H.264 Mapping Strategies for Robust Video Streaming over IEEE 802.11e WLAN

Umar Iqbal Choudhry,JongWon Kim 한국정보과학회 2005 한국정보과학회 학술발표논문집 Vol.32 No.2

In this paper we propose several mapping schemes for streaming video generated by state?of?the?art H.264 codec over IEEE 802.11e enabled wireless LANs. The schemes take advantage of both 802.11e’s QoS mechanism and some novel features of the H.264 codec, so as to protect the most important information in terms of visual quality and reduce distortion under network congestion. The proposed methods are evaluated by means of the H.264 reference software codec, network simulation, and objective video quality measurements. Results show that the proposed methods achieve a robust and error resilient H.264 video streaming over wireless LANs than traditional best?effort streaming.

Structural and optical properties of single-crystalline ultraviolet-emitting needle-shaped ZnO nanowires

Umar, Ahmad,Kim, S.H.,Kim, J.H.,Park, Y.K.,Hahn, Y.B. Elsevier 2007 Materials letters Vol.61 No.27

<P><B>Abstract</B></P><P>Well-crystallized with excellent optical properties, needle-shaped ZnO nanowires have been synthesized on silicon substrate in a high density via the thermal evaporation of metallic zinc powder without the use of catalysts or additives. Extensive structural analysis showed that the grown nanowires are highly crystalline with the wurtzite hexagonal phase, grown along the [0001] in the c-axis direction. The presence of an optical-phonon <I>E</I><SUB>2</SUB> mode in Raman spectrum at 437?cm<SUP>− 1</SUP> and sharp and strong UV emission at 379?nm with no green emission in the room-temperature photoluminescence (PL) spectrum confirms good crystallinity with the excellent optical properties for the deposited nanowires.</P>

ZnO Nanorods Based Hydrazine Sensors

Umar, Ahmad,Rahman, M. M.,Hahn, Yoon-Bong American Scientific Publishers 2009 Journal of nanoscience and nanotechnology Vol.9 No.8

<P>Electrochemical sensor for the detection of hydrazine has been fabricated at the surface of gold electrode modified with ZnO nanorods. The ZnO nanorods were grown by non-catalytic simple thermal evaporation process by using metallic zinc powder in the presence of oxygen at low-temperature. The detailed structural studies revealed that the as-grown ZnO nanorods are well-crystalline with the wurtzite hexagonal phase and grown along the [0001] direction in preference. A good and reproducible sensitivity of 4.76 microA cm(-2) microM(-1) has been obtained from the fabricated hexagonal-shaped ZnO nanorods based electrochemical sensor. The response time of the fabricated sensor was less than 10 s with a linear range from 0.2 to 2.0 microM and correlation coefficient of R = 0.9914. The limit of detection (LOD), based on S/N ratio was estimated to be 2.2 microM.</P>

Formation of hierarchical ZnO nanostructures ''nanocombs'': Growth mechanism, structural and optical properties

Umar, A.,Kim, S.H.,Hahn, Y.B. Elsevier 2008 CURRENT APPLIED PHYSICS Vol.8 No.6

ZnO nanocombs have been fabricated in high yield via a thermal evaporation process on Si(111) substrate by using metallic zinc powder and oxygen as source materials for zinc and oxygen, respectively, without the use of catalyst or additives at low-temperature. Morphological investigations revealed that the nanocombs were grown in high density over the whole substrate surface. The branches (teeth) of the nanocombs are uniform and nicely attached along one side of the ribbon-like stem and are arranged in a proper manner. X-ray diffraction patterns confirmed that the grown nanostructures were single-crystalline and possessed a wurtzite hexagonal phase. Room-temperature photoluminescence (PL) spectrum of the grown nanostructures is exhibit a dominant, sharp and strong UV emission with a suppressed deep-level emission indicating good crystallinity and optical properties for the as-grown ZnO nanocombs.

Optical and electrical properties of ZnO nanowires grown on aluminium foil by non-catalytic thermal evaporation

Umar, Ahmad,Kim, Byoung-Kye,Kim, Ju-Jin,Hahn, Y B IOP Pub 2007 Nanotechnology Vol.18 No.17

<P>Well-crystallized ZnO nanowires were grown in large quantity on aluminium foil, by a non-catalytic thermal evaporation method using metallic zinc powder in the presence of oxygen at low temperature. Detailed structural and optical characterizations confirmed that the as-grown nanowires were highly crystalline, possessed a wurtzite hexagonal phase, had grown along the <I>c</I>-axis direction and exhibited excellent optical properties. The electrical characteristics of an individual nanowire were observed in air and vacuum by fabricating field-effect transistor (FET) devices. The transistors turned on typically between −5 and 0 V in ambient air. However, a large threshold voltage (<I>V</I><SUB>th</SUB>) shift, ∼5 V, towards negative gate bias was observed in high vacuum. The shift of <I>V</I><SUB>th</SUB> is believed to be related to the charge transfer from the ZnO nanowire surface to the physically adsorbed OH or oxygen. Moreover, the fabricated FETs show a high conductivity ON/OFF ratio of about ∼10<SUP>2</SUP> with ultraviolet (UV) light and hence provide an effective way to use these devices in nanoscale UV detectors and optoelectronic switches. </P>

Ultraviolet-emitting javelin-like ZnO nanorods by thermal evaporation: Growth mechanism, structural and optical properties

Umar, A.,Kim, S.H.,Suh, E.K.,Hahn, Y.B. North Holland ; Elsevier Science Ltd 2007 Chemical physics letters Vol.440 No.1

Highly crystalline aligned javelin-like ZnO nanorods have been synthesized, for the first time, by thermal evaporation method. The as-grown nanorods have been made by the assembling of two pieces of ZnO nanorods, i.e. hexagonal-shaped nanorods and inverted nanocones which are connected to each other in such a manner that the shaft of the nanocones is attached to the upper portion of the hexagonal nanorod and forms a javelin-like ZnO nanorod. Most importantly, the as-grown nanorods exhibit only a sharp and strong UV emission at 381nm, confirming an excellent optical property and showing excellent photoluminescent application potential.

Growth and optical properties of large-quantity single-crystalline ZnO rods by thermal evaporation

Umar, Ahmad,Suh, E K,Hahn, Yoon-Bong Institute of Physics [etc.] 2007 Journal of Physics. D, Applied Physics Vol.40 No.11

<P>Large-quantity synthesis of single-crystalline perfectly hexagonal-shaped ZnO rods has been achieved through the thermal evaporation of metallic zinc powder in the presence of oxygen without the use of metal catalyst or additives. Detailed structural analyses confirm that the structures formed exhibit a wurtzite hexagonal phase and are preferentially oriented along the <I>c</I>-axis direction. Low-temperature photoluminescence shows that the exciton emission bound-to-neutral donor (D<SUP>0</SUP>X) and free-exciton dominate the edge emission region while the donor–acceptor pair (DAP) and its replica dominate the lower energy regions. With increased temperature, D<SUP>0</SUP>X decreases abruptly and is then suppressed, but with further increase in temperature (>100 K) the photoluminescence spectra are dominated by the DAP.</P>

A Centralized e-pedigree system for Agriculture Food Distribution Network

Umar Farooq,Ganjar Alfian,M. Alex Syaekhoni,HyeJung Ahn,Jongtae Rhee 한국경영과학회 2014 한국경영과학회 학술대회논문집 Vol.2014 No.5

Food quality and safety has attained the considerable attention, because of the consumers increasing health awareness, improved economic standards and lifestyle of modern societies. Thus, it is important for distributors, retailers and consumers to purchase agriculture food products and track that they have come through the legal and safe distribution channels. In this paper we proposed a Centralized EPCIS and Sensor Data Repositories based e-pedigree system for agriculture food products to guarantee the quality, safety and reliability of agriculture food products for final consumers. This system not only assure the authenticity of the agriculture food products but also assure the food quality through environmental information such as temperature and humidity during storage, distribution and transportation for food quality.

Aggregation Behavior of Oppositely Charged Gold Nanorods in Aqueous Solution

Umar, Aminah,Choi, Sung-Min American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.22

<P>The aggregation behavior of oppositely charged gold nanorods (GNRs) in aqueous solution has been investigated by zeta potential, UV–vis–NIR, DLS, and TEM measurements. The positively charged GNRs (p-GNRs) and negatively charged GNRs (n-GNRs) were prepared by layer-by-layer deposition of oppositely charged electrolytes on GNR surface. As p-GNRs are added into n-GNR solution (before reaching the isoelectric point), p-GNR/n-GNR aggregations of fairly constant size are formed with the minor component (p-GNRs) mostly at the center and the majority component (n-GNRs) at the outside. While the overall packing of the GNR aggregates is rather random, the local arrangements of GNRs show both side-by-side and end-to-end arrangements, resulting in elongated aggregates due to the anisotropic nature of GNRs. While no precipitation occurs before isoelectric point, the size of aggregates grows rapidly as the isotropic point is approached and rapid precipitation occurs at the isoelectric point, showing ionic-like behavior. Beyond the isoelectric point, partial dissolution of aggregates occurs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-22/jp3102095/production/images/medium/jp-2012-102095_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp3102095'>ACS Electronic Supporting Info</A></P>

HOW TO DEAL WITH RADIO ASTRONOMY INTERFERENCE

UMAR, ROSLAN,HAZMIN, SABRI NOR,ABIDIN, ZAMRI ZAINAL,IBRAHIM, ZAINOL ABIDIN The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

Radio sources are very weak, as they can travel through large distances. Radio sources also have photons with low energies compared to others electromagnetic waves (EM). Microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and the most energetic electromagnetic wave is gamma-rays. Radio astronomy studies are restricted due to radio frequency interference (RFI) produced by people. If this disturbance is not minimized, it poses critical problems for astrophysical studies. The purpose of this paper is to profile RFI maps in Peninsular Malaysia with a minimum mapping technique for RFI interference. Decision-making processes using GIS (Geographical Information System) for the selection requires gathering information for a variety of parameters. These factors affecting the selection process are also taken into account. In this study, various factors or parameters are involved, such as the availability of telecommunications transmission (including radio and television), rainfall, water lines and human activity. This mapping step must be followed by RFI site testing in order to identify areas of low RFI. This study will benefit radio astronomy research, especially regarding the RFI profile.