Ali Hamieh

Bio: Ali Hamieh is an academic researcher from King Abdullah University of Science and Technology. The author has contributed to research in topics: Alkane metathesis & Wireless ad hoc network. The author has an hindex of 12, co-authored 26 publications receiving 430 citations. Previous affiliations of Ali Hamieh include Lebanese University & Rutgers University.

Detection of Radio Interference Attacks in VANET

Abstract: Due to their nature, Vehicular Ad hoc NETwork (VANET) is vulnerable to Denial of Service (DoS) attacks, such as jamming attack. The objective of a jammer is to interfere with legitimate wireless communications, and to degrade the overall QoS of the network. In this paper, we propose a model to detect a particular class of Jamming attack, in which the jammer transmits only when valid radio activity is signaled from its radio hardware. This detection model is based upon the measurement of error distribution.

Detection of Jamming Attacks in Wireless Ad Hoc Networks Using Error Distribution

Abstract: Mobile ad hoc networks are a new wireless networking paradigm for mobile hosts. Unlike traditional mobile wireless networks, ad hoc networks do not rely on any fixed infrastructure. Instead, hosts rely on each other to keep the network connected. The military tactical and other security-sensitive operations are still the main applications of ad hoc networks. One main challenge in design of these networks is their vulnerability to Denial-of-Service (DoS) attacks. In this paper, we consider a particular class of DoS attacks called Jamming. The objective of a jammer is to interfere with legitimate wireless communications. A jammer can achieve this goal by either preventing a real traffic source from sending out a packet, or by preventing the reception of legitimate packets. We propose in this study a new method of detection of such attack by the measurement of error distribution.

Alkane Metathesis with the Tantalum Methylidene [( SiO)Ta(=CH2)Me-2]/[( SiO)(2)Ta(=CH2)Me] Generated from Well-Defined Surface Organometallic Complex [( SiO)(TaMe4)-Me-V]

Abstract: By grafting TaMe5 on Aerosil(700), a stable, well-defined, silica-supported tetramethyl tantalum(V) complex, [( SiO)TaMe4], is obtained on the silica surface After thermal treatment at 150 degrees C, the complex is transformed into two surface tantalum methylidenes, [( SiO)(2)Ta(-CH2)Me] and [( SiO)Ta(-CH2)Me-2], which are active in alkane metathesis and comparable to the previously reported [( SiO)(2)TaHx] Here we present the first experimental study to isolate and identify a surface tantalum carbene as the intermediate in alkane metathesis A systematic experimental study reveals a new reasonable pathway for this reaction

Well-Defined Surface Species [(≡Si—O—)W(═O)Me3] Prepared by Direct Methylation of [(≡Si—O—)W(═O)Cl3], a Catalyst for Cycloalkane Metathesis and Transformation of Ethylene to Propylene

Abstract: The silica-supported tungsten oxo-trimethyl complex [(≡Si—O—)W(═O)Me3] was synthesized using a novel SOMC synthetic approach. By grafting the inexpensive stable compound WOCl4 on the surface of silica, partially dehydroxylated at 700 °C (SiO2-700), a well-defined monopodal surface complex [(≡Si—O—)W(═O)Cl3] was produced. The supported complex directly methylated with ZnMe2 and transformed into [(≡Si—O—)W(═O)Me3], which we fully characterized by microanalysis, IR, mass balance and SS NMR (1H, 13C, 1H–13C HETCOR, 1H–1H DQ and TQ). [(≡Si—O)W(═O)Me3] has two conformational isomers on the surface at room temperature. The conversion of one to the other was observed at 318 K by variable-temperature 13C CP/MAS and 1H spin echo MAS solid-state NMR; this was also confirmed by NMR and DFT calculations. [(≡Si—O)W(═O)Me3] was found to be active in cyclooctane metathesis and to have a wide distribution range in ring-contracted and ring-expanded products. In addition, [(≡Si—O)W(═O)Me3] proved to be highly active for sel...

Synergy between Two Metal Catalysts: A Highly Active Silica-Supported Bimetallic W/Zr Catalyst for Metathesis of n-Decane

Abstract: A well-defined, silica-supported bimetallic precatalyst [≡Si–O–W(Me)5≡Si–O–Zr(Np)3] (4) has been synthesized for the first time by successively grafting two organometallic complexes [W(Me)6 (1) followed by ZrNp4 (2)] on a single silica support. Surprisingly, multiple-quantum NMR characterization demonstrates that W and Zr species are in close proximity to each other. Hydrogenation of this bimetallic catalyst at room temperature showed the easy formation of zirconium hydride, probably facilitated by tungsten hydride which was formed at this temperature. This bimetallic W/Zr hydride precatalyst proved to be more efficient (TON = 1436) than the monometallic W hydride (TON = 650) in the metathesis of n-decane at 150 °C. This synergy between Zr and W suggests that the slow step of alkane metathesis is the C–H bond activation that occurs on Zr. The produced olefin resulting from a β-H elimination undergoes easy metathesis on W.

Advances in One-Pot Synthesis through Borrowing Hydrogen Catalysis

Abstract: The borrowing hydrogen (BH) principle, also called hydrogen auto-transfer, is a powerful approach which combines transfer hydrogenation (avoiding the direct use of molecular hydrogen) with one or more intermediate reactions to synthesize more complex molecules without the need for tedious separation or isolation processes. The strategy which usually relies on three steps, (i) dehydrogenation, (ii) intermediate reaction, and (iii) hydrogenation, is an excellent and well-recognized process from the synthetic, economic, and environmental point of view. In this context, the objective of the present review is to give a global overview on the topic starting from those contributions published prior to the emergence of the BH concept to the most recent and current research under the term of BH catalysis. Two main subareas of the topic (homogeneous and heterogeneous catalysis) have been identified, from which three subheadings based on the source of the electrophile (alkanes, alcohols, and amines) have been consid...

Surface Organometallic and Coordination Chemistry toward Single-Site Heterogeneous Catalysts: Strategies, Methods, Structures, and Activities

Abstract: Site Heterogeneous Catalysts: Strategies, Methods, Structures, and Activities Christophe Copeŕet,*,† Aleix Comas-Vives,† Matthew P. Conley,† Deven P. Estes,† Alexey Fedorov,† Victor Mougel,† Haruki Nagae,†,‡ Francisco Nuñ́ez-Zarur,† and Pavel A. Zhizhko†,§ †Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1−5, CH-8093 Zürich, Switzerland ‡Department of Chemistry, Graduate School of Engineering Science, Osaka University, CREST, Toyonaka, Osaka 560-8531, Japan A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str. 28, 119991 Moscow, Russia

Single-Atom Catalysts across the Periodic Table.

Abstract: Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.

Catalytic Strategies for the Cycloaddition of Pure, Diluted, and Waste CO2 to Epoxides under Ambient Conditions

Abstract: Cyclic organic carbonates represent a relevant class of chemicals that can be prepared from CO2 by cycloaddition to epoxides. The application of efficient catalysts is crucial in allowing the cycloaddition reaction to proceed under very mild conditions of temperature, pressure, and CO2 concentration, thus resulting in a sustainable and carbon-balanced approach to CO2 conversion. This is particularly the case if impure waste CO2 could be employed as a feedstock. In this Review, we have critically analyzed the burgeoning literature on the cycloaddition of CO2 to epoxides with the aim to provide state-of-the-art knowledge on the catalysts that can convert CO2 to carbonates under ambient conditions. These have been systematically organized in families of compounds and critically scrutinized in terms of catalytic activity, availability and mechanistic features. Finally, we provide an overview on the catalytic systems able to function using diluted and impure CO2 as a feedstock.