Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : dispersion


Consistency Characteristics of Dispersive Clays

Roaa H. Ismael; Mohammed Y. Fattah; Mohammad F. Aswad

Engineering and Technology Journal, 2021, Volume 39, Issue 12, Pages 1753-1759
DOI: 10.30684/etj.v39i12.1650

Dispersive soils are characterized by three features: (1) unstable structure, (2) they are readily flocculate in water, and (3) very erodible. The use of dispersed clay soils in hydraulic structures, dams and road dams can cause serious engineering problems when this soil is not identified and used befittingly. There is a simple way to determine soil dispersion and more difficult to measure dispersion.  (Atterberg’slimits) (grain size analysis), and (visible classification) are not enough to recognize between (normal clays) and (dispersive clays).ASTM tests can identify dispersive clay, these include: (double hydrometer test), (chemical tests), (Crumb test), and (Pinhole test). In this paper, the dispersed soil has been artificially prepared by adding Na2CO3  to  natural clay in different proportions. The proportions are 5%, 15%, 25%, 30%, 35%, and 40% by weight. The target of this investigation is to investigate the effect of degree of dispersion of the soil on Atterberg limits. The study showed that the percentage of dispersion increases  with Atterberg’slimits  and the dispersion ratio and the plasticity index relationship are related by a direct relationship.

Beneficiation of Low Grade Calcium Bentonite Claystone

Hijran Z. Toama; Abdul-Wahab A. Al-Ajeel; Ekhlas M. Abdullah

Engineering and Technology Journal, 2018, Volume 36, Issue 5A, Pages 546-554
DOI: 10.30684/etj.36.5A.10

The beneficiation of Ca-bentonite claystone has been studied with dispersion sedimentation technique using polyionic salts as dispersant.The claystone is located in the Western Desert of Iraq. It is of a low grade, associated with different amount of clay and non-clay mineral impurities. Calcite (CaCO3) constitutes the major proportion of these impurities. Various parameters; solid concentration, dispersant amount (e.g. sodium tripolyphosphate, and tetrasodium pyrophosphate), conditioning time, and centrifugal sedimentation speed and time on the efficiency of the beneficiation process were investigated and followed through the measurement of CaO% and cation exchange capacity (CEC) values of the upgraded claystone concentrate. Centrifugal sedimentation were tested to separate the impurities from the clay suspension. Design experiments by Taguchi method, orthogonal array L16, was used for optimizing the different process parameters of the beneficiation process. Experiments were conducted at different solid concentrations (1, 3, 5, 7) wt.%, dispersion agent amount (0.2, 0.4, 0.6, 0.8) wt.%, conditioning time (5, 10, 15, 20) min, centrifugal sedimentation speed (500, 600, 700, 800) rpm, and centrifugal time (5, 10, 15, 20) min. The optimum beneficiation conditions obtained from the experimental work are, 7 wt.% solid concentration, 0.8 wt.% of dispersant, 15 min conditioning time attachment of the dispersant agent with the bentonite slurry, 800 rpm centrifugal speed, for 10 min time. Under studied condition, tetrasodium pyrophosphate showed better output t for achieving good beneficiation of bentonite clay from dilute crude slurry.

Erosion and dispersion of sandy soil with addition of fine materials

Ibrahaim M. Al-Kiki

Engineering and Technology Journal, 2013, Volume 31, Issue 3, Pages 470-483

For a better understanding of the performance of earth structures, it is essential to define and evaluate the variables that determine the erosion and dispersion of soils. A laboratory study has been carried out to characterize the soil internal erosion due to the water flow and the effect of fine materials percents on the erosion and dispersion of sandy soil.
A double hydrometer test, crumb test, slacking test and pinhole erosion test were conducted to investigate the soil dispersibility characteristics. Sandy soil samples were collected from a region in Mosul city – North of Iraq, and treated with different percents of fine materials of clayey soil, these percents were ranged from (0 – 80 %) of the dry weight of sandy soil.
The results showed that, the addition of fine materials enhanced both the compaction and dispersibility characteristics of sandy soil. As the fine materials increases, the soil resistance to internal erosion increased. So, the pinhole erosion test was the more reliability test to classify the soil according to the dispersibility.

Design of Low Dispersion Flattened Optical Fiber

Alaa Hussein Ali

Engineering and Technology Journal, 2010, Volume 28, Issue 16, Pages 5317-5326

Dispersion of the transmitted optical signal causes distortion for both digital and analog transmission along optical fibers. When considering the major implementation of optical fiber transmission which involves some form of digital modulation, then dispersion mechanisms within the fiber cause broadening of the transmitted light pulses as they travel along the channel. This paper demonstrates that non-zero dispersion flatting optical fiber is achievable with dispersion extended over
more than spectral range of 300nm. A total dispersion of (0.0398444 ps/nm.km) is obtained due to a design of an optical fiber with triple-clad at wavelength of 1551nm. Also the flatting optical fiber is tested using computer simulation at two distances at 50km and 100km.

FM Mode-Locking Fiber Laser

Inmar N. Ghazi; Waleed Y. Hussein; Salam Sami M. Salih

Engineering and Technology Journal, 2008, Volume 26, Issue 12, Pages 1534-1549

In this paper the study of Frequency Modulation Harmonic Mode-locking for
Ytterbium Doped Fiber Laser is presented. The model studied, uses ytterbium-doped,
single mode fiber pumped by 976 nm laser source is used with 150 mW pumping
power to produce 1055 nm output laser and Frequency Modulation Harmonically
Mode-Locked by MZI optical modulator. The effect of both normal and anomalous
dispersion regimes on output pulses is investigated. Also, modulation frequency effect
on pulse parameters is investigated by driving the modulator into different frequencies
values.
This study shows the stability of working in anomalous dispersion regime and the
pulse compression effect is better than counterpart normal regime, due to the
combination effect
of both negative(Group velocity dispersion), GVD and nonlinearity. Also it shows the
great effect of modulation frequency on pulse parameters and stability of the system.
Model-locking fiber laser master equation is introduced, and using the assumed pulse
shapes for both dispersion regimes after modifying (Ginzburg-Landau equation), GLE
and by applying the moment method, a set of five ordinary differential equations are
introduced describing pulse parameters evolution during each roundtrip.To solve these
equations numerically using fourth- fifth order, Runge-Kutta method is performed
through MatLab 7.0 program.