Radioactively driven colloids: A special case of anomalous diffusion

Citation: Wilson, G., Bahadori, A. A., & Bindra, H. (2019). Radioactively driven colloids: A special case of anomalous diffusion. Journal of Applied Physics, 126(12), 124308. https://doi.org/10.1063/1.5116220A novel concept of self-propelled, radioactively driven colloids is introduced. The focus of this paper is on assessing the impact of alpha emissions on colloidal kinematics. Using Langevin dynamics and a random walk model, a theory has been developed to describe this motion. This theory shows a special case of anomalous diffusion. Numerical simulations have substantiated the theory. It is shown that alpha-particle emission can significantly affect the motion of colloidal particles, although a very short-lived radioisotope is required

Device-to-Device Communications in the Millimeter Wave Band: A Novel Distributed Mechanism

In spite of its potential advantages, the large-scale implementation of the device-to-device (D2D) communications has yet to be realized, mainly due to severe interference and lack of enough bandwidth in the microwave ($\mu$W) band. Recently, exploiting the millimeter wave (mmW) band for D2D communications has attracted considerable attention as a potential solution to these challenges. However, its severe sensitivity to blockage along with its directional nature make the utilization of the mmW band a challenging task as it requires line-of-sight (LOS) link detection and careful beam alignment between the D2D transceivers. In this paper, we propose a novel distributed mechanism which enables the D2D devices to discover unblocked LOS links for the mmW band communication. Moreover, as such LOS links are not always available, the proposed mechanism allows the D2D devices to switch to the $\mu$W band if necessary. In addition, the proposed mechanism detects the direction of the LOS links to perform the beam alignment. We have used tools from stochastic geometry to evaluate the performance of the proposed mechanism in terms of the signal-to-interference-plus-noise ratio (SINR) coverage probability. The performance of the proposed algorithm is then compared to the one of the single band (i.e., $\mu$W/mmW) communication. The simulation results show that the proposed mechanism considerably outperforms the single band communication.Comment: 6 Pages, 6 Figures, Accepted for presentation in Wireless Telecommunication Symposium (WTS'18

Combustion of Gaseous Fuels Under Reduced-Gravity Conditions

The need for an improved understanding of fires is becoming critically important with increased space travel and utilization. While the control of fires in low-gravity environments is not well understood, it is known that buoyancy significantly affects flame behavior and characteristics. The objective of this research is to gain a more fundamental understanding of fires, and to quantify flame behavior under reduced-gravity levels. Non-premixed flames of gaseous fuels are considered in this study because they are relatively simple and easy to control, yet embody mechanisms found in all types of combustion processes ranging from uncontrolled fires to practical combustion systems. This paper presents some recent results from microgravity studies of these flames. In addition, the potential usefulness of lunar- and Martian-based laboratories is discussed in order to understand the characteristics and behavior of fires in reduced-gravity environments

A simple mathematical predictive tool for estimation of a hydrate inhibitor injection rate

Formiranje hidrata u proizvodnji, postrojenjima za obradu i cjevovodima je problem koji industriju prirodnoga plina stoji milijune dolara. Stoga je shvaćanje početka nastanka hidrata nužno za prevladavanje problema hidrata. Cilj prvog koraka ove studije je razvitak korelacije, jednostavne za korištenje, za predviđanje uvjeta za nastajanje hidrata "slatkih" prirodnih plinova.. Ta jednostavna korelacija predviđa tlak nastajanja hidrata "slatkih" prirodnih plinova za tlak do 400 bara (40 000 kPa) i temperature između 13,15 °C i 24,85 °C (260 K i 298 K), kao i molne mase u rasponu od 16 do 29. U slijedećem koraku razvijene su nove empirijske korelacije radi predviđanja potrebnog masenog postotka mono etilen glikola (MEG) u obogaćenim otopinama i količine protjecanja u jedinici vremena za željeno snižavanje temperature formiranja plinskog hidrata. Ove korelacije su napravljene za prirodni plin relativne gustoće 0.6 kod tlaka od 3, 5, 7 i 9 MPa (30, 50, 70 i 90 bara) koji su primjenjivi za masni prirodni plin temperature od 20, 30, 40 i 50 °C. Kako bi se proširila primjenjivost ovih korelacija na širi spektar mješavina prirodnoga plina relativne gustoće do 0,8, dana su dva poopćena korekcijska faktora. Točnost ove jednostavne metode uspoređena je s rezultatima simulacije dobivenim korištenjem komercijalnoga softwarea pri čemu se je pokazala izuzetna podudarnost. U svim slučajevima postotak pogreške iznosio je približno 2% i 5% za predviđanje pada temperature formiranja hidrata i obroka utiskivanja mono etilen glikola (MEG). Jednadžbe koje su razvijene u ovoj studiji mogu biti od značajne praktičke važnosti za inženjere i znanstvenike za brzu provjeru uvjeta formiranja hidrata prirodnih plinova s ili bez prisustva inhibitora bez potrebe za primjenom bilo kakvih eksperimentalnih mjerenja. Kemijski i procesni inženjeri će ustanoviti da su jednostavne jednadžbe prilagođene korisniku s jasnim izračunima bez složenih izraza.The formation of hydrates in production, processing facilities and pipelines has been a problem to the natural gas industry, that cost several millions of dollars.. Therefore, an understanding of the inception of hydrate formation is necessary to overcoming hydrate problems. The aim of the first step of this study is to develop a simple-to-use correlation for predicting hydrate-forming conditions of sweet natural gases. This simple correlation estimates hydrate formation pressure of sweet natural gases for pressures up to 40 000 kPa and temperatures between 260 K and 298 K as well as molecular weights in the range of 16 to 29. In the next step, novel empirical correlations are developed to predict the required MEG weight percent in the rich solution and the flow-rate for desired depression of the gas hydrate formation temperature. These correlations are generated for a natural gas with relative density of 0.6 at pressures of 3, 5, 7, and 9 MPa, which are applicable to wet gas temperatures of 20, 30, 40, and 50 °C. In order to extend the application of these correlations to wide ranges of natural gas mixtures with specific gravities of up to 0.8, two generalized correction factors are also provided. The accuracy of this simple method is compared with the simulation results obtained by commercial software which showed excellent agreement. In all cases the error percent was approximately 2% and 5% for predicting hydrate formation temperature depression and MEG injection rate, respectively. The fitted equations developed in this study can be of immense practical value for the engineers and scientists to have a quick check on hydrate formation condition of natural gases with or without presence of inhibitor without opting for any experimental measurements. In particular, chemical and process engineers would find the simple equations to be user-friendly with transparent calculations involving no complex expressions

Development of a Solar Town in Iran

Iran's rapid industrialization progress has necessitated the development of cities and townships adjacent to the industrial complexes. The source of energy for these townships is similar to the rest of the country, and it is basically oil and natural gas. Iran is a country rich in oil, natural gas, and solar energy, and the life style of its people -- especially the majority of those drawn to these industrial towns -- is not highly energy dependent. To save on fossil fuel consumption, the country has already launched the programs to utilize other sources of energy, namely nuclear, geothermal, and solar. Development of a solar town whose total energy requirements for heating, cooling, cooking, communication, local transportation, etc., are met by solar energy, sky radiation, and other similar sources, is suggested for the first time and is a plan which can have a long-range fuel saving and ecological significance. In this solar community no hydrocarbon fuels, except for those produced through sewage and agricultural waste conversions, are to be used

Energy Sources and Uses in Iran: A Brief Review

A thorough study of the energy sources and uses in Iran is rather difficult due to the lack of accurate statistical data. The information provided by many sources do not always agree with each other and are often incomplete. In making this study, the information available were employed to construct the tables, but primarily the data that seemed to be most consistent and most complete were used to plot the curves. A more complete study of the energy picture in Iran requires much more time than was available to the writer and requires a thorough examination of the many reports and information published by the governmental and private organizations over the past several years. In this paper, background information on the geography and people are given first, followed by a brief description of energy sources and uses

Physical Layer Modeling and Optimization of Silicon Photonic Interconnection Networks

The progressive blooming of silicon photonics technology (SiP) has indicated that optical interconnects may substitute the electrical wires for data movement over short distances in the future. Silicon Photonics platform has been the subject of intensive research for more than a decade now and its prospects continue to emerge as it enjoys the maturity of CMOS manufacturing industry. SiP foundries all over the world and particularly in the US (AIM Photonics) have been developing reliable photonic design kits (PDKs) that include fundamental SiP building blocks such as wavelength selective modulators and tunable filters. Microring resonators (MRR) are hailed as the most compact devices that can perform both modulation and demodulation in a wavelength division multiplexed (WDM) transceiver design. Although the use of WDM can reduce the number of fibers carrying data, it also makes the design of transceivers challenging. It is probably acceptable to achieve compactness at the expense of somewhat higher transceiver cost and power consumption. Nevertheless, these two metrics should remain close to their roadmap values for Datacom applications. An increase of an order of magnitude is clearly not acceptable. For example costs relative to bandwidth for an optical link in a data center interconnect will have to decrease from the current $5/Gbps down to <$1/Gbps. Additionally, the transceiver itself must remain compact. The optical properties of SiP devices are subject to various design considerations, operation conditions, and optimization procedures. In this thesis, the general goal is to develop mathematical models that can accurately describe the thermo-optical and electro-optical behavior of individual SiP devices and then use these models to perform optimization on the parameters of such devices to maximize the capabilities of photonic links or photonic switch fabrics for datacom applications. In Chapter 1, Introduction, we first provide an overview of the current state of the optical transceivers for data centers and datacom applications. Four main categories for optical interfaces (Pluggable transceivers, On-board optics, Co-packaged optics, monolithic integration) are briefly discussed. The structure of a silicon photonic link is also briefly introduced. Then the direction is shifted towards optical switching technologies where various technologies such as free space MEMS, liquid crystal on silicon (LCOS), SOA-based switches, and silicon-based switches are explored. In Chapter 2, Silicon Photonic Waveguides, we present an extensive study of the silicon-on-insulator (SOI) waveguides that are the basic building blocks of all of the SiP devices. The dispersion of Si and SiO2 is modeled with Sellmiere equation for the wavelength range 1500–1600 nm and then is used to calculate the TE and TM modes of a 2D slab waveguide. There are two reasons that 2D waveguides are studied: first, the modes of these waveguides have closed form solutions and the modes of 3D waveguides can be approximated from 2D waveguides based on the effective index method. Second, when the coupling of waveguides is studied and the concept of curvature function of coupling is developed, the coupled modes of 2D waveguides are used to show that this approach has some inherent small error due to the discretization of the nonuniform coupling. This chapter finishes by describing the coefficients of the sensitivity of optical modes of the waveguides to the geometrical and material parameters. Perturbation theory is briefly presented as a way to analytically examine the impact of small perturbations on the effective index of the modes. In Chapter 3, Compact Modeling Approach, the concept of scattering matrix of a multi-port silicon photonic device is presented. The elements of the S-matrix are complex numbers that relate the amplitude and phase relationships of the optical models in the input and output ports. Based on the scattering matrix modeling of silicon photonics devices, two methods of solving photonic circuits are developed: the first one is based on the iteration for linear circuits. The second approach is based on the construction of an equivalent signal flow graph (SFG) for the circuit. We show that the SFG approach is very efficient for circuits involving microring resonator structures. Not only SFG can provide the solution for the transmission, it also provides the signal paths and the closed-form solution based on the Mason’s graph formula. We also show how the SFG method can be utilized to formulate the backscattering effects inside a ring resonator. In Chapter 4, Scalability of Silicon Photonic Switch Fabrics, we develop the models for electro-optic Mach-Zehnder switch elements (2×2). For the electro-optic properties, the empirical Soref’s equations are used to characterize how the loss and index of silicon changes when the charge carrier density is changed. We then use our photonic circuit solver based on the iteration method to find accurate result of light propagation in large-scale switch topologies (e.g. 4×4, and 8×8). The concept of advanced path mapping based on physical layer evaluation of the switch fabric is introduced and used to develop the optimum routing tables for 4×4 and 8×8 Benes switch topologies. In Chapter 5, Design space of Microring Resonators, we introduce the concept of curvature function of coupling to mathematically characterize the coupling coefficient of a ring resonator to a waveguide as a function of the geometrical parameters (ring radius, coupling gap, width and height of waveguides) and the wavelength. Extensive 2D and 3D FDTD simulations are carried out to validate our modeling approach. Experimental demonstrations are also used to not only further validate our modeling of coupling, but also to extract an empirical power-law model for the bending loss of the ring resonators as a function the radius. By combining these models, we for the first time present a full characterization of the design space of microring resonators. Moreover, the value of this discussion will be further apparent when the scalability of a silicon photonic link is studied. We will show that the FSR of the rings determines the optical bandwidth but it also impacts the properties of the ring resonators. In Chapter 6, Thermo-optic Efficiency of Microheaters, we develop analytical models for the thermo-optic properties of SiP waveguides. For the thermo-optic properties, the concept of thermal impulse response is mathematically developed for integrated micro-heaters. The thermal impulse response is a key function that determines the tradeoff between heating efficiency and heating speed (thermal bandwidth), as well as allows us to predict the pulse-width-modulation (PWM) optical response of the heater-waveguide system. One of the motivations behind this study was to find the highest possible efficiency for thermal tuning of microring resonators to use it in the evaluation of the energy consumption of a photonic link. The results indicate 2 nm/mW which is in agreement with the trends that we see in the literature. In Chapter 7, Crosstalk Penalty, we theoretically and experimentally investigate the optical crosstalk effects in microring-based silicon photonic interconnects. Both inter-channel crosstalk and intra-channel crosstalk are investigated and approximate equations are developed for their corresponding power penalties. Inclusion of the inter-channel crosstalk is an important part of our final analysis of a silicon photonic link. In Chapter 8, Scalability of Silicon Photonic Links, we present the analysis of a WDM silicon photonics point-to-point link based on microring modulators and microring wavelength filters. Our approach is based on the power penalty analysis of non-return-to-zero (NRZ) signals and Gaussian noise statistics. All the necessary equations for the optical power penalty calculations are presented for microring modulators and filters. The first part of the analysis is based on various ideal assumptions which lead to a maximum capacity of 2.1 Tb/s for the link. The second part of the analysis is carried out with more realistic assumptions on the photonic elements in the link, culminating in a maximum throughput of 800 Gb/s. We also provide estimations of the energy/bit metric of such links based on the optimized models of electronic circuits in 65 nm CMOS technology

Die 100 größten Unternehmen in Hessen

2. Auflage der "100 größten Unternehmen in Hessen": Jede Region hat ihre Besonderheiten und „Leuchttürme“. Zumeist spielen dabei große Unternehmen eine entscheidende Rolle, denn sie sind häufig Kristallisationspunkte für den Mittelstand. Die Landesbank Hessen-Thüringen und die Hessen Agentur haben diese Schrittmacher für Hessen identifiziert. Sie veröffentlichen zum zweiten Mal die Rangliste der 100 größten Unternehmen in Hessen (1. Auflage 2005). Beschäftigte als Maßstab: Um die Bedeutung der Unternehmen in und für Hessen zu messen, wurde nur auf die Mitarbeiter abgestellt, die an den hessischen Standorten der Firmen beschäftigt waren. Die gewählte Messgröße „hessische Beschäftigte“ sorgte zudem in der später folgenden Unternehmensbefragung für eine hohe Antwortbereitschaft. Hohe Konzentration: Insgesamt arbeiten rund 485.000 Beschäftigte bei den 100 größten Unternehmen in Hessen. Das sind 16 % der hessischen Erwerbstätigen. Dabei konzentrieren sich die Arbeitnehmer auf die zehn größten Unternehmen: Rund 40 % der im Ranking erfassten Mitarbeiter sind bei ihnen angestellt. Die ersten 50 Unternehmen sind die Arbeitgeber für 80 % der Beschäftigten. Wirtschaftliches Umfeld steinig: Das weltwirtschaftliche Umfeld ist für die Großunternehmen steinig: Insgesamt ist 2009 mit einem Rückgang des realen BIP (nicht arbeitstäglich bereinigt) von 2,6 % in Deutschland zu rechnen. Hessen wird aufgrund des Finanz- und Logistiksektors eine höhere Abnahme (-3 %) zu schultern haben, wie auch schon im Rezessionsjahr 2002. Dennoch flackert schon zaghaftes Licht am Ende des Tunnels: Die umfangreichen Konjunkturpakete sollten ihre Adressaten, die Produzenten und Konsumenten, erreichen und damit in der zweiten Jahreshälfte beginnen, der Rezession entgegenzuwirken. Logistik wichtig für Hessen: Logistikunternehmen sind unter den 100 größten Unternehmen in Hessen überdurchschnittlich häufig vertreten: 26 % der Beschäftigten aller befragten Firmen arbeiten bei Logistikunternehmen. Durch die Weiterentwicklung von Logistikstandorten eröffnen sich Chancen für die breite Arbeitnehmerschaft, da die Logistikbranche auf allen Qualifikationsebenen Arbeitsplätze bietet. Sie kann damit das Arbeitsplatzangebot einer Region sinnvoll ergänzen. Im Gegensatz zu der derzeitig konjunkturell schwierigen Lage sind die langfristigen Perspektiven für den Güter- und Personenverkehr nach Prognosen des IFEU Heidelberg (Institut für Energie- und Umweltforschung) äußerst positiv. Das mittelfristige Wachstum wird nicht mit den bisherigen Kapazitäten zu realisieren sein. Offensichtlicher Ansatzpunkt ist hier in Hessen der Infrastrukturausbau im Bereich Flughafen und Straße. Gleichberechtigt dazu sollte aber auch intensiv geforscht werden, denn Forschung stiftet neben dem unmittelbaren Nutzen für die Unternehmen in der Region auch eine Verbesserung der Standortqualität