Values Of Tan Research Articles

Giant Spin Transfer Torque in Atomically Thin Magnetic Bilayers*Supported by the Research Grants Council of Hong Kong (Grant Nos. HKU17303518 and C7036-17W), and the University of Hong Kong (Seed Funding for Strategic Interdisciplinary Research).

In cavity quantum electrodynamics, the multiple reflections of a photon between two mirrors defining a cavity is exploited to enhance the light-coupling of an intra-cavity atom. We show that this paradigm for enhancing the interaction of a flying particle with a localized object can be generalized to spintronics based on van der Waals 2D magnets. Upon tunneling through a magnetic bilayer, we find that the spin transfer torques per electron incidence can become orders of magnitude larger than ℏ/2, made possible by electron’s multi-reflection path through the ferromagnetic monolayers as an intermediate of their angular momentum transfer. Over a broad energy range around the tunneling resonances, the damping-like spin transfer torque per electron tunneling features a universal value of (ℏ/2)tan (θ/2), depending only on the angle θ between the magnetizations. These findings expand the scope of magnetization manipulations for high-performance and high-density storage based on van der Waals magnets.

Temperature-dependent dielectric loss in BaTiO3: Competition between tunnelling probability and electron-phonon interaction

The temperature-dependent impedance spectroscopy, optical absorption spectroscopy, and Raman spectroscopic measurements have been carried out on BaTiO3 in the temperature range from 350 K to 430 K in order to understand the possible correlation between dielectric loss measured in terms of loss tangent (tan(δ)), band gap (Eg) and electron-phonon coupling parameter (λe-ph). It has been observed that in the tetragonal phase tan(δ) increases marginally, whereas in cubic phase tan(δ) shows a decreasing trend with increasing temperature. It has been observed that λe-ph increases with temperature and shows a sudden increase by almost two-fold at tetragonal to cubic transition temperature. The marginal increase in the value of tan(δ) with temperature in tetragonal phase is understood by considering the competition between the tunnelling of electron from valence to the conduction band and electron-phonon coupling, whereas; decrease in the value of tan(δ) in the cubic phase as a function of temperature may be due to the dominating contribution of electron-phonon coupling. Present investigations clearly establish the strong correlation between the temperature dependence of dielectric loss, the value of band gap, and electron-phonon interaction.

Synthesis and characterization of aluminum citrate compounds and evaluation of their influence on the formation of hydrogels based on polyacrylamide

Aluminum citrate is used as a conformance control agent to improve oil production and excess water production. This paper discusses the formation of mono and polynuclear aluminum species from the synthesis of aluminum citrate and evaluates these compounds as crosslinkers in hydrogels for conformance control. The products obtained from the synthesis were characterized by Fourier-transform infrared spectrometry (FTIR), elemental analysis (CHN), scanning electron microscopy (SEM), and inductively coupled plasma–optical emission spectrometry (ICP-OES). The FTIR analyses indicated the presence of mononuclear aluminum citrate complexes at pH 3 and polynuclear species starting at pH 4. These results were corroborated by CHN and ICP-OES techniques, which revealed the variation of carbon, oxygen, hydrogen, and alumina precipitate levels as functions of pH variation. The focus of the study was to assess how these crosslinking agents perform in hydrogel formation under reservoir conditions. Rheological analysis showed that the values of tan (delta) of the hydrogel synthesized with aluminum citrate at pH 6 were lower than 0.1, indicating strong gels, while at pH 9, the values were above 0.1, indicating weak gels. These results are in agreement with those obtained by FTIR, which showed that at pH 6, the structures of the aluminum citrate complex were probably in the form [Al3(C6H5O7)3(OH)4(H2O)]4−. This structure appears to allow easier access to the aluminum orbital for the crosslinking process compared to the gel composed of aluminum citrate synthesized at pH 9 [Al3(C6H6O7)3(OH)4(H2O)5]4−.

Attenuation properties of epoxy‐Ta2O5 and epoxy‐Ta2O5‐Bi2O3 composites at γ‐ray energies 59.54 and 662 keV

AbstractEpoxy resin filled with suitable high Z elements can be a potential shield for X‐rays and γ‐rays. In this work, we present the γ‐ray attenuation properties of epoxy composites filled with (0–30 wt%) Tantalum pentoxide (Ta2O5) and Ta2O5‐Bi2O3, which were prepared by open mold cast technique. X‐ray diffraction patterns showed crystalline peaks of Ta2O5 and bismuth oxide (Bi2O3) in the prepared epoxy‐Ta2O5 and epoxy‐Ta2O5‐Bi2O3 composites. Homogeneity of the samples at higher filler wt% was revealed by SEM images. Mechanical characterization showed the enhanced mechanical strength of epoxy‐Ta2O5‐Bi2O3 composites compared to epoxy‐Ta2O5. Higher storage modulus and glass transition temperature of the epoxy‐Ta2O5‐Bi2O3 composites showed enhanced stiffness and thermal stability when compared to neat and epoxy‐Ta2O5. Decrease in the value of tan(δ) at higher content of filler loadings indicated the good adhesion between filler and matrix. Mass attenuation coefficients of epoxy‐Ta2O5 (30 wt%) composites at γ‐ray energies 59.54 and 662 keV were found to be 0.876 cm2 g–1 and 0.084 cm2 g–1, while that of epoxy‐Ta2O5‐Bi2O3 (30 wt% Bi2O3) composite were 1.271 cm2 g–1 and 0.088 cm2 g–1, respectively. The epoxy‐5% Ta2O5‐30% Bi2O3 composites with higher μ/ρ value and tensile strength may be a potential γ‐ray shield in various radiation environments.

Immigrant song: nostalgic tensions in Shaun Tan’s The Arrival

ABSTRACT Shaun Tan’s The Arrival is the surreal wordless tale of a migrant coming to a new and unfamiliar land. It is a graphic novel drawn in sepia tones, that displays a fantastic universe full of imaginary animals, retro-futuristic machineries, and a ubiquitous, unintelligible language. Comments on the work, which enjoyed a large critical and commercial success, notably praised the nostalgic allure of its richly detailed pencil drawings, the author’s vivid imagination and the self-proclaimed ‘universal’ appeal of the tale recounted. This essay uses The Arrival as a case study to investigate how graphic novels can achieve a nostalgic effect, not only through the use of thematic elements, but also thanks to structural and stylistic features. It does so by examining the relation between nostalgia and migration; then, through an investigation of the style, structure and motifs exhibited by Tan’s text, it discusses the strategies it adopts to prompt in its reader a nostalgic reaction; it explores its sense of pastness; it reflects on the symbolic value of Tan’s visual imaginary, full of intertextual references mostly orbiting around the migration theme; finally, it questions the purported universality of Tan’s story.

Investigation on space charge dynamics and mechanical properties of Epoxy Alumina nanocomposites

Epoxy nanocomposites with different wt% of alumina was prepared by use of high-speed shear mixer and high-frequency sonicator process, and the electrical and mechanical properties of the materials were investigated. Surface potential variation and trap distribution analysis were carried out with epoxy nanocomposites. Space charge analysis was carried out through Pulsed Electro Acoustic (PEA) technique. The dielectric constant and tan (δ) values of epoxy alumina nanocomposites were measured at different frequencies and temperatures. Contact angle and corona inception voltage caused by a water droplet showed a direct correlation. The viscoelastic properties of the epoxy nanocomposite material were examined through DMA studies. It was concluded that an increase in the supply frequency increases the storage modulus and loss modulus of the epoxy alumina nanocomposites. Glass transition temperature and activation energy increase with an increase in wt% of alumina content in epoxy resin. LIBS analysis indicates that the plasma temperature calculated increases with an increase in the wt% of alumina content in epoxy resin. Also, the measured plasma temperature and hardness of the material showed a direct correlation.

Effect of Hybrid Reinforcement on the Mechanical Properties of Vinyl Ester Green Composites

The present article highlights the development of hybrid-fiber-reinforced composites using a vacuum-assisted resin transfer molding technique on low-cost flax fibers, carbon fiber, glass fibers and a vinyl ester resin system. Flax fibers are introduced to modulate mechanical properties, green credentials, cost, and the weight of carbon/glass/vinyl ester composites. The hybridization effect of flax, carbon, and glass fibers on mechanical properties, including tensile and flexural strengths, flexural modulus, impact strength, interlaminar shear strength, and damping is evaluated, which is also observed by SEM. The dynamic mechanical analysis was carried out for the composites with a three-point bending mode within a frequency range of 0 to 100 Hz. The results of the experiment reveal that hybrid composites with flax fabric and glass fabric had the highest flexural strength (727.8 MPa) and impact strength (0.171 J/mm2) compared with other composites. The dynamic mechanical analysis also showed that the highest value of Tan δ (0.0722) and damping ratio (2.75 %) were obtained compared with those of other composites.

Crop response of greenhouse soil-grown cucumber to total available N in a Nitrate Vulnerable Zone

Abstract Intensive vegetable production in soil is commonly associated with low N use efficiency (NUE) and consequently appreciable N losses that have negative environmental impacts. Improved N management practices for intensive vegetable crops require detailed knowledge of crop response to N supply. This study evaluated the effects of increasing total available N (TAN, i.e. the sum of soil mineral N at planting, N mineralized from organic matter, and mineral fertilizer N applied by fertigation) on cucumber grown in soil in a greenhouse. Parameters assessed were: yield, dry matter production (DMP), crop N uptake, nitrogen use efficiency (NUE) and potential NO3− leaching loss. The study was conducted in three growing seasons, in autumn, spring and late spring. Three commercial cultivars were examined, in the Late Spring crop, to assess possible cultivar differences. Five N treatments were applied, in the Autumn and Spring crops, as different N concentrations in nutrient solution that were applied in all irrigations throughout the crops. The applied N concentrations were N1: 0.7–1.0 mmol L-1, N2: 4.7–5.7 mmol L-1, N3: 12.1–13.8 mmol L-1, N4: 16.3–17.6 mmol L-1 and N5: 19.7–21.1 mmol L-1. The cultivar ´Strategos´ was used in both crops. Three N treatments (N1: 2.4 mmol L-1; N2: 8.5 mmol L-1and N3: 14.8 mmol L-1) were continuously applied throughout the Late Spring crop to three different cultivars (´Strategos´, ´Padrera´, and ´Mitre´). Total and marketable yield, relative to maximum value, and DMP were strongly related to TAN in linear-plateau relationships for the three growing seasons and three cultivars. Using relationships that include data from the three cropping seasons and the three cultivars, TAN values for maximum DMP, total yield, and marketable yield were 222 ± 15 kg ha−1, 221 ± 14 kg ha−1 and 228 ± 15 kg ha−1, respectively, for the Autumn, Spring and Late Spring crops. The relationships of crop N uptake to TAN, and DMP to crop N uptake, were described by a logarithmic equation. The relationship of N uptake efficiency to TAN (i.e. N uptake/TAN) was described by an exponential decay equation. Considering all crops and cultivars, these relationships were described by individual equations with R2 values of 0.75-0.96. The consistency of these relationships indicate that there are general responses of greenhouse-grown cucumber to N, which is not affected by growing season or cultivar. Measured NO3− leaching losses were low because of good irrigation management. Residual mineral N was considered to be indicative of the potential NO3− leaching loss; residual soil mineral N increased exponentially with TAN, being 196 and 330 kg N ha−1 for the highest N treatments in the Autumn and Spring crops, respectively. The information provided by this study will enable the total N supply (TAN) to be matched to cucumber crop N requirements thereby reducing excessive N supply and consequent negative environmental impacts.

Electricity production from gelatin wastewater using single-chamber microbial fuel cells

The purpose of this study was to determine the performance of electricity production from gelatin wastewater in a single chamber microbial fuel cells (MFCs). The treatment of MFCs using effective microorganisms (EM4) with concentration 0% (F0), 1.25% (F1), 2.5% (F2), and 5% (F3). Experimental results showed the voltage, current, and resistance in F1 were better than to other treatments. The best treatment of BOD (20.91±0.95 mg/L) and COD (81.64±0.01 mg/L) values with concentration 1.25% EM4 (F1). The higher concentration of EM4 has given lower of TAN values (3.24±0.01 mg/L for F0, 1.69±0.39 mg/L for F1, 0.73±0.44 mg/L for F2, and 0.24±0.11 mg/L for F3). The pH values were not significantly different in all treatment (7.36±0,02 for F0, 7.34±0.02 for F1, 7.55±0.01 for F2, and 7.11±0.01 for F3). The temperature of all the treatment were 25.8°C. The best performance of electricity production was the treatment with concentration 1.25% EM4 (F1) because in all parameters give the best results, except resistance.

Proposal and assessment of an aquaculture recirculation system for trout fed with harvested rainwater

A sustainable aquaculture production involves alternatives, as recirculating aquaculture systems (RAS), in order to increase the water supply efficiency. This paper aims: a) to propose a method for dimensioning a RAS filled and additionally supplied with water from a rainwater harvesting systems (RHS) and; b) to evaluate the efficiency of the system based on the supply of rainwater from the RHS, the quality of water in the RAS, and the development of aquatic organisms. A pilot aquaculture farm for rainbow trout (Oncorhynchus mykiss) production was designed and dimensioned. On one hand, the RAS with a configuration based on a treatment tower provided acceptable values of pH, TAN, and alkalinity. The temperature was slightly above the recommended temperature but did not negatively impact trout development. On the other hand, the water use efficiency reached 178 L/kg of fish, instead of 210,000 L/kg in an open flow system for trout rearing. The RHS fulfilled the additional required water on the test period of the pilot farm and is expected to supply at least 92% on average during the useful life. Regarding the aquatic organisms’ development, the system allowed both a better Length/ weight ratio and a lesser mortality rate compared to previous studies of RAS. In contrast to other studies in the literature, the mathematical models for dimensioning the system were calculated as a function of the final biomass expected in the tank instead of the quantity of supplied feed. Therefore, this method confirmed the applicability of this alternative criterion for designing biofilters and aquaculture systems.

Optimal subsets in the stability regions of multistep methods

In this work, we study the stability regions of linear multistep or multiderivative multistep methods for initial value problems by using techniques that are straightforward to implement in modern computer algebra systems. In many applications, one is interested in (i) checking whether a given subset of the complex plane (e.g., a sector, disk, or parabola) is included in the stability region of the numerical method, (ii) finding the largest subset of a certain shape contained in the stability region of a given method, or (iii) finding the numerical method in a parametric family of multistep methods whose stability region contains the largest subset of a given shape. First, we describe a simple procedure to exactly calculate the stability angle α in the definition of A(α)-stability by representing the root locus curve of the multistep method as an implicit algebraic curve. As an illustration, we consider two finite families of implicit multistep methods. We exactly compute the stability angles for the k-step BDF methods (3 ≤ k ≤ 6) and discover that the values of tan(α) are surprisingly simple algebraic numbers of degree 2, 2, 4, and 2, respectively. In contrast, the corresponding values of tan(α) for the k-step second-derivative multistep methods of Enright (3 ≤ k ≤ 7) are much more complicated; the smallest algebraic degree here is 22. Next, we determine the exact value of the stability radius in the BDF family for each 3 ≤ k ≤ 6, that is, the radius of the largest disk in the left half of the complex plane, symmetric with respect to the real axis, touching the imaginary axis and lying in the stability region of the corresponding method. These radii turn out to be algebraic numbers of degree 2, 3, 5, and 5, respectively. Finally, we demonstrate how some Schur–Cohn-type theorems of recursive nature and not relying on the root locus curve method can be used to exactly solve some optimization problems within infinite parametric families of multistep methods. As an example, we choose a two-parameter family of implicit-explicit (IMEX) methods: we identify the unique method having the largest stability angle in the family, then we find the unique method in the same family whose stability region contains the largest parabola.

Biofilm Density on the Electrode is Positively Correlated with the Bioelectricity of the Microbial Fuel Cell of Fisheries Wastewater

Microbial fuel cell (MFC) is a bioreactor utilizing bacteria as electrocatalysts to convert bioenergy from biomass into electrical energy. The aim of this research were to determine the effects of the electrode distance on the bacterial density and the electrical value generated by the MFC as well as to evaluate the ability of MFC in reducing the pollutant. Single chamber MFC system with various electrode distances including 2 cm, 4 cm, and 6 cm were assembled. The wastewater of fish pindang processing was used as the medium<br />for the MFC. The results showed that the distance had no effect on the biofilm density of the electrode and the reduction of the wastewater pollutant load. However, the distance affected the electrical value of the<br />MFC. Biofilm density on the MFC electrode after 120 hours was 0.65-6.46 CFU/ cm2. The highest voltage was obtained from the 6 cm electrode distance with the voltage 0.38±0.01 V. Positive correlation (R2 = 0.99)<br />between microbial density and electricity produced at the cathode was observed, but weak at the anoda (R2 = 0.47). The MFC system could decrease the BOD value up to 50.78% and COD up to 33.29%, however the TAN value was increased to 6 mg/L.

The Influence of Technological Conditions on Dielectric and Optical Properties of K0.5Bi0.5TiO3 Ceramics

Lead-free ceramics of potassium-bismuth titanate K0.5Bi0.5TiO3 were obtained by a conventional sintering method under various technological conditions. The dielectric permittivity (ε) and dielectric loss (tan(δ)) measurements for these ceramics were carried out in the temperature range from 293 K to 873 K with the frequency range from 0.1 kHz to 2 MHz. An increase in dielectric permittivity with an increasing sintering temperature was observed. For the sample obtained at 1313 K and a 3.5-hour sintering time, the value of ε was about 4.55·103 (f = 100 kHz) which is twice higher than the value of ε for the sample obtained at a temperature of 1298 K and a 7-hours sintering time. For all samples, the maximum value of dielectric permittivity was shifted towards higher temperatures with an increasing frequency, which is a characteristic features of ferroelectric relaxor materials. The dielectric properties of all materials were very similar, especially in the case of dielectric loss. The values of tan(δ) at room temperature varied from about 0.07 at 0.1 kHz to 0.1 at 2 MHz. The Raman studies were performed at room temperature. No significant changes were observed for different sintering temperatures and times for all samples. The presented material can be a starting point for the development of new ferroelectric relaxor materials.

The effect of nanoperlite and its silane treatment on thermal properties and degradation of polypropylene/nanoperlite nanocomposite films

The main goal of this study is to observe the exact effect of nanoperlite and its silane treatment on thermal behavior and degradation mechanism as well as thermomechanical properties of nanocomposites. In this regard, polypropylene (PP) with various contents of untreated nanoperlite and silane treated nanoperlite were prepared using a twin-screw extruder and an extrusion film blew machine. Regardless of the type, the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) tests show no chemical reaction between PP and nanoperlite and relatively good dispersion of nanoparticles was obtained in the system. The results of thermal studies represent a reduction in all the properties of nanoperlite/PP nanocomposites including thermal stability, while, the addition of silane treated nanoperlite shows less reduction and better thermal stability. Based on Flynn-Wall-Ozawa method, thermal degradation kinetics and mean activation energies of the untreated nanoperlite filled nanocomposites show higher values. Finally based on thermomechanical studies, treated nanoperlite-filled nanocomposites show lower values for tan D comparing to untreated nanoperlite-filled nanocomposites, as the storage modulus is reinforced and the loss modulus decreased. Overall, nanocomposites with 2–4% of treated nanoperlite showed nearly the same behavior of 4–6% of untreated nanoperlite filled nanocomposites and due to better dispersion, thermal and morphological properties, these films can be proper alternatives for packaging industries.

Medical grade polylactide, copolyesters and polydioxanone: Rheological properties and melt stability

Rheological measurements have shown that lactide-based copolymers with L-lactide content between 50 and 100 mol% with varying comonomers, as well as polydioxanone (PDX), can be used in additive manufacturing analogously to poly(L-lactide) (PLLA) if their melt behaviour are balanced. The results indicate that copolymers can be melt processed if the temperature is adjusted according to the melting point, and parameters such as the speed are tuned to conteract the elastic response.Small amplitude oscillatory shear (SAOS) rheology, thermal and chemical characterisation allowed us to map the combined effect of temperature and frequency on the behaviour of six degradable polymers and their melt stability. Values of complex viscosity and Tan δ obtained through nine time sweeps by varying temperature and frequency showed that the molecular structure and the number of methylene units influenced the results, copolymers of L-lactide with D-Lactide (PDLLA) or glycolide (PLGA) had an increased elastic response, while copolymers with trimethylene carbonate (PLATMC) or ε-caprolactone (PCLA) had a more viscous behaviour than PLLA, with respect to their relative melting points. PDLLA and PLGA require an increased temperature or lower speed when processed, while PLATMC and PCLA can be used at a lower temperature and/or higher speed than PLLA. PDX showed an increased viscosity compared to PLLA but a similar melt behaviour. Negligible chain degradation were observed, apart from PLGA.

Influence of the imaginary part of the dielectric layer on the bandwidth of metamaterial absorber and the design of broadband absorption

It is well known that dielectric layer imaginary part (or loss tangent of tan(δ)) plays a crucial role in modulating the absorption rate of metamaterial absorber (MA). However, there is not any systematic investigation into whether tan(δ) impacts resonance bandwidth of the MA. Herein, we investigated the dependence of resonance bandwidth of the MA on the change of tan(δ). Three kinds of absorbers with top layers of frequently used metallic patterns of square patch, cross, and strip were demonstrated. To facilitate comparison of the bandwidth, each case of tan(δ) was optimized for perfect absorption. Results proved that the bandwidths of the three absorbers were broadened greatly with tan(δ) increase. Their bandwidth enhancement factors are all at least 10. Based on this, this paper further makes some discussions on the design of broadband MA, which consists of three alternating stack of square patches and dielectric layers with large value of tan(δ) on top of a metallic board. >80% absorption of the resonance bandwidth of the triple-layer absorber can cover a frequency range of 3.689 THz. The relative resonance bandwidth of absorber can reach 138.893%, which is far higher than that of previous broadband absorbers using small value of tan(δ).

Dynamic mechanical behavior of flocked layer composite materials

A custom designed dynamic mechanical apparatus was constructed to measure the tan(δ) (loss tangent) properties of Flocked (layer) Energy Absorbing Materials (FEAM). Flocked Impact Energy Absorbing (IEA) materials derive their dynamic mechanical impact absorbing properties from the compressional deformation (bending, buckling) and inter-fiber friction of nominally upright flocked fibers in the flock fiber composite assembly. The reported work summarizes the dynamic mechanical, low strain, linear viscoelastic tan(δ) properties of FEAM composite layer structures at frequencies from 25 to 100 Hz and a temperature range of 0 °C–50 °C. The effect of tan(δ) at various flock densities (fibers/mm2) was also measured. These studies were carried out to gain information and insight into the role that a material’s dynamic mechanical properties have on the overall IEA performance of sport (and military) apparel pad structures. Results show that the tan(δ) of FEAM materials increases as the measuring frequency and flocked layer’s flock density increase. Tan(δ)’s behavior at various temperatures (0 °C–50 °C) did not follow an expected trend; the highest tan(δ) value was observed to occur at room temperature. Nevertheless, the obtained tan(δ) information on these various FEAM configurations should provide some guidance in designing optimized FEAM sport (and military) pad IEA composites.

Kinerja Microbial Fuel Cells Pada Pengolahan Limbah Cair Pemindangan Dengan Membran Separator Campuran Polimer Kitosan/PVA

Separator attched to MFC system can reduce the distance between cathode and anode and limit oxygen penetration to anode chamber. The use of Chitosan/polyvinyl alcohol (PVA) mixture polymer as membrane separator was expected to have ability to increase electron recovery from the substrate. The objectives of this research were to increase the standard quality of wastewater of salted boiled fish processing and to increase bioelectricity generation, through the membrane separator adding to MFC system. Separator polymer was made by blending 2% chitosan and 5% PVA solution, in different ratio of chitosan (K) and PVA (P) at 2:3 (K2P3), 1:1 (K1P1), 3:2 (K3P2), and without separator. The study was carried out to measure electricity generated and to analyse of BOD, COD and TAN of the wastewater. The K2P3 treatment showed the highest electricity generation with average voltage of 0.50±0.06 V, maximum current density 0,29 mA/cm2, and maximum power density 15.40 mW/cm2. The reduction of COD showed insignificantly different among treatments, but the reduction of BOD and TAN values showed significantly different. The BOD value reduced to56.54% in K2P3 treatment and the TAN value reduced to 92.73% in K1P1 treatment.Keywords : chitosan, microbial fuel cell, polyvinil alcohol, separator

Comparing the corrosivity of acidic species in petroleum fractions by raman spectroscopy, energy-dispersive spectrum and scanning electron microscopy

ABSTRACTThe main object of this work was to compare the corrosion powers of acidic species: naphthenic acid, fatty acid and aromatic acid which were found in petroleum fraction. They were blended into base oils to formulate three simulate oils (E, F and G) with the same TAN values of 2.3 mg KOH/g. AISI 316 steel surfaces immersed in oils were measured by Raman spectroscopy, energydispersive spectrum and scanning electron microscopy after 24, 48, 72 h to evaluate their corrosion. From the Raman images, the corrosion products were confirmed. Besides goethite (α-Fe(OOH)) in corrosion product E at 48 hours; magnetite (Fe3O4) in F at 24 hours; and hematite (α-Fe2O3 and α-Fe2O3) in G at 72hours, there were disordered carbons on steel E and ferric benzoate film on steel G. The contents of elements from EDS have markedly different characteristics, indicating that dominant corrosion products on steel samples resulted from three acidic species are different. The morphology in SEM also corroborated above data that corrosion products have difference. Combining the data of three measurements, the rank of corrosion power based on the formations of ferric oxides was determined: fatty acid > naphthenic acid > aromatic acid.

Effect of Effective Microorganisms (Em) and Molasses, Wheat Bran, and their Mixture in a Biofloc System on Microbial Protein Production, Water Quality, Growth Performance and Feed Utilization of Nile Tilapia (Oreochromis niloticus) Fingerlings.

The present experiment was carried out to investigate the effect of effective microorganisms, EM; carbohydrate sources as molasses, M; wheat bran, and their mixture in a Bio-floc (BF) system on microbial protein production, water quality, growth performance, and feed utilization of Nile tilapia (Oreochromis niloticus) fingerlings. Seven experimental treatments were designed as following: T1: control, fish were fed a basal diet without any addition of carbohydrate source. T2: T1 plus effective microorganisms (EM) in water media. T3: T1 with supplementary molasses (M) in water media. T4: T1 with supplementary wheat bran (WB) in water media. T5: T1 with supplementary of mixture from EM and M in the water media. T6: T1 with supplementary of mixture from EM and WB in the water media, and T7: T1 with supplementary of mixture from M and WB in the water media. Fish in each tank were fed with one of the experimental diets containing 22.49 % crude protein and 471.60 Kcal. gross energy /100g DM at feeding rate of 3% of the actual fish live body weight, two times daily (9.00am and 2.00 pm) for six days a week for 90 days experimental period. Fish were distributed randomly into fourteen indoor fiberglass tanks. Each treatment was conducted in two indoor circular fiberglass tanks of 1m diameter filled with 1000 litter of fresh water. Nile tilapia fingerlings with an average initial body weight of 47.5±0.05 (g/fish) were randomized stocked at the rate of 42 fish / tank. The results showed the followings:The water quality parameters showed no significant differences in water temperature (C0), pH value and DO (mg/l); however, there were marked differences in the values of total ammonia nitrogen (TA-N, mg/l) and Bio-floc (BF) concentrations (mg/l), with high values of TA-N and BF in tanks' water supplemented with different carbohydrate sources than control, especially with T6 which containing mixture of EM and WB in water media followed by T4 (WB), T3 (M), T5 (EM+M), T2(EM), and T6 (M+WB), respectively compared with T1 (control without carbohydrate source).Fish growth performance and feed utilization were significantly (P≤ 0.05) increased with EM and carbohydrate source supplementation than control. Also, T6 which containing a mixture of EM and WB gave the highest performance followed by WB (T4) and M (T3), respectively.Finally, the present results recommended the use of a mixture of effective microorganisms and wheat bran as a carbohydrate source in fish water tanks for optimal performance with best impacts on intensive tilapia culture reared under zero water exchange system.