systems (SDSS) and other crime prediction and analysis with the Repeat and Near Repeat (RNR) Analysis method, an effective crime estimation can be made from the immediate environment. In the study, SDSS and RNR methods were used together, and it was concluded that the location-based factors affecting the formation of the crime, determined as a result of professional experience, are related to the repetition of the crime, which can be taken into account

The effects of some chemical materials on colour of tone for Elm wood Ulmus campestris Spach

Bu çalışmada, karaağaç (Ulmus campestris Spach.) odunundan hazırlanan deney örneklerine % 25' lik konsantrasyondaki NaOH + H2O2 (I. çözelti) ve NaSiO3 + H2O2 (II. çözelti) grupları ile renk açma işlemi yapılmıştır. Renk açma işleminden sonra poliüretan ve poliester vernik uygulanan yüzeylerde renk açıcı kimyasal maddelerin kırmızı renk tonu oluşumuna etkileri ASTM-D 2244 esaslarına uyularak belirlenmiştir. Sonuç olarak, kırmızı renk tonu en yüksek poliüretan vernik uygulanan naturel örneklerde (19.94), en düşük I. grup (NaOH + H2O2) çözelti ve poliester vernik uygulanan örneklerde (4.26) elde edilmiştir. Buna göre; düşük kırmızı renk tonu istenen işlemlerde renk açma işleminden sonra odun yüzeylere poliüretan vernik uygulanmamalıdır. Son katta poliüretan vernik uygulanması söz konusu olduğunda, şeffaf renksiz dolgu verniği kullanılması kırmızı renk tonu oluşumunu azaltabilir.In this study, it has been performed the bleaching process with NaOH + H2O2 and NaSiO3 + H2O2 which have 25 % concentration elm wood of red color of tone measuring. It has been carried out to measure the red color of tone according to the procedure of ASTM-D 2244 standards. It has been done the bleaching process for red colour of tone effects on the wood surface covered with polyurethane and polyester varnish of some chemical materials. As a result, it has been obtained the highest red color of tone as naturel samples with polyurethane varnish (19.94), the lowest red color of tone as I. solution (NaOH + H2O2) and polyester (4.26). According to this, polyurethane varnish must not be applied to have bleached surfaces that wishing the less red color of tone of surfaces after the bleching process. If the transparent filler varnish is used, the red color of tone can be reduced, in case of the polyurethane apply on the wood surfaces as a last layer

The effects of screw and back panels on the strength of corner joints in case furniture

WOS: 000251487900026This study was carried out to determine the effects of screw and back panel on the corner joints in case furniture produced from medium density fiber board MDF, and particle board (PB). For this purpose, the different test panels, the edges of which were covered or uncovered with solid wood or massive and back rebated, not back rebated samples, were used and the types of "L corner joints" were manufactured. Also, the plywood used for back panel had a thickness of 4 mm. Compression and tension strength tests were applied on the corner joints in accordance with ASTM-D 143-83 standards. As a result, the highest tension strength was obtained in covered edges of MDF as 181.7 Nm, the lowest in rebated and uncovered samples as 78.7 Nm, the highest compression strength was obtained in rebated and covered samples as 178.7 Nm, and the lowest was observed in unrebated and uncovered samples as 79.5 Nm. In conclusion, the edges of cupboard panels should be rebated and covered with solid wood or massive wood in Case furniture. (c) 2007 Elsevier Ltd. All rights reserved

The effect of the steam on weight and swelling rate of varnished waferboard (WFB)

Bu çalışmada, yüzeyleri sentetik vernikle kaplanmış 18 mm kalınlığındaki etiket yongalı levha (WFB) örnekleri 6, 24, 60 ve 96 saat süre ile su buharı etkisinde bırakılmıştır. Hazırlanan kontrol ve vernikli 10'ar adet örnek TS 3639 standardında belirlenen esaslara uygun olarak su buharı etkisi sonucu ağırlık, kalınlık ve genişlik değerlerinde meydana gelen değişmeler incelenmiştir. Kontrol örneklerine göre vernikli örnekler toplam 186 saat su buharı etkisinde bekletilmesi sonucu sırasıyla, ağırlık artışları % 14, kalınlık artışları % 7 ve genişlik artışları % 0,2 olarak tespit edilmiştir.In this study, the 18 mm thick experimental samples prepared from waferboard (WFB), covered all faces with synthetic varnish and control samples have been exposed to steam for 6, 24, 60 and 96 hour periods. The effects of weight, thickness and width values of the control and the varnished samples have been determined according to the procedure of the Turkish Standard (TS) 3639. As a result, according to the control samples different dimensional increases have been obtained on weight increases as %14 , thickness as %7 and width as % 0.2 respectively. According to these, there has been less change in the dimensions of the varnished samples than unvarnished one

EFFECTS OF EDGE COVERING ON TENSILE STRENGTH OF MDF

Dowels, 6, 8 and 10 mm ? diameters were bonded with PVAc adhesive on Medium Density Fiberboard (MDF). Edges were covered with 5, 8 and 12 mm beech wood materials, drilled 25 mm depth. Tensile strength measurments were made on the samples. The highest tensile strength value was given as 6 mm ? dowel and MDF covered with 8 mm thickness beech wood material (2.294 N/mm2), the lowest value was obtained with 10 mm ? dowel and with unprocessed MDF (1.314 N/mm2)