Three dimensional finite element simulation of polymer melting and flow in a single-screw extruder : optimization of screw channel geometry

Single-screw extrusion is one of the widely used processing methods in plastics industry, which was the third largest manufacturing industry in the United States in 2007 [5]. In order to optimize the single-screw extrusion process, tremendous efforts have been devoted for development of accurate models in the last fifty years, especially for polymer melting in screw extruders. This has led to a good qualitative understanding of the melting process; however, quantitative predictions of melting from various models often have a large error in comparison to the experimental data. Thus, even nowadays, process parameters and the geometry of the extruder channel for the single-screw extrusion are determined by trial and error. Since new polymers are developed frequently, finding the optimum parameters to extrude these polymers by trial and error is costly and time consuming. In order to reduce the time and experimental work required for optimizing the process parameters and the geometry of the extruder channel for a given polymer, the main goal of this research was to perform a coordinated experimental and numerical investigation of melting in screw extrusion. In this work, a full three-dimensional finite element simulation of the two-phase flow in the melting and metering zones of a single-screw extruder was performed by solving the conservation equations for mass, momentum, and energy. The only attempt for such a three-dimensional simulation of melting in screw extruder was more than twenty years back. However, that work had only a limited success because of the capability of computers and mathematical algorithms available at that time. The dramatic improvement of computational power and mathematical knowledge now make it possible to run full 3-D simulations of two-phase flow in single-screw extruders on a desktop PC. In order to verify the numerical predictions from the full 3-D simulations of two-phase flow in single-screw extruders, a detailed experimental study was performed. This experimental study included Maddock screw-freezing experiments, Screw Simulator experiments and material characterization experiments. Maddock screw-freezing experiments were performed in order to visualize the melting profile along the single-screw extruder channel with different screw geometry configurations. These melting profiles were compared with the simulation results. Screw Simulator experiments were performed to collect the shear stress and melting flux data for various polymers. Cone and plate viscometer experiments were performed to obtain the shear viscosity data which is needed in the simulations. An optimization code was developed to optimize two screw geometry parameters, namely, screw lead (pitch) and depth in the metering section of a single-screw extruder, such that the output rate of the extruder was maximized without exceeding the maximum temperature value specified at the exit of the extruder. This optimization code used a mesh partitioning technique in order to obtain the flow domain. The simulations in this flow domain was performed using the code developed to simulate the two-phase flow in single-screw extruders

TFRS kapsaminda sermayenin korunabilirliginin ekonomik kar analizi ve getirilen oneri uzerine bir uygulama

Globalization has removed borders of trade on the world and this result has directed to globalize the accounting systems. IAS (International Accounting Standards) and IFRS (International Financial Reporting Standards) are developed and updated everyday and these systems are integrated our country. “Capital Stock’s Conservation and Persistence” has been emphasized with importance on the IAS / IFRS’s "Conceptual Framework" and for that reason, the profit-loss calculations have been made with method of "Economic Profit and EBITDA (earnings before interest tax depreciation and amortization)" and the aim of this study is; giving a different standpoint for companies performance evaluations may be made more effective. Companies are to declare periodic amounts of profit or loss and as a result of this study is; these amounts have been found to reflect only tax or financial amounts. Hence, can be correctly calculated the real commercial amounts of profit-loss is demonstrating once more face the day importance of companies performance evaluation.peer-reviewe

Peroxidase-like activity of hemoglobin-based hybrid materials against different substrates and their enhanced application for H2O2 detection

ABSTRACT. Organic-inorganic hybrid nanoflowers method with unique properties are preferred than conventional immobilization methods for the past decade. Hereemoglobin-based hybrid material (HbNFs@Cu) was synthesized under different experimental conditions (pH 5.0-9.0 and 0.01-0.50 mgmL-1 of hemoglobin) obtaining a material size of 9-10 µm. The encapsulation percentage and weight yield of HbNFs@Cu were determined as 100% and 6.7%, respectively. The peroxidase-like activities of the material against different substrates (ABTS and Guaiacol) were compared to free hemoglobin. The HbNFs@Cu hybrid structure exhibited Vmax of 3.6995 EU/mg and a Michaelis-Menten constant (KM) of 0.1357 mM/mL. The HbNFs@Cu hybrid material was then used to catalyze the oxidation of a peroxidase substrate ABTS to the pigmented product, which provided a colorimetric and spectrophotometric detection of H2O2. The linear operating range, detectable colorimetrically as H2O2 sensor, is 0.005-0.0042 mM, while the linear operating range, detectable spectrometically, is 0.003-0.0042 mM. The limits of detection of colorimetric and spectrophotometric sensors were 0.005 mM and 0.003 mM, respectively. Collectively, these results showed that HbNFs@Cu can be used as colorimetric biosensor for H2O2 in potential applications such as pharmaceutical food, biomedical, environmental, and industrial.                     KEY WORDS: Hydrogen peroxide, Hemoglobin, Hybrid Material, Colorimetric assay   Bull. Chem. Soc. Ethiop. 2021, 35(3), 537-550.  DOI: https://dx.doi.org/10.4314/bcse.v35i3.

Impact of training giving to peadiatric nurses by interactive workshops against to problems during lactation period

Aim:  The study has been conducted in order to determine the impact of training which giving to peadiatric nurses by interactive workshops against to problems during lactation period.Methods:  This study, which is an experimental type in which pre-test/ post-test measurements were taken, was carried out in a state hospital in Samsun in October 2014. Before the training, the nurses accepted the presentation invitation. Evaluation of participants’ knowledge on the subject was performed via a Multiple Choice Questionnaire (MCQ) prepared by the researchers in relation with the literature. The study was conducted by 33 volunteer nurses working in the pediatric departments of a state hospital in the conference hall. MCQ, consisting of 24 questions, was answered by the participants before and after the interactive workshop. Analyses were performed using commercial software (IBM SPSS Statistics 20, SPSS Inc. An IBM Corp., Armonk, NY)Findings:  Nurses (n= 33) who work in pediatric units participated in the study. The  average age of nurses who participated to study is  36.30 ± 6.47 (min=21 max=48).  There was a significant improvement in mean test score after the lecture when compared with pre-lecture score (Mean =23.66, SD=0.54 vs. Mean=12.24, SD=4.11, z= -5.021 p = 0.000)Conclusions: Lecture based interactive workshop on the problems faced during lactation period helps to improve nurses’ knowledge. It also helps in overcoming deficiencies in nurses training

Babaların Sosyodemografik Özelliklerinin Eş Desteği ve Emzirme Başarısına Etkisi

Amaç: Bu çalışma babaların sosyodemografik özelliklerinin eş desteği ve emzirme başarısına etkisini değerlendirmek amacıyla planlanmıştır.Yöntem: Tanımlayıcı ve kesitsel yapılan araştırma, Mayıs - Kasım 2017 tarihleri arasın-da 0-24 ay bebeğe sahip özel bir bakım evinde çalışan veya çocuğu bu bakımevinde bakılan 78 baba çalışma kapsamına alınarak gerçekleştirildi. Gönüllü babalara yirmi sorudan oluşan anket formu dolduruldu. Verilerin değerlendirilmesinde yüzde, aritme-tik ortalama, frekans ve Ki-kare analizi kullanıldı.Bulgular: Yaşı 20-30 yıl, üniversite mezunu, kentsel bölgede yaşayan, tek çocuğa sahip, ekonomik durumu yüksek ve çekirdek aileye sahip olan babaların, gebelik kararını eşi ile birlikte alma, gebelik kontrollerine gitme, baba adayı eğitim programına katılma, eşi ile anne sütü ve yararları hakkında konuşma oranlarının istatistiksel olarak anlam-lı derecede daha yüksekdi (p<0.05). Eş desteği veren babaların çocuklarının tamamı sadece anne sütünü 6 ay aldığı ve eş desteği veren-vermeyen babaların çocuklarının toplam anne sütü alma süreleri arasında istatistiksel olarak anlamlı bir fark olduğu saptandı (p<0.05).Sonuç: Yaşı 20-30 yıl, üniversite mezunu, kentsel bölgede yaşayan, tek çocuğa sahip, ekonomik durumu yüksek ve çekirdek aileye sahip olan babaların eşlerini desteklediği, emzirmeye olumlu baktığı ve eş desteği alan annelerin emzirme başarılarının yüksek olduğu saptandı

ELISA Sisteminde Protein-İnorganik Hibrit Konjugatın Kullanılabilirliği

yokIn the Enzyme-linked immunosorbent assay method (ELISA), it is important to increase the immobilization efficiency of the functional molecules on the microplate and increase the signal-to-noise ratio in order to detect the target molecules with high sensitivity and selectivity. For this purpose, antibody functionalized materials can generate remarkable signal amplification with high enzyme capacity by using conventional immobilization methods. Recently, hybrid structures containing protein/enzyme and Cu3(PO4)2, which is a different enzyme immobilization method, have higher catalytic activity compared to the free form of protein-containing molecules as they have hierarchical microstructures and form large active surface areas. In this study; using protein-inorganic hybrid structure synthesis method, hybrid functionalized conjugate systems with enzyme, antibody and Cu3(PO4)2 were synthesized all together and characterization of the resulting structures was performed by SEM, EDX, XRD and FTIR analysis. When the findings obtained from the researches were evaluated, the hybrid nano structure showed 183.5 EU/mg peroxidase activity and free HRP enzyme showed 59.01 EU/mg activity. The performance of the ELISA system was measured using hybrid conjugate constructs prepared using various TNF-alpha specific antibodies at a -1 concentration of 5-1000 g mL . The performance of hybrid conjugate structure containing multiple organic molecules in ELISA system was higher than other structures. This method is a highly practical method that can replace enzyme-labeled antibody method in ELISA.yo

Kudret Narı (Momordica charantia Descourt.) Meyvesinden Saflaştırılan Peroksidaz Enzimi Kullanılarak Hibrit Nano Çiçekler Sentezlenmesi ve Direct Blue 1 Gideriminde Kullanılabilirlikleri

.Peroxidase enzymes are purified from different plant sources are used efficiently for the removal of dyes in industrial wastes. The fruit of bitter gourd (Momordica charantia), an inexpensive and easily accessible vegetable, is an important source of peroxidase. In this study, total protein content was found to be 0.485 mg/mL and peroxidase activity was found to be 2360.9 EU/mg as a result of 50% protein precipitation made from green bitter gourd. However; total protein amount was 0.232 mg/mL and free peroxidase activity was determined as 7719.30 EU/mg as a result of 60% protein precipitation made from ripe bitter gourd. Peroxidase enzymes which were purified from bitter gourd in different growth stages under optimum conditions showed higher enzymatic activity compared to free forms when immobilized via enzyme-inorganic hybrid nanoflower synthesis method. The highest peroxidase activity was seen in mature fruit and hybrid nanoflower form (19661, 6 EU/mg). In addition, the usability of hybrid nanoflowers was investigated compared to the free purified peroxidase for removal of Direct Blue 1 dye widely used in textile industry. It was determined that hybrid nanoflower form synthesized especially by using ripe bitter gourd peroxidase had more dye removal.

A new approach for green synthesis and characterization of Artemisia L. (Asteraceae) genotype extracts-Cu2 nanocomplexes (nanoflower) and their effective antimicrobial activity

.In this study, we have demonstrated the fabrication of novel organic-inorganic nanobio-antimicrobial agents called “nanoflowers” (NFs) and elucidate the increase in the antimicrobial activity of NFs. This is the first report that the NFs were formed of plant extracts as the organic components and copper (II) ions (Cu2+) as the inorganic component. The Artemisia L. (Asteraceae) methanol extracts from three genotypes including A. absinthium L. (Aa), A. vulgaris L. (Av) and A. ludoviciana Nutt. (Al) were selected in the NF synthesis. The effect of the plant extract concentrations on the morphology of NFs was examined. Most regular and uniform flower-shaped morpholo- gies were observed when a concentration of 0.1 mg mL-1 plant extract was used in the synthesis of NFs. The syntesized NFs were characterized with several techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), energy-dispersive X-ray (EDX) and X-ray diffraction analysis (XRD). The NFs exhibited much antimicrobial activity against the pathogens even at low concentrations compared to the extracts. The MICs and MBCs values for NFs were found to be range between 0.4 to 40 μg mL-1 and 40 to 400 μg mL-1 while those values for Aa, Av and Al extracts were ranged from 500-2000 μg mL-1 and 1000-4000 μg mL-1 for the studied pathogens, respectively.

BİR ÇİMENTO FABRİKASINDA DÖNER FIRIN PROSESİNİN ENERJİ ANALİZİ

Çimento fabrikaları, enerji sarfiyatı bakımından yüksek değerlere sahip sektörlerin başında yer almaktadır. Döner fırın ise, çimento fabrikalarında enerji tüketimi açısından önemli bir yere sahiptir. Dolayısıyla, tasarruf yöntemlerinin araştırılması ve uygulanabilirliği üzerine çalışmalar gün geçtikçe artmaktadır. Bu çalışmada klinker üretimi başına yaklaşık 75kW/ton enerji sarfiyatı olan bir fabrikanın döner fırın ünitesinin termodinamik analizi yapılmıştır. Bu maksatla işletme verileri göz önünde bulundurularak döner fırın ünitesine ait kütle ve enerji denklikleri oluşturulmuştur. Analizler sonucu ünitenin enerji verimi %58.6 olarak hesaplanmıştır. Yapılan analizler kayıpların fırın yüzeyinden, bacadan ve sızıntı havalardan kaynaklandığını göstermiştir. Bu sonuçlara bağlı olarak klinker üretiminde enerji verimliliğinin arttırılabilmesi için tavsiyelerde bulunulmuştur

Vaccination coverage and reasons for non-vaccination in a district of Istanbul

BACKGROUND: In order to control and eliminate the vaccine preventable diseases it is important to know the vaccination coverage and reasons for non-vaccination. The primary objective of this study was to determine the complete vaccination rate; the reasons for non-vaccination and the predictors that influence vaccination of children. The other objective was to determine coverage of measles vaccination of the Measles Immunization Days (MID) 2005 for children aged 9 month to 6 years in a region of Umraniye, Istanbul, Turkey. METHODS: A '30 × 7' cluster sampling design was used as the sampling method. Thirty streets were selected at random from study area. Survey data were collected by a questionnaire which was applied face to face to parents of 221 children. A Chi-square test and logistic regression was used for the statistical analyses. Content analysis method was used to evaluate the open-ended questions. RESULTS: The complete vaccination rate for study population was 84.5% and 3.2% of all children were totally non-vaccinated. The siblings of non-vaccinated children were also non-vaccinated. Reasons for non-vaccination were as follows: being in the village and couldn't reach to health care services; having no knowledge about vaccination; the father of child didn't allow vaccination; intercurrent illness of child during vaccination time; missed opportunities like not to shave off a vial for only one child. In logistic regression analysis, paternal and maternal levels of education and immigration time of both parents to Istanbul were found to influence whether children were completely vaccinated or non-vaccinated. Measles vaccination coverage during MID was 79.3%. CONCLUSION: Efforts to increase vaccination coverage should take reasons for non-vaccination into account