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Article
Publication date: 9 February 2015

Yasamin Soleimanian, Mohammad A. Sahari and Mohsen Barzegar

The purpose of this study was to investigate the efficiency of low temperature fractional crystallization to increase polyunsaturated fatty acid (PUFA) content of fish…

Abstract

Purpose

The purpose of this study was to investigate the efficiency of low temperature fractional crystallization to increase polyunsaturated fatty acid (PUFA) content of fish oil. Effects of temperature, stages of crystallization, rate of cooling, agitation and addition of primary nucleus on separation efficiency were evaluated. Low temperature crystallization of triacylglycerols (TAGs) was used to increase PUFA content of fish oil (initial PUFA content ∼30 g/100 g oil).

Design/methodology/approach

To optimize the fractionation process, the effect of fractionation temperature (7, 5, 0 and −5°C), crystallization procedures, cooling rate, agitation and addition of primary nucleus on PUFA content was evaluated.

Findings

The best relationship between PUFA concentration (45.8 g/100 g oil) and PUFA yield (51.5 per cent) was attained by performing two-stage crystallization of TAGs at the final temperatures of 5 and 0°C under slow cooling rate (3°C h−1 for first fractionation procedure and 0.7°C h−1 for second stage, until the final fractionation temperature, 0°C, was reached) and slow agitation (3 rpm) and in the presence of primary nucleus, which resulted in 50 per cent increase in PUFA content over the original fish oil.

Practical implications

Determination of iodine and saponification values, refractive index, solid fat content, melting point, cholesterol content of original oil and final fractionated product with the highest PUFA ratio showed that fractionation significantly alters physical and chemical properties of the fraction.

Originality/value

Comparison of iodine value, saponification value, refractive index, solid fat content, melting point and cholesterol content of original oil and the final fractionated product (with the highest PUFA ratio) showed that the fractionation process significantly alters mentioned properties of the initial oil.

Details

Nutrition & Food Science, vol. 45 no. 1
Type: Research Article
ISSN: 0034-6659

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Article
Publication date: 8 June 2012

B. Pajin, I. Radujko, Z. Šereš, D. Šoronja Simović, J. Gyura and M. Sakač

Investigated milk fat fraction differs in physical attributes, first of all in melting point and solid fat content and its influence on crystallization process of cocoa…

Abstract

Purpose

Investigated milk fat fraction differs in physical attributes, first of all in melting point and solid fat content and its influence on crystallization process of cocoa butter i.e. chocolate mass. It means that this fraction slows down crystallization rate, decreases melting point of mixture with cocoa butter and causes chocolate softness. It is very important for quality of chocolate especially chocolate with nuts or sunflower kernel. The aim of this paper was to investigate the influence of low‐melting (26°C) milk fat fraction on crystallization processes in chocolate mass and define the optimal concentration of this fraction with suitable precrystallization temperature time regime. Solid fat content of chocolate which designates the influence of precrystallization changes in chocolate mass with addition of milk fat fractions was investigated.

Design/methodology/approach

The precrystallization was performed in a laboratory crystallizer that is in a modified Brabender pharinograph, which measures the rheological characteristics as indirect parameter of crystallization properties of chocolate mass depending on milk fat fraction concentration and precrystallization temperature. The experiments were performed according to the factorial plan 32 (two factors on three levels) and the results are statistically treated.

Findings

The results showed that the optimal conditions for achieving the satisfactory tempering rate (optimal concentration of crystals in chocolate mass) are addition of 3 per cent low‐melting milk fat fraction and precrystallization temperature of 25°C.

Originality/value

The addition of high‐melting milk fat fraction slows down the chocolate mass crystallization more then low‐melting milk fat fraction. Investigated fraction influenced decreasing in solid fat content of chocolate regardless of precrystallization temperature.

Details

British Food Journal, vol. 114 no. 6
Type: Research Article
ISSN: 0007-070X

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Article
Publication date: 20 March 2009

C. Zhang, Y. Huang, Y. Liu, S. Wang and X. Zhang

The purpose of this paper is to study the isothermal and nonisothermal crystallisation kinetics of pure polypropylene (PP), 1 kGy pre‐irradiated PP and 1 kGy…

Abstract

Purpose

The purpose of this paper is to study the isothermal and nonisothermal crystallisation kinetics of pure polypropylene (PP), 1 kGy pre‐irradiated PP and 1 kGy pre‐irradiated PP/syndiotactic 1,2‐polybutadiene (s‐1,2 PB) (90/10) blends by differential scanning calorimetry.

Design/methodology/approach

The Avrami equation, modified Avrami equation, Ozawa equation and the treatment by combining the Avrami and Ozawa equation were used to analyse the isothermal and nonisothermal crystallisation of various samples.

Findings

The s‐1,2 PB acted as a heterogeneous nucleation agent during the crystallisation of the PP/s‐1,2 PB blends and accelerated the crystallisation rate. The Avrami exponent n of the blends implied that the isothermal crystallisation kinetics of the blends followed a three‐dimensional growth via heterogeneous nucleation. The modified Avrami equation was limited to describe the nonisothermal crystallisation process of pure PP and 1 kGy pre‐irradiated PP, but it was successful for the blends. The treatment by combining the Avrami and Ozawa equation described appropriately the nonisothermal crystallisation process and obtained the kinetic parameter F(T) with specific physical meaning. The crystallisation activation energy for isothermal crystallisation and nonisothermal crystallisation of the blends was reduced due to the s‐1,2 PB acting as a heterogeneous nucleating agent during the crystallisation of the blends and accelerating the crystallisation rate.

Research limitations/implications

The Avrami equation, modified Avrami equation, Ozawa equation and the treatment by combining the Avrami and Ozawa equation were compared for analysis of the isothermal and nonisothermal crystallisation of samples. The crystallisation activation energy for isothermal crystallisation and nonisothermal crystallisation was also calculated according to the Arrhenius and the Kissinger method.

Practical implications

The fundamental research on the crystallisation properties of PP/s‐1,2‐PB blends is essential to understand the mutual effects of two components on their crystallisation mechanisms, facilitating to improve the mechanical properties of the final materials.

Originality/value

The isothermal and nonisothermal crystallisation behaviours of PP/s‐1,2 PB blends, especially pre‐irradiated PP/s‐1,2 PB blends, have not been studied systematically yet, though PP/s‐1,2 PB blends were promising materials in terms of both PP toughening and the application of s‐1,2 PB thermal plastic elastomer.

Details

Pigment & Resin Technology, vol. 38 no. 2
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 14 June 2018

Katrin Wudy, Maximilian Drexler, Lydia Lanzl and Dietmar Drummer

The thermal history during laser exposure determines part properties in selective laser sintering (SLS). The purpose of this study is to introduce a new measurement…

Abstract

Purpose

The thermal history during laser exposure determines part properties in selective laser sintering (SLS). The purpose of this study is to introduce a new measurement technique based on a CO2 laser unit combined with a high-speed DCS. A first comparison of the thermal history during laser exposure measured with Laser-high-speed-(HS)-differential scanning calorimetry-(DSC) and in SLS process is shown.

Design/methodology/approach

This Laser-HS-DSC allows an imitation of the SLS-process in a very small scale, as the sample is directly heated by a CO2 laser. For this study, the laser power and the impact time is varied for determining temperature and achieved heating rates. Consequently, the temperature levels measured by the Laser-HS-DSC are compared with measurements in SLS-process.

Findings

The influence of laser power and impact time on resulting maximum temperatures und heating rates during laser exposure are investigated. With increasing laser power and impact time the maximum temperature rises up to approximately 450°C without material degradation. The heating rate increases up to an impact time of 3 ms and stays almost equal for higher durations.

Research limitations/implications

The Laser-HS-DSC experiments are based on few particles limiting a complete comparison with SLS process. In SLS, one volume element is exposed several times. In this study the PA12 material was exposed only once.

Originality/value

For the first time, laser sintering experiments can be transferred to a laboratory scale to analyze the influence of laser exposure on resulting temperature field during laser exposure without superimposing effects.

Details

Rapid Prototyping Journal, vol. 24 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

Content available
Article
Publication date: 4 January 2021

Radosław Wajman

Crystallization is the process widely used for components separation and solids purification. The systems for crystallization process evaluation applied so far, involve…

Abstract

Purpose

Crystallization is the process widely used for components separation and solids purification. The systems for crystallization process evaluation applied so far, involve numerous non-invasive tomographic measurement techniques which suffers from some reported problems. The purpose of this paper is to show the abilities of three-dimensional Electrical Capacitance Tomography (3D ECT) in the context of non-invasive and non-intrusive visualization of crystallization processes. Multiple aspects and problems of ECT imaging, as well as the computer model design to work with the high relative permittivity liquids, have been pointed out.

Design/methodology/approach

To design the most efficient (from a mechanical and electrical point of view) 3D ECT sensor structure, the high-precise impedance meter was applied. The three types of sensor were designed, built, and tested. To meet the new concept requirements, the dedicated ECT device has been constructed.

Findings

It has been shown that the ECT technique can be applied to the diagnosis of crystallization. The crystals distribution can be identified using this technique. The achieved measurement resolution allows detecting the localization of crystals. The usage of stabilized electrodes improves the sensitivity of the sensor and provides the images better suitable for further analysis.

Originality/value

The dedicated 3D ECT sensor construction has been proposed to increase its sensitivity in the border area, where the crystals grow. Regarding this feature, some new algorithms for the potential field distribution and the sensitivity matrix calculation have been developed. The adaptation of the iterative 3D image reconstruction process has also been described.

Details

Sensor Review, vol. 41 no. 1
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 4 October 2011

Cynthia Gomes, Nahum Travitzky, Peter Greil, Wilson Acchar, Hansu Birol, Antonio Pedro Novaes de Oliveira and Dachamir Hotza

This paper seeks to detail the fabrication of a glass‐ceramic substrate, based on the LiO2‐ZrO2‐SiO2‐Al2O3 (LZSA) system, by laminated object manufacturing (LOM) using…

Abstract

Purpose

This paper seeks to detail the fabrication of a glass‐ceramic substrate, based on the LiO2‐ZrO2‐SiO2‐Al2O3 (LZSA) system, by laminated object manufacturing (LOM) using water‐based cast tapes.

Design/methodology/approach

Small amounts of ZrSiO4 were added to control the thermal expansion coefficient (TEC) of the original glass‐ceramic (LZSA5Zr: LZSA+5 wt% ZrSiO4). In order to verify the influence of the amount and nature of crystalline phases on the thermal and dielectric behavior of the material, LZSA and LZSA5Zr laminates were sintered at 700°C for 30 min and crystallized at either 800 or 850°C for 30 min.

Findings

LZSA laminates (sintered and crystallized at 700 and 800°C, respectively) exhibited a relative density of ∼90 percent, a dielectric constant of 8.39, a dielectric loss tangent of 0.031 and TEC of 5.5×10−6 K−1 (25‐550°C). The addition of 5 wt% ZrSiO4 to original LZSA glass‐ceramics led to a nearly constant TEC value of 6×10−6 K−1 throughout the whole temperature interval (25‐800°C). Dielectric properties of LZSA5Zr did not show any remarkable change when compared to original LZSA.

Originality/value

The thermal, mechanical and electrical properties of LZSA glass‐ceramic laminates fabricated by LOM makes them potential candidates for substrate applications.

Details

Rapid Prototyping Journal, vol. 17 no. 6
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 30 March 2010

Hedieh Alavi Talab, Mehdi Ardjmand, Abbasali Motallebi and Reza Pourgholam

Extraction and purification of Hypophthalmichthys molitrix fish oil by urea complex formation were made at −5, +1 and +5 C, respectively. Omega‐3 polyunsaturated fatty…

Abstract

Purpose

Extraction and purification of Hypophthalmichthys molitrix fish oil by urea complex formation were made at −5, +1 and +5 C, respectively. Omega‐3 polyunsaturated fatty acids (PUFA) have proved to be beneficial in atherosclerosis, arrhythmia and hypertriglyceridemia. Starting with the hypothesis that the observed low cardiovascular morality could be related to marine diet, which contains omega‐3 PUFA.

Design/methodology/approach

Fish oil was extracted by Bligh and Dyer method from the muscle tissue and after, the PUFA concentrates produced by urea complexation and the oil samples were stored at −70 C. The observed results show that the rate of omega‐3 extraction has been increased while saturated and long chain monosaturated fatty acids decreased during this process.

Findings

Eicosapentaenoic acid (EPA) has a higher tendency to form urea adducts than the other two major n‐3 PUFAs, especially at low temperatures. The optimum temperature for maximum recovery of EPA is about 1 C. The amount of extracted omega‐3 in H. molitrix oil were 20.58 per cent wt of total extracted oil and by subsequent purification increased to 68 per cent wt at 1 C, 36.82 per cent wt at +5 C and 22.53 per cent wt at −5 C of total extracted oil.

Practical implications

Omega‐3 PUFA have proved to be beneficial in atherosclerosis, arrhythmia and hypertriglyceridemia. Starting with the hypothesis that the observed low cardiovascular morality could be related to marine diet, which contains omega‐3 PUFA. In order to reduce the risk of cardiovascular diseases, emphasis has now been placed on the increased consumption of fish and fish products which are rich in PUFA.

Originality/value

The amount of extracted omega‐3 in H. molitrix oil were 20.58 per cent wt of total extracted oil and by subsequent purification increased to 68 per cent wt at 1 C, 36.82 per cent wt at +5 C and 22.53 per cent wt at −5 C of total extracted oil. Due to the low price of H. molitrix in comparison to other ocean fish sources, as well as, its availability in all seasons, higher level of ω3‐fatty acids, H. molitrix species has a good potential for ω3‐fatty acids production by extraction and subsequent purification.

Details

Nutrition & Food Science, vol. 40 no. 2
Type: Research Article
ISSN: 0034-6659

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Article
Publication date: 1 January 1966

N.R. Hemming

The temperatures which will typically be encountered by various parts of a hypersonic air breathing engine at different Mach numbers are indicated in FIG. 1. A limited…

Abstract

The temperatures which will typically be encountered by various parts of a hypersonic air breathing engine at different Mach numbers are indicated in FIG. 1. A limited gain can be expected from the employment of cooling systems but in general the need for materials possessing heat resisting properties which are markedly superior to those conventionally used, such as the Nimonic range, is apparent at approximately Mach 4. Combustor flame stabilizing equipment for example must survive as an item of structure at temperatures around 1,300 deg. C. for Mach 4 and 1,500 deg. C. for Mach 5. Intake leading edges and ducts containing intake air are two further areas requiring the use of new high temperature metals once Mach 5 has been significantly exceeded. The combustor gas temperatures shown in FIG. 1, even allowing for limited cooling, require the use of a material capable of operating with a hot face temperature of 2,000 deg. C. or above. In this instance the material might be used as a non‐structural lining designed to lean on the cooler load‐carrying structure. In each of these instances the material is subjected to the effects of a high velocity oxidizing atmosphere.

Details

Aircraft Engineering and Aerospace Technology, vol. 38 no. 1
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 January 2008

Jian‐hong Yang, Gui‐fang Li and Hui‐lan Liu

Choosing suitable high‐K gate dielectrics to reduce the off‐state leakage (Ioff) by edge direct tunneling mechanism, demonstrating that the decreased Ioff increase…

Abstract

Purpose

Choosing suitable high‐K gate dielectrics to reduce the off‐state leakage (Ioff) by edge direct tunneling mechanism, demonstrating that the decreased Ioff increase significantly when the gate dielectrics permittivity are above 25. The purpose of this paper is to report that HfSiON and HfLaO are promising gate dielectrics.

Design/methodology/approach

The off‐state gate current, drain current, and substrate current are investigated. The IdVgs characteristics for the 50 and 90 nm NMOSFET with various gate dielectrics are studied. Edge direct tunneling current (IEDT) with various gate dielectrics including SiO2, Si3N4 and HfO2 are compared and this paper also examines the IEDT with HfSiON and HfLaO gate dielectrics.

Findings

IEDT prevails over conventional gate‐induced drain‐leakage current (IGIDL), subthreshold leakage current (ISUB), band‐to‐band tunneling current (IBTBT) and it dominates off‐state leakage current. A large increase in off‐state leakage current occurs for smaller devices due to increase in IEDT at high Vdd. Although IEDT is decreased with increase in gate dielectrics permittivity K. The authors found fringing induced barrier lowering (FIBL) which could introduce significant off‐state leakage current for K>25. Fortunately, the IEDT with HfSiON and HfLaO gate dielectrics which are two‐five orders of magnitude lower than that of SiO2, furthermore, FIBL for HfSiON and HfLaO gate dielectrics are inconspicuous. Moreover, HfLaO and HfSiON have superior electrical performance and thermal stability.

Originality/value

Both edge direct tunneling and FIBL are considered to alternate high‐K gate dielectrics for nano‐scale MOSFET.

Details

Microelectronics International, vol. 25 no. 1
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 1 December 2004

Fang Kehong

In recent years, with the development trends towards lighter, shorter and smaller high performance and high reliability electronic products, printed circuit boards have…

Abstract

In recent years, with the development trends towards lighter, shorter and smaller high performance and high reliability electronic products, printed circuit boards have ceaselessly been growing in terms of higher density and layer count. At present, conventional FR‐4 laminate, which is reinforced by glass fabric, has become the universal purpose base material because of its excellent adhesion, good electrical insulation and mechanical properties. However, with its relatively low glass transition temperature (Tg) of approximately 135°C, large coefficient of thermal expansion in the z‐axis direction, poor thermal resistance and propensity for resin smear while drilling, normal FR‐4 is severely limited in high performance applications, especially for multilayer board fabrication, and is used only for multilayer boards with layer counts below ten. Furthermore, conventional FR‐4 is usually cured using dicyandiamide, which could potentially cause insulation deterioration of the printed circuit boards and vulnerability in terms of delamination under high temperature treatment. These effects could degrade the reliability of PCBs and therefore, base material suppliers have focused on improving the Tg and thermal resistance to broaden the operating window of conventional FR‐4.

Details

Circuit World, vol. 30 no. 4
Type: Research Article
ISSN: 0305-6120

Keywords

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