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Article
Laser-Human Skin Interaction: Analytical Study and Optimization of Present Non-Ablative Laser Resurfacing

Author: W.K. Hamoudi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2008 Volume: 4 Issue: 3 Pages: 5-11
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

There have been numerous of articles, reports and papers published on non-ablative laser resurfacing, showing the treatment of a wide range of tissue types, laser systems and doses and subject ages. Despite the fact that laser-skin interaction is affected when changing any of the laser parameters, many authors announced good results for the same skin conditions and disorders although different laser beam parameters were used. In their procedures they have adopted trial and error technique – a procedure that could cause some problems and side effects to patients. For random samples taken from the published articles [11-18] on non-ablative resurfacing, the authors used wide range of laser wavelengths (585-1320) nm, number of treatments (1-7) and fluences (2-179) J/cm2. In addition, they used a very wide range of laser pulse durations (6ns-40ms) and some employed cooling while others did not. This article analyzes the results presented by some authors in order to define a better guide line for the use of lasers in this field.


Article
Structural Characteristics Study of Indium Diffusion in Silicon Using a Pulsed Nd:YAG Laser

Authors: W.K. Hamoudi --- R.O. Dala Ali
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2005 Volume: 1 Issue: 1 Pages: 34-38
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In the current study, a pulsed Nd:YAG laser was employed to induce indium diffusion in silicon by laser irradiation of a thin indium film deposited on silicon. The work was aimed to study the structural characteristics changes of the irradiated region resulting from varying laser pulse energy within the range (0.25-0.53)J and varying silicon temperature from 300K to 373K during laser irradiation. Optical and scanning electron microscopes were used for the surface topography study of the samples. The study showed formation of linear cracks, protrusions and craters depending on the laser energy used. The indium diffusion depth within the silicon was determined using an energy dispersive spectra (EDS). This was done when illuminating at the laser melting threshold at substrate temperature of 373K and when illuminating at higher laser energy and substrate at room temperature (300K). the diffusion depth increased and the impurity concentration at the surface decreased as laser energy got higher. Higher substrate temperature helped increasing the impurity concentration at the surface.


Article
Band Diagram of p-PbTe/n-Si Heterostructure

Authors: R.A. Ismail --- W.K. Hamoudi --- Y.Z. Dawood
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2005 Volume: 1 Issue: 2 Pages: 27-30
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In the present work, the energy band diagram of p-PbTe/n-Si heterojunctions made by thermal evaporation of a polycrystalline PbTe layer deposited on a monocrystalline Silicon substrate is constructed. Based on I-V and C-V measurements, the band offsets ΔEC and ΔEV are found experimentally to be 270mV and 610mV respectively at 300K.


Article
New High Angular Resolution Detection System for Direction Recognition

Authors: H.H. Habib --- W.K. Hamoudi --- R.A. Ismail
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2005 Volume: 1 Issue: 3 Pages: 27-32
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

A digital angular resolution detection device using linear detector arrays has been designed and fabricated in two models; with accuracy better than (r1q) and (r2q) respectively. The principle of operation is based on encoding the radiation angle of arrival by using a code mask based on random fractal generation.


Article
Modeling of 3-D Keyhole CO2 Laser Welding of Steel

Authors: W.K. Hamoudi --- A.K. Hamoudi --- S.A. Salih
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2010 Volume: 6 Issue: 1 Pages: 15-23
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

A mathematical 3-D model for keyhole CO2 laser welding of thick C/Mn steel sheets under variety of laser material processing conditions is presented. The analysis yields profile of the melt pool and compare it with experiments. The model combines a moving point source for the top part of the weld and a moving line source for the parallel sided region of the weld (stem). This concept produces weld profiles that have good qualitative agreement with the experiments. Mathematical model and computer program were constructed to solve two basic heat conduction equations for the moving point and line sources. The excellent match of theoretical and experimental weld profiles will make this work a good candidate for laser welding prediction in robotic networks.


Article
HAZ and Melt Limits of 3-D CO2 Laser welding

Authors: A.K. Hamoudi --- W.K. Hamoudi --- S.A. Salih
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2011 Volume: 7 Issue: 2 Pages: 11-17
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

An analytical and numerical 3-D model for keyhole CO2 laser welding of thick C/Mn steel sheets is constructed to study the heat affected zone (HAZ) and melt limits. Simulation results are compared with experimental investigations under variety of laser material processing conditions. The model combines a moving point source for the top part of the weld and a moving line source for the parallel sided region of the weld. The good match of theoretical and experimental results makes the model a good tool to predict the HAZ volume in which microstructure changes may occur. Such prediction is useful in the investigation of hardening and the cracks formation during laser welding.


Article
Non-ablative Tattoo Removal Using Fundamental and Second Harmonic Nd:YAG Laser (Histological Observations)

Authors: T.A.T. Ibrahim --- S.I. Hassan --- W.K. Hamoudi
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2013 Volume: 9 Issue: 4 Pages: 11-16
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In laser tattoo removal, selective photothermolysis permits the selective destruction of tattoo pigment molecules with very limited damage to surrounding tissue. To maximize the breakup of tattoo ink, the energy density (fluence), wave-length, and pulse duration of the laser need to be optimized. White domesticated Albino rabbits were used in our trials. Each received simultaneous injections of a color pigment tattoo while under general anesthesia, followed by sessions of Q-switched Nd: YAG (1064 and 532 nm), (100-800) mJ, and 5 and10 ns laser pulses for tattoo removal. The spectroscopic properties of black, brown, green, blue and red tattoo inks were studied in our trial. Laser fluence damage threshold of tattooed tissue was also investigated in order to select the optimized conditions for obtaining scar-free skin following tattoo removal. A histological observation of laser treated tissue, before and after laser treatment, was then performed using optical microscopy. Histological images of the biopsies taken after thirty days of laser treatment of both black and brown tattoos showed a marked reduction in pigment granules’ size, with no appearance of hyperplasia, inflammatory cells, or vacuolations. Our results suggest that the coexistence of macrophages is responsible for actively phagocytosing the laser-dispersed tattoo pigment. Skin biopsies have demonstrated local redistribution of ink granules. In addition to shuttering tattoo particles, the laser created some vacuolations, adding extra mechanical damage to the pigment.


Article
Wideband (0.6-11) micron Angle Deposited Thin Te:S Laser Detector

Authors: W.K. Hamoudi --- R.A. Ismail --- R.S. Abid --- M.R. Ismail
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2005 Volume: 1 Issue: 4 Pages: 3-14
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

A study of nanostructural, optical and electrical characteristics of obliquely deposited thin sulfur-doped films is presented. The aim was to develop a wideband (0.6-11) micron laser detector operating at room temperature with no need to biasing or amplification. The deposition angle had a decisive role on the detector specifications, namely its detectivity and response time. At deposition angle of 70 deg, the maximum detectivity was achieved 3x10^9 W-1.Hz1/2.cm while at 60 deg a fastest response 1 microsecond was obtained.


Article
Improvement of Wound Healing in Rabbit Skin by Low Level Polarized Laser Light

Authors: N. Majid --- E.I. Jameel --- A.M. Ali --- R.A. Ismail --- et al.
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2013 Volume: 9 Issue: 4 Pages: 29-32
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

Living cells require energy to perform biological processes and functions. Low level lasers stimulate the basic energy processes in the mitochondria and help the production of Adenosine Tri-Phosphate (ATP)–the primary biological cell energy source needed for such activities. Full-thickness, parallel wounds in four domesticated Albino rabbits were surgically induced. The control wounds were left without laser treatment, whereas other wounds received daily laser treatments using laser energy fluence of 5 J/cm2 for rabbit 1; 4.5 J/cm2 for rabbits 2 and 3; and 3.5 J/cm2 for rabbit 4. Various polarization directions of the 660 nm low level (5 mW) diode laser were used to heal the induced wounds. The laser beam’s plane of polarization with respect to the wound line played an important role in the healing results. The fastest healing was completed in 16 day-time using a parallel orientation of polarized laser beam, while the perpendicular orientation of the polarized laser beam healed at lower rate, and the 45o polarization orientation of the laser beam gave poorest healing results. Laser photons of the parallel orientation of polarization interact with a chromophore located within the tissue. Laser illumination of wound can raise the energy of the cells and generate new collagen and fibroblast tissues, because electron excitation and de-excitation are vital in the mitochondrial respiratory chain. Wounds illuminated with a polarized laser in a plane parallel (Lll) to the wound line built new cells which filled the wound at a very fast rate and in a more homogeneous manner. The transverse orientation (L┴) of the laser beam helped filling the cells but stacking them in the orthogonal direction which required longer healing time.

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