1,318 research outputs found
A Study on monitoring and optimisation of chromium uptake in tanning process
No full textBu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır. Yayınlanma izni olmayan tezlerin basılı kopyalarına Üniversite kütüphaneniz aracılığıyla (TÜBESS üzerinden) erişebilirsiniz.ÖZET TABAKLAMADA KROM TÜKETİMİNİN BİLGİSAYAR YARDIMI İLE İZLENMESİ VE OPTİMİZASYONU ÜZERİNE BİR ARAŞTIRMA MUTLU, Mehmet Mete Yüksek Lisans Tezi, Deri Teknolojisi Bölümü Tez Yöneticisi : Prof. Dr. Özcan SARI Ocak 1999, 114 sayfa Bu araştırmada; krom tüketiminin bilgisayar yardımıyla izlenmesi için deri örnekleri farklı sıcaklık ve bazifıkasyon zamanlan ile tabaklanmış ve tabaklama süresince flottede krom konsantrasyonu kısa zaman aralıkları ile spektrofotometrede ölçülerek banyodaki krom tüketimi bilgisayar grafikleri ile izlenmiştir. Grafiklerden elde edilen bilgiler ve mamul deri örneklerine uygulanan fiziksel test ve kimyasal analiz sonuçlan karşılaştınlarak krom tüketiminin optimal koşullan tesbit edilmeye çalışılmıştır. Anahtar sözcükler : Proses kontrol, krom tabaklama, krom tüketimiVII ABSTRACT A STUDY ON MONITORING AND OPTIMISATION OF CHROMIUM UPTAKE IN TANNING PROCESS MUTLU, Mehmet Mete MSc in Leather Technology Supervisor : Prof. Dr. Özcan SARI January 1999, 114 pages In this research, for computer aided monitoring of chromium exhaustion, leather samples have been tanned with various application times of temperature and basification and chromium exhaustion of the float has been monitored by computer graphics by measuring the chromium concentration of the float with a spectrophotometer in short time intervals. Optimal conditions of chromium tannage have been tried to be determined by comparing the datas obtained from graphics and results of the physical tests and chemical analysis applied to the leather samples.. Keywords : Process control, chrome tanning, chrome exhaustio
The substituent effects on the structure and surface morphology of polyaniline
No full textWOS: 000274114000061In this work, poly(2-fluoroaniline), poly(2-chloroaniline), poly(2-methylaniline), and poly(N-ethylaniline) were prepared by a self-assembly method using an oxidizing system consisting of a dopant anion, p-toluene sulfonate with ammonium peroxydisulfate. The effects of substituents on the surface morphology, conductivity, molecular weight, spectral and thermal properties of the polymers were studied. SEM results revealed that the surface morphology of the resulting polymers changed from nanofiber to spherical structure by changing the substituents on the aniline monomers. The structure and properties of these conducting films were characterized by FTIR, UV-vis, elemental analysis, TGA, conductivity, and cyclic voltammetry. The polymer films show electroactivity in monomer free solution. Molecular weight of the polymers was determined by gel permeation chromatography. The dry electrical conductivity values of the substituted-polyanilines were found to be lower than that of PANI. The results revealed that the molecular structures of the polymers were similar to those of the emeraldine form of polyanilineAnadolu University Research Found [031064]Contract grant sponsor: Anadolu University Research Found; contract grant number: 031064
Ion chromatography-potentiometric detection of inorganic anions and cations using polypyrrole and overoxidized polypyrrole electrode
No full textWOS: 000258011000002Polypyrrole (PPy) and overoxidized polypyrrole (OPPy) films were used as a potentiometric detector in ion chromatography, in order to determine some anions and cations in water samples. Electrodeposition of PPy film was performed by constant potential at +0.80V (vs. Ag/AgCl) in an aqueous solution containing 0.1 M pyrrole and 0.2 M sodium nitrate. The overoxidation of PPy film was carried out in 0.1 M NaOH solution by cycling the potential between +0.80 and +1.20V at 50mV s(-1). The PPy film exhibited good sensitivity toward, especially, fluoride and chloride ions. The lowest detection limit (3 sigma) observed was 10(-8) M for fluoride with PPy detector. This is the first study using OPPy electrode for the potentiometric detection of both monovalent and divalent cations in literature. The correlation coefficients obtained from the calibration curves were 0.947-0.991 for anions and 0.998-0.999 for cations. The response of ions at the PPy and OPPy electrodes maintained over 90-94% of the original value for 45 and 30 days, respectively. It can be concluded from the observed data that these electrodes can be used as an alternative detector materials to analyse anions and cations in the water samples by ion chromatograph
Energetska varnost v času krize: študiji primera Bolgarije in Srbije
No full textThis thesis aims to assess the EU’s external energy policy and to what degree it has been embraced by small states during the energy crisis by posing the question, “How does European Union membership influence the external energy policy decisions of small states within the foreign policy dimension during energy security crises?”. To answer this, the research is taking Bulgaria and Serbia as case studies due to their similar population sizes, GDP, and energy consumptions. This research conceptualizes energy security and energy diplomacy to understand how diplomacy and energy dependencies are interrelated and how this relationship can be utilised as a tool in international relations. Through supporting the qualitative work on foreign policy analysis with the quantitative analysis of the energy industry structures and energy dependencies of Serbia and Bulgaria in a comparative manner, this research is conducting mixed research on the issue. The comparison of Bulgaria and Serbia enables the author to analyse and understand the role of EU membership
Repair of silorane composite - using the same substrate or a methacrylate-based composite?
No full textOBJECTIVE: The study aimed to analyze the shear bond strength of aged silorane composite repaired with the same substrate or a conventional methacrylate-based composite after different mechanical and adhesive surface treatments. METHODS: Silorane composite specimens were aged by thermal cycling (5000 cycles, 5-55°C) and randomly assigned to different surface treatments (each group n=16): diamond bur abrasion, aluminum oxide sandblasting, silica coating, or hydrofluoric acid etching. Then, an adhesive system corresponding to the repair composite or a combination of silane agent and the respective adhesive was applied. Silorane composite or a nanofiller composite were adhered onto the conditioned surfaces. In the control group (n=16), silorane composite was adhered to fresh substrate (incremental build up). After further thermal cycling, shear bond strength was tested and failure modes were assessed. Data were analyzed by ANOVA/post hoc tests, Weibull statistics and Chi(2)-test (p≤0.05). RESULTS: Incremental shear bond strength (control group: 21.0±10.5MPa) was achieved by all groups except those etched with hydrofluoric acid or samples abraded with diamond bur and repaired with the nanofiller composite without silane application. Generally, the application of the silane agent improved repair bond strength of the nanofiller but not of the silorane composite. Cohesive failure was observed more frequently than adhesive failure when the silane agent was applied or when silorane composite was used for repair. SIGNIFICANCE: Silorane composite can be repaired with either the same substrate or a methacrylate-based nanofiller composite but requires mechanical surface treatment and - in case of the methacrylate-based composite - silanization prior to adhesive application
Adsorption of Nitrate Ions onto Sepiolite and Surfactant-Modified Sepiolite
No full textThe adsorption of nitrate ions onto clay minerals has not been given much attention, possibly because clay surfaces are negatively charged. In order to increase the positive charge on the surface, sepiolite was modified in the present studies by treatment with dodecylethyldimethylammonium (DEDMA) bromide. After such modification, it was found that the maximum amount of nitrate ion adsorbed occurred at a pH value of 2.0. The chemical composition of natural sepiolite was determined by EDX methods and surface characterization of both natural and modified sepiolite samples was undertaken using FT-IR spectroscopic techniques. The adsorption of nitrate ions onto these adsorbents was determined by ion chromatography. The kinetic parameters of the adsorption process were calculated and it was shown that the reaction kinetic data could be fitted using the pseudo-second-order rate model. The calculated results indicate that both natural and surfactant-modified sepiolite are effective sorbents for the removal of anionic contaminants; however, the surfactant-modified sepiolite (453 mmol/kg) was more effective than the unmodified sepiolite (408 mmol/kg) in this respect. The adsorption data obtained were well described by the Freundlich adsorption isotherm
The effect of scanning the palate and scan body position on the accuracy of complete‐arch implant scans
No full textÖzcan, Mutlu/0000-0002-9623-6098; Cakmak, Gulce/0000-0003-1751-9207; Yilmaz, Burak/0000-0002-7101-363XBackgroundWhether stitching the palate during intraoral digital scans of implants would improve, scanning accuracy is unclear. PurposeEvaluate the effect of stitching the palate and the scan body position on the trueness (distance and angular deviation) and precision of digital scans in a completely edentulous situation. Materials and MethodsAn edentulous maxillary model with four parallel dental implant analogs was fabricated and intraoral scan bodies were attached. The entire surface was scanned using an industrial scanner to generate a master reference model digital scan (MRM-DS). Digital scans of the master model were made using an intraoral scanner and the resulting scans were divided into two groups [stitched palate (S) and unstitched palate (U)]. All test scans were converted to STL files and superimposed over the MRM-DS. ResultsFor trueness, scan body position had a significant effect on distance (P<.001) and angular (P<.001) deviation values. In terms of precision, no significant difference was found in distance (P = .051) and angular deviations (P = .36) between stitched and unstitched techniques. ConclusionsThe accuracy and precision of digital scans of edentulous maxillary arch was similar independent of stitching or unstitching the palate. Position of the implant had a significant effect on trueness
Repair of Bulk-Fill and Nanohybrid Resin Composites: Effect of Surface Conditioning, Adhesive Promoters, and Long-Term Aging.
Full text linkThe aim of the study was to investigate the effect of different repair procedures on the repair bond strength of bulk-fill and nanohybrid resin composites after different aging periods. The resin composite blocks (8 × 8 × 4 mm3) were prepared from a bulk-fill (reliaFIL Bulk) and a nanohybrid (reliaFIL LC) resin composite and grouped according to aging duration (6 months, 1 year, and 2 years). Following aging, the blocks were assigned to different surface treatments; air-abrasion with aluminum oxide powder, roughening with a diamond bur, and no treatment. After cleansing with phosphoric acid, a silane layer (Porcelain Primer) was applied on the surface of half of the specimens in each group. The specimens were subdivided into two groups (n = 5): Scotchbond Universal (3M Oral Care) and All-Bond Universal (Bisco). The blocks were repaired with the nanohybrid composite (8 × 8 × 8 mm 3). The repaired specimens were stored in distilled water (37 °C/24 h) and segmented into beams. Half of the beams were immediately subjected to microtensile μTBS testing (1 mm/min), while the other half was stored in distilled water (37 °C) for 6 months before testing. Failure modes were analyzed using stereomicroscope and SEM. Statistical analyses were performed with ANOVA and least significant difference tests (LSD) tests (p = 0.05). The extension of aging periods (6 months, 1 year, and 2 years) reduced the repair bond strength in some groups for both resin composites (p < 0.05). The air-abrasion and bur roughening improved the repair bond strength (p < 0.05). The silane application did not influence the repair bond strength and durability (p > 0.05). There was no difference among the universal adhesives in the same surface treatment groups (p > 0.05). The mechanical roughening treatments are necessary for the repair of resin composite. The universal adhesives might be used for the repair of resin composites regardless of silane content without prior silane application
Color Change after 25% Hydrogen Peroxide Bleaching with Photoactivation: A Methodological Assessment Using Spectrophotometer versus Digital Photographs
Full text linkThis study aimed to evaluate the color change of teeth bleached with light activation using two different objective color measurement approaches after two years of clinical follow-up. A cross-sectional retrospective clinical study according to STROBE was followed including 30 participants. The 25% hydrogen peroxide gel (Philips Zoom) was applied with a supplementary LED light for 15 min in four cycles. Tooth color was assessed based on CIEL*a*b* values using a spectrophotometer (Spectroshade) at different time points (baseline, post bleaching, 1 week, 1 year, and 2 years). Standardized digital photographs were taken at each time point. The L*, a*, and b* values were measured from the digital photographs using Adobe Photoshop software. The color difference (ΔE) was separately calculated using the L*, a*, and b* values obtained with spectrophotometric and photographic analyses at each evaluation time. Data were analyzed with non-parametric tests (p < 0.05). A color regression was detected by both measurement approaches after 1 and 2 years (p < 0.05). Greater ΔE values were acquired with the spectrophotometer compared to the digital photographic analysis (p < 0.05). Although a greater color change was observed with the spectrophotometer, both approaches were able to detect the color rebound using the 25% hydrogen peroxide light-activated in-office system. Digital photographic analysis might therefore be used to assess color change after bleaching
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