Note: This page contains sample records for the topic ammonia recycle percolation from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Pretreatment of lignocellulosic biomass by autohydrolysis and aqueous ammonia percolation  

Microsoft Academic Search

A two-stage biomass pretreatment process-a combination of autohydrolysis and aqueous ammonia percolation-was experimentally\\u000a studied as a method to remove and recover hemicellulose from lignocellulosic biomass. Hemicellulose was completely separated\\u000a from the biomass after 1 hr of autohydrolysis at 200‡C. As reaction temperature and\\/or time of autohydrolysis was increased\\u000a in the range of 170-200‡C and 1–2.5 hr, respectively, the amount of

Hyon Hee Yoon

1998-01-01

2

Ammonia recycling enables sustainable operation of bioelectrochemical systems.  

PubMed

Ammonium (NH4(+)) migration across a cation exchange membrane is commonly observed during the operation of bioelectrochemical systems (BES). This often leads to anolyte acidification (pH <5.5) and complete inactivation of biofilm electroactivity. Without using conventional pH controls (dosage of alkali or pH buffers), the present study revealed that anodic biofilm activity (current) could be sustained if recycling of ammonia (NH3) was implemented. A simple gas-exchange apparatus was designed to enable continuous recycling of NH3 (released from the catholyte at pH >10) from the cathodic headspace to the acidified anolyte. Results indicated that current (110 mA or 688 Am(-3) net anodic chamber volume) was sustained as long as the NH3 recycling path was enabled, facilitating continuous anolyte neutralization with the recycled NH3. Since the microbial current enabled NH4(+) migration against a strong concentration gradient (~10-fold), a novel way of ammonia recovery from wastewaters could be envisaged. PMID:23774293

Cheng, Ka Yu; Kaksonen, Anna H; Cord-Ruwisch, Ralf

2013-09-01

3

Isolation of high quality lignin as a by-product from ammonia percolation pretreatment of poplar wood.  

PubMed

A two-step process combining percolation-mode ammonia pretreatment of poplar sawdust with mild organosolv purification of the extracted lignin produced high quality, high purity lignin in up to 31% yield and 50% recovery. The uncondensed fraction of the isolated lignin was up to 34%, close to that the native lignin (40%). Less lignin was recovered after pretreatment in batch mode, apparently due to condensation during the longer residence time of the solubilised lignin at elevated temperature. The lignin recovery was directly correlated with its molecular weight and its nitrogen content. Low nitrogen incorporation, observed at high ammonia concentration, may be explained by limited homolytic cleavage of ?-O-4 bonds. Ammonia concentrations from 15% to 25% (w/w) gave similar results in terms of lignin structure, yield and recovery. PMID:24755321

Bouxin, Florent P; David Jackson, S; Jarvis, Michael C

2014-06-01

4

Improved methane fermentation of chicken manure via ammonia removal by biogas recycle.  

PubMed

This study demonstrates methane fermentation that was carried out along with ammonia striping to avoid ammonia accumulation that significantly inhibited methane production. Ammonia was successfully removed by means of recycling of biogas followed by gas washing in sulfuric acid to capture ammonia, when chicken manure was anaerobically digested for 4 days at 55 degrees C and at an initial pH of 8-9. By using this method, 80% of total nitrogen in chicken manure was converted to ammonia and 82% of the produced ammonia was removed. A bench scale reactor equipped with an ammonia-stripping unit for methane production from chicken manure was developed and operated in repeated batch mode. At an initial pH of 8 and at 55 degrees C, 195 and 157 ml g-VS(-1) of methane was successfully produced from the treated chicken manure and the mixture of treated chicken manure and raw chicken manure in the ratio of 1:1, respectively. In this method, ammonia concentration was maintained at a level lower than 2g-N kg-wet sludge(-1) in the reactor. PMID:20378337

Abouelenien, Fatma; Fujiwara, Wataru; Namba, Yuzaburo; Kosseva, Maria; Nishio, Naomichi; Nakashimada, Yutaka

2010-08-01

5

Recycled aqueous ammonia expansion (RAAE) pretreatment to improve enzymatic digestibility of corn stalks.  

PubMed

A novel lignocellulose pretreatment method using aqueous ammonia for biofuel production was proposed in this study, which named recycled aqueous ammonia expansion (RAAE). Effects of temperature, pretreatment time, water to dry corn stalks loading and flow rate of aqueous ammonia on substrate enzymatic digestibility and sugar yield were investigated. Pretreatment temperature and time are important factors that affect RAAE process. Recirculation process could improve biomass digestibility and sugar yield compared with batch experiment. After RAAE pretreatment, about 70% of the lignin was removed, while more than 90% of the cellulose was preserved in the solids, the substrate crystallinity also increased because of the removal of amorphous portion. The maximum glucan enzymatic digestibility of pretreated biomass was 85.70%, which was obtained at 85°C, 11 min, 80% water to dry corn stalks loading and 1.5L/min aqueous ammonia flow rate. PMID:23624049

Zhang, Chao; Pang, Feng; Li, Bing; Xue, Shulin; Kang, Yong

2013-06-01

6

Recycling of Aluminum Salt Cake: Utilization of Evolved Ammonia  

NASA Astrophysics Data System (ADS)

The communication presents an extension of the leaching process of the salt cake earlier developed by the present authors. The process describes the investigations in capturing the ammonia gas evolved by hydrolysis of AlN during aqueous leaching at 373 K (100 °C) by CO2-saturated water. The product, i.e., ammonium bicarbonate which is free of chlorides, is a value-added product and can find application in the fertilizer industry. The present method has the added advantage of fixing CO2 as well.

Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri

2013-02-01

7

AMMONIA  

EPA Science Inventory

This document summarizes the available information on ammonia as it relates to its effects on man and his environment. Ammonia is a ubiquitous substance and is known widely as a household cleaning agent and as a fertilizer. It plays an important role in the nitrogen cycle--in the...

8

Sequential hydrolysis of hemicellulose and lignin in lignocellulosic biomass by two-stage percolation process using dilute sulfuric acid and ammonium hydroxide  

Microsoft Academic Search

To obtain the total fractionation and pretreatment of the corn stover, two-stage percolation process was investigated. This\\u000a process consists of two steps: use of 0.07 wt% sulfuric acid for hemicellulose recovery in first stage and ARP (ammonia recycled\\u000a percolation) in the following stage for lignin recovery. Among tested conditions, the best conditions of two-stage process\\u000a were as follows: 1st stage;

Tae Hyun Kim

9

Synthese du Nitrate d'Ammonium a Partir d'Ammoniac et d'Acide Nitrique avec Recuperation et Recyclage de l'Azote Mineral (Recovery and Recycling of Ammonia Contained in Gases from Ammonium Nitrate Production).  

National Technical Information Service (NTIS)

The company performs ammonium nitrate synthesis accompanied by recovery and recycling of the ammonia contained in the vapor. The synthesis of ammonium nitrate is carried out in both techniques through a nitric acid reaction on the ammonia. When the reacti...

1981-01-01

10

Recycling  

NSDL National Science Digital Library

You will be learning all about recycling and asking questions as you learn more about recycling. Afterward, you will be making recycling bins that we will use in our classroom. Click on each of the different links and research about recycling. Find out what recycling is, what can be recycled, and why we should recycle. As you find information, add it to the "describing wheel" that is given to you by Ms. Pollak. Answer the main question: What is recycling? Come ...

sgp0002

2010-03-27

11

Process Modeling of an Advanced NH3 Abatement and Recycling Technology in the Ammonia-Based CO2 Capture Process.  

PubMed

An advanced NH3 abatement and recycling process that makes great use of the waste heat in flue gas was proposed to solve the problems of ammonia slip, NH3 makeup, and flue gas cooling in the ammonia-based CO2 capture process. The rigorous rate-based model, RateFrac in Aspen Plus, was thermodynamically and kinetically validated by experimental data from open literature and CSIRO pilot trials at Munmorah Power Station, Australia, respectively. After a thorough sensitivity analysis and process improvement, the NH3 recycling efficiency reached as high as 99.87%, and the NH3 exhaust concentration was only 15.4 ppmv. Most importantly, the energy consumption of the NH3 abatement and recycling system was only 59.34 kJ/kg CO2 of electricity. The evaluation of mass balance and temperature steady shows that this NH3 recovery process was technically effective and feasible. This process therefore is a promising prospect toward industrial application. PMID:24850444

Li, Kangkang; Yu, Hai; Tade, Moses; Feron, Paul; Yu, Jingwen; Wang, Shujuan

2014-06-17

12

Recycling.  

ERIC Educational Resources Information Center

Discusses the range of benefits resulting from recycling efforts and projects. Presents information and data related to the recycling of metals, cans, paper, fans, and plastics. Suggestions for motivating and involving youth in recycling programs are also offered. (ML)

Sinker, Barbara

1986-01-01

13

Recycling  

NSDL National Science Digital Library

What objects can be recycled? 1. Click on link. Watch video. Recycle Guy Video 2. Click on link. Watch video. Talking Trash Video 3. Click on link. Watch video. Recycling At School Video 4. Click on link. Play game. Star Fall Recycling Game 5. Click on link. Play game. National Geographic Recycling Game 6. Click on link. Ask Ms. Owens how to do it. Things We Recycle Chart 7. Please see Miss Owens for instructions on the following ...

2011-04-07

14

Exergy analysis of industrial ammonia synthesis  

Microsoft Academic Search

Exergy consumption of ammonia production plants depends strongly on the ammonia synthesis loop design. Due to the thermodynamically limited low degree of conversion of hydrogen–nitrogen mixture to ammonia, industrial ammonia synthesis is implemented as recycle process (so-called “ammonia synthesis loop”). Significant quantities of reactants are recycled back to reactor, after the removal of ammonia at low temperatures. Modern ammonia synthesis

Zornitza Kirova-Yordanova

2004-01-01

15

Recycle  

SciTech Connect

;Contents: The Problem; What`s In Our Trash; Where Does Trash Go; Where Does Our Trash Go; The Solution; What Is Recycling; Why Should We Recycle; A National Goal of 25%; What Can We Recycle; What Do We Do With Our Recyclables.

NONE

1988-10-01

16

Desulfurization in reducing atmosphere and ammonia injection denitrification in a coal-fired fluidized bed combustor with fly-ash recycle  

NASA Astrophysics Data System (ADS)

With the rising of IGCC and the second generation PFBC-CC, and with the development of technology of staged combustion to lower emission of NOx, the desulfurization efficiency under reducing atmosphere is raised. In this paper, with the application of the fly-ash recycle and two-stage combustion technologies in a fluidized bed combustor, the desulfurization test under reducing atmosphere is described. Meanwhile, ammonia injection test was also conducted. Results show that desulfurization under reducing atmosphere has higher efficiency, and ammonia injection denitrification effect is very perfect.

Zhong, Zhaoping; Lan, Jixiang; Han, Yongsheng; Wu, Xin; Zheng, Haiyun

1997-03-01

17

Recycling  

NASA Astrophysics Data System (ADS)

Recycling systems are classified into those employing typically three methods, and the progress of each method is described. In mechanical recycling, powders of phenolic materials are recovered via a mechanical process and reused as fillers or additives in virgin materials. The effects to flowability, curability, and mechanical properties of the materials are explained. In feedstock recycling, monomers, oligomers, or oils are recovered via chemical processes and reused as feedstock. Pyrolysis, solvolysis or hydrolysis, and supercritical or subcritical fluid technology will also be introduced. When using a subcritical fluid of phenol, the recycled material maintains excellent properties similar to the virgin material, and a demonstration plant has been constructed to carry out mass production development. In energy recovery, wastes of phenolic materials are used as an alternative solid fuel to coal because they are combustible and have good calorific value. Industrial wastes of these have been in practical use in a cement plant. Finally, it is suggested that the best recycling method should be selected according to the purpose or situation, because every recycling method has both strengths and weaknesses. Therefore, quantitative and objective evaluation methods in recycling are desirable and should be established.

Goto, Junya; Santorelli, Michael

18

Advanced Life Support Water Recycling Technologies Case Studies: Vapor Phase Catalytic Ammonia Removal and Direct Osmotic Concentration  

NASA Technical Reports Server (NTRS)

Design for microgravity has traditionally not been well integrated early on into the development of advanced life support (ALS) technologies. NASA currently has a many ALS technologies that are currently being developed to high technology readiness levels but have not been formally evaluated for microgravity compatibility. Two examples of such technologies are the Vapor Phase Catalytic Ammonia Removal Technology and the Direct Osmotic Concentration Technology. This presentation will cover the design of theses two systems and will identify potential microgravity issues.

Flynn, Michael

2004-01-01

19

Elimination of phenols, ammonia and cyanide in wash water from biomass gasification, and nitrogen recycling using planted trickling filters.  

PubMed

Trickling filters were used to treat wash water from a wood gasifier. This wash water contained toxic substances such as ammonium, cyanide, phenols, and PAH. The goal was to develop a system that degraded toxic substances, and achieved full nitrification of ammonia. A 1 kW model wood gasifier plant delivered wash water for the experiments, which was standardised to a conductivity of 3 mS/cm by dilution. Toxicity was assessed by bacterial luminescence detection, germination test with cress (Lepidium sativum), and pot plants cultivated in a hydroponic setup irrigated continuously with the wastewater. Treatment experiments were done in both planted and unplanted trickling filters. Plant yield was similar to conventional hydroponic production systems. The trickling filters achieved complete detoxification of phenol, PAH and cyanide as well as full nitrification. The specific elimination rates were 100 g m(-3) Leca d(-1) for phenols and 90 g m(-3) Leca d(-1) for ammonium in planted systems. In unplanted trickling filters circulated for 63 h, phenol concentration decreased from 83.5 mg/L to 2.5 mg/L and cyanide concentration from 0.32 mg/L to 0.02 mg/L. PAH concentrations were reduced from 3,050 microg/L to 0.89 microg/L within 68 days. The assays demonstrated the feasibility of using the technique to construct a treatment system in a partially closed circulation for gasifier wash water. The principal advantage is to convert toxic effluents from biomass gasifiers into a non-toxic, nitrogen-rich fertiliser water, enabling subsequent use in plant production and thus income generation. However, the questions of long-term performance and possible accumulation of phenols and heavy metals in the produce still have to be studied. PMID:19955650

Graber, Andreas; Skvarc, Robert; Junge-Berberovi?, Ranka

2009-01-01

20

Substrate Dependency and Effect of Xylanase Supplementation on Enzymatic Hydrolysis of Ammonia-Treated Biomass  

NASA Astrophysics Data System (ADS)

Pretreatment based on aqueous ammonia was investigated under two different modes of operation: soaking in aqueous ammonia and ammonia recycle percolation. These processes were applied to three different feedstocks with varied composition: corn stover, high lignin (HL), and low lignin (LL) hybrid poplars. One of the important features of ammonia-based pretreatment is that most of the hemicellulose is retained after treatment, which simplifies the overall bioconversion process and enhances the conversion efficiency. The pretreatment processes were optimized for these feedstocks, taking carbohydrate retention as well as sugar yield in consideration. The data indicate that hybrid poplar is more difficult to treat than corn stover, thus, requires more severe conditions. On the other hand, hybrid poplar has a beneficial property that it retains most of the hemicellulose after pretreatment. To enhance the digestibility of ammonia-treated poplars, xylanase was supplemented during enzymatic hydrolysis. Because of high retention of hemicellulose in treated hybrid poplar, xylanase supplementation significantly improved xylan as well as glucan digestibility. Of the three feedstocks, best results and highest improvement by xylanase addition was observed with LL hybrid poplar, showing 90% of overall sugar yield.

Gupta, Rajesh; Kim, Tae Hyun; Lee, Yoon Y.

21

STP Percolation Program  

NSDL National Science Digital Library

The STP Percolation program generates occupied lattice sites with probability p and then determines the clusters of occupied sites. The purpose of this program is to demonstrate some of the important properties of percolation, especially near the geometrical phas transition. The default system is a square lattice of linear dimension L=128 and value of p=0.5927 at which the lattice is displayed. STP Percolation is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp_Percolation.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2009-03-09

22

Percolation with Constant Freezing  

NASA Astrophysics Data System (ADS)

We introduce and study a model of percolation with constant freezing (PCF) where edges open at constant rate 1 , and clusters freeze at rate ? independently of their size. Our main result is that the infinite volume process can be constructed on any amenable vertex transitive graph. This is in sharp contrast to models of percolation with freezing previously introduced, where the limit is known not to exist. Our interest is in the study of the percolative properties of the final configuration as a function of ? . We also obtain more precise results in the case of trees. Surprisingly the algebraic exponent for the cluster size depends on the degree, suggesting that there is no lower critical dimension for the model. Moreover, even for ?

Mottram, Edward

2014-04-01

23

Percolation with Constant Freezing  

NASA Astrophysics Data System (ADS)

We introduce and study a model of percolation with constant freezing ( PCF) where edges open at constant rate , and clusters freeze at rate independently of their size. Our main result is that the infinite volume process can be constructed on any amenable vertex transitive graph. This is in sharp contrast to models of percolation with freezing previously introduced, where the limit is known not to exist. Our interest is in the study of the percolative properties of the final configuration as a function of . We also obtain more precise results in the case of trees. Surprisingly the algebraic exponent for the cluster size depends on the degree, suggesting that there is no lower critical dimension for the model. Moreover, even for , it is shown that finite clusters have algebraic tail decay, which is a signature of self organised criticality. Partial results are obtained on , and many open questions are discussed.

Mottram, Edward

2014-06-01

24

Ammonia Process by Pressure Swing Adsorption  

SciTech Connect

The overall objective of the project is to design, develop and demonstrate a technically feasible and commercially viable system to produce ammonia along with recovery of the products by adsorption separation methods and significantly decrease the energy requirement in ammonia production. This is achieved through a significantly more efficient ammonia psa recovery system. The new ammonia recovery system receives the reactor effluents and achieves complete ammonia recovery, (which completely eliminates the energy intensive refrigeration and condensation system currently used in ammonia production). It also recovers the unused reactants and recycles them back to the reactor, free of potential reactor contaminants, and without the need for re-compression and re-heat of recycle stream thereby further saving more energy. The result is a significantly lower energy consumption, along with capital cost savings.

Dr Felix Jegede

2010-12-27

25

Microtransition cascades to percolation.  

PubMed

We report the discovery of a discrete hierarchy of microtransitions occurring in models of continuous and discontinuous percolation. The precursory microtransitions allow us to target almost deterministically the location of the transition point to global connectivity. This extends to the class of intrinsically stochastic processes the possibility to use warning signals anticipating phase transitions in complex systems. PMID:24785054

Chen, Wei; Schröder, Malte; D'Souza, Raissa M; Sornette, Didier; Nagler, Jan

2014-04-18

26

Microtransition Cascades to Percolation  

NASA Astrophysics Data System (ADS)

We report the discovery of a discrete hierarchy of microtransitions occurring in models of continuous and discontinuous percolation. The precursory microtransitions allow us to target almost deterministically the location of the transition point to global connectivity. This extends to the class of intrinsically stochastic processes the possibility to use warning signals anticipating phase transitions in complex systems.

Chen, Wei; Schröder, Malte; D'Souza, Raissa M.; Sornette, Didier; Nagler, Jan

2014-04-01

27

Percolation in Voronoi tilings  

Microsoft Academic Search

We consider a percolation process on a random tiling of Rd into Voronoi cells based on points of a realization of a Poisson process. We prove the existence of a phase transition as the proportion p of open cells is varied and provide relatively close upper and lower bounds for the critical probability pc.

Paul N. Balister; Béla Bollobás; Anthony Quas

2005-01-01

28

Unstable supercritical discontinuous percolation transitions.  

PubMed

The location and nature of the percolation transition in random networks is a subject of intense interest. Recently, a series of graph evolution processes have been introduced that lead to discontinuous percolation transitions where the addition of a single edge causes the size of the largest component to exhibit a significant macroscopic jump in the thermodynamic limit. These processes can have additional exotic behaviors, such as displaying a "Devil's staircase" of discrete jumps in the supercritical regime. Here we investigate whether the location of the largest jump coincides with the percolation threshold for a range of processes, such as Erd?s-Rényipercolation, percolation via edge competition and via growth by overtaking. We find that the largest jump asymptotically occurs at the percolation transition for Erd?s-Rényiand other processes exhibiting global continuity, including models exhibiting an "explosive" transition. However, for percolation processes exhibiting genuine discontinuities, the behavior is substantially richer. In percolation models where the order parameter exhibits a staircase, the largest discontinuity generically does not coincide with the percolation transition. For the generalized Bohman-Frieze-Wormald model, it depends on the model parameter. Distinct parameter regimes well in the supercritical regime feature unstable discontinuous transitions-a novel and unexpected phenomenon in percolation. We thus demonstrate that seemingly and genuinely discontinuous percolation transitions can involve a rich behavior in supercriticality, a regime that has been largely ignored in percolation. PMID:24229160

Chen, Wei; Cheng, Xueqi; Zheng, Zhiming; Chung, Ning Ning; D'Souza, Raissa M; Nagler, Jan

2013-10-01

29

Probabilistic bootstrap percolation  

Microsoft Academic Search

In bootstrap percolation, sites are occupied with probabilityp, but those with less thanm occupied first neighbors are removed. This culling process is repeated until a stable configuration (all occupied sites have at leastm occupied first neighbors or the whole lattice is empty) is achieved. Form?m1 the transition is first order, while formm1 it is second order, withm-dependent exponents. In probabilistic

N. S. Branco

1993-01-01

30

Invasion percolation with memory  

NASA Astrophysics Data System (ADS)

Motivated by the problem of finding the minimum threshold path (MTP) in a lattice of elements with random thresholds ?i, we propose a new class of invasion processes, in which the front advances by minimizing or maximizing the measure Sn=?i?ni for real n. This rule assigns long-time memory to the invasion process. If the rule minimizes Sn (case of minimum penalty), the fronts are stable and connected to invasion percolation in a gradient [J. P. Hulin, E. Clement, C. Baudet, J. F. Gouyet, and M. Rosso, Phys. Rev. Lett. 61, 333 (1988)] but in a correlated lattice, with invasion percolation [D. Wilkinson and J. F. Willemsen, J. Phys. A 16, 3365 (1983)] recovered in the limit \\|n\\|=?. For small n, the MTP is shown to be related to the optimal path of the directed polymer in random media (DPRM) problem [T. Halpin-Healy and Y.-C. Zhang, Phys. Rep. 254, 215 (1995)]. In the large n limit, however, it reduces to the backbone of a mixed site-bond percolation cluster. The algorithm allows for various properties of the MTP and the DPRM to be studied. In the unstable case (case of maximum gain), the front is a self-avoiding random walk.

Kharabaf, Hooshang; Yortsos, Yanis C.

1997-06-01

31

Space-filling percolation.  

PubMed

A region of two-dimensional space has been filled randomly with a large number of growing circular disks allowing only a "slight" overlapping among them just before their growth stops. More specifically, each disk grows from a nucleation center that is selected at a random location within the uncovered region. The growth rate ? is a continuously tunable parameter of the problem which assumes a specific value while a particular pattern of disks is generated. When a growing disk overlaps for the first time with at least one other disk, its growth is stopped and is said to be frozen. In this paper we study the percolation properties of the set of frozen disks. Using numerical simulations we present evidence for the following: (i) The order parameter appears to jump discontinuously at a certain critical value of the area coverage; (ii) the width of the window of the area coverage needed to observe a macroscopic jump in the order parameter tends to vanish as ??0; and on the contrary (iii) the cluster size distribution has a power-law-decaying functional form. While the first two results are the signatures of a discontinuous transition, the third result is indicative of a continuous transition. Therefore we refer to this transition as a sharp but continuous transition similar to what has been observed in the recently introduced Achlioptas process of explosive percolation. It is also observed that in the limit of ??0, the critical area coverage at the transition point tends to unity, implying that the limiting pattern is space filling. In this limit, the fractal dimension of the pore space at the percolation point has been estimated to be 1.42(10) and the contact network of the disk assembly is found to be a scale-free network. PMID:24730786

Chakraborty, Abhijit; Manna, S S

2014-03-01

32

Space-filling percolation  

NASA Astrophysics Data System (ADS)

A region of two-dimensional space has been filled randomly with a large number of growing circular disks allowing only a "slight" overlapping among them just before their growth stops. More specifically, each disk grows from a nucleation center that is selected at a random location within the uncovered region. The growth rate ? is a continuously tunable parameter of the problem which assumes a specific value while a particular pattern of disks is generated. When a growing disk overlaps for the first time with at least one other disk, its growth is stopped and is said to be frozen. In this paper we study the percolation properties of the set of frozen disks. Using numerical simulations we present evidence for the following: (i) The order parameter appears to jump discontinuously at a certain critical value of the area coverage; (ii) the width of the window of the area coverage needed to observe a macroscopic jump in the order parameter tends to vanish as ? ?0; and on the contrary (iii) the cluster size distribution has a power-law-decaying functional form. While the first two results are the signatures of a discontinuous transition, the third result is indicative of a continuous transition. Therefore we refer to this transition as a sharp but continuous transition similar to what has been observed in the recently introduced Achlioptas process of explosive percolation. It is also observed that in the limit of ? ?0, the critical area coverage at the transition point tends to unity, implying that the limiting pattern is space filling. In this limit, the fractal dimension of the pore space at the percolation point has been estimated to be 1.42(10) and the contact network of the disk assembly is found to be a scale-free network.

Chakraborty, Abhijit; Manna, S. S.

2014-03-01

33

Percolation in magnetic composites  

Microsoft Academic Search

Electric and magnetic properties of composite materials consisting of low density polyethylene filled with powdered ferromagnetic\\u000a materials were investigated. The volume fractions of the fillers were varied from 10% up to the theoretical maximum packing\\u000a fractions, i.e. between 0.70 and 0.77, so that the percolation phenomenon could be investigated. The ferromagnetic fillers\\u000a used were HyMu 800 (a nickel-iron-molybdenum alloy), MnZn

T. J Fiske; H. S. GOKTURK; D. M Kalyon

1997-01-01

34

Gas percolation through sand  

NASA Astrophysics Data System (ADS)

Previous research has determined the shock properties of quartz sand. The effect of the physical processes occurring with varying moisture content and particle size were shock presented. In this study the same quartz sand, in a column is subjected to blast waves over a range of pressure. The diagnostics used are pressure sensors and high-speed photography. The effect of grain size on propagation time and the effect of moisture content are determined. Aspects of particle and liquid movement are also discussed. While the velocity of the percolation through the bed is primarily controlled by grain size the effect of moisture and liquids reveals a more complex dependence.

Proud, W. G.

2014-05-01

35

Ammonia (GCMP)  

NSDL National Science Digital Library

Ammonia fountain: this is a resource in the collection "General Chemistry Multimedia Problems". In an ammonia fountain, a flask is filled with ammonia gas. A tube from the flask extends into a pan of water that contains phenolphthalein. When a rubber bulb full of water is squeezed, the water squirts into the flask. Water from the pan then is pushed into the flask and the indicator changes color. General Chemistry Multimedia Problems ask students questions about experiments they see presented using videos and images. The questions asked apply concepts from different parts of an introductory course, encouraging students to decompartmentalize the material.

36

Crackling noise in fractional percolation.  

PubMed

Crackling noise is a common feature in many systems that are pushed slowly, the most familiar instance of which is the sound made by a sheet of paper when crumpled. In percolation and regular aggregation, clusters of any size merge until a giant component dominates the entire system. Here we establish 'fractional percolation', in which the coalescence of clusters that substantially differ in size is systematically suppressed. We identify and study percolation models that exhibit multiple jumps in the order parameter where the position and magnitude of the jumps are randomly distributed--characteristic of crackling noise. This enables us to express crackling noise as a result of the simple concept of fractional percolation. In particular, the framework allows us to link percolation with phenomena exhibiting non-self-averaging and power law fluctuations such as Barkhausen noise in ferromagnets. PMID:23887743

Schröder, Malte; Rahbari, S H Ebrahimnazhad; Nagler, Jan

2013-01-01

37

Percolation technique for galaxy clustering  

NASA Technical Reports Server (NTRS)

We study percolation in mass and galaxy distributions obtained in 3D simulations of the CDM, C + HDM, and the power law (n = -1) models in the Omega = 1 universe. Percolation statistics is used here as a quantitative measure of the degree to which a mass or galaxy distribution is of a filamentary or cellular type. The very fast code used calculates the statistics of clusters along with the direct detection of percolation. We found that the two parameters mu(infinity), characterizing the size of the largest cluster, and mu-squared, characterizing the weighted mean size of all clusters excluding the largest one, are extremely useful for evaluating the percolation threshold. An advantage of using these parameters is their low sensitivity to boundary effects. We show that both the CDM and the C + HDM models are extremely filamentary both in mass and galaxy distribution. The percolation thresholds for the mass distributions are determined.

Klypin, Anatoly; Shandarin, Sergei F.

1993-01-01

38

Recycling, Inc.  

ERIC Educational Resources Information Center

Suggestions for creating a successful office recycling system are enumerated from start up plans to waste reduction and paper recycling. Contact information for recycling equipment, potential buyers of recycled materials, recycled products for purchase, and ideas for promotion and education of staff are included. (MCO)

Martin, Amy

1992-01-01

39

Watersheds and Explosive percolation  

NASA Astrophysics Data System (ADS)

The recent work by Achlioptas, D'Souza, and Spencer opened up the possibility of obtaining a discontinuous (explosive) percolation transition by changing the stochastic rule of bond occupation. Despite the active research on this subject, several questions still remain open about the leading mechanism and the properties of the system. We review the largest cluster and the Gaussian models recently introduced. We show that, to obtain a discontinuous transition it is solely necessary to control the size of the largest cluster, suppressing the growth of a cluster di_ering significantly, in size, from the average one. As expected for a discontinuous transition, a Gaussian cluster-size distribution and compact clusters are obtained. The surface of the clusters is fractal, with the same fractal dimension of the watershed line.

Herrmann, Hans J.; Araujo, Nuno A. M.

40

Weak percolation on multiplex networks  

NASA Astrophysics Data System (ADS)

Bootstrap percolation is a simple but nontrivial model. It has applications in many areas of science and has been explored on random networks for several decades. In single-layer (simplex) networks, it has been recently observed that bootstrap percolation, which is defined as an incremental process, can be seen as the opposite of pruning percolation, where nodes are removed according to a connectivity rule. Here we propose models of both bootstrap and pruning percolation for multiplex networks. We collectively refer to these two models with the concept of "weak" percolation, to distinguish them from the somewhat classical concept of ordinary ("strong") percolation. While the two models coincide in simplex networks, we show that they decouple when considering multiplexes, giving rise to a wealth of critical phenomena. Our bootstrap model constitutes the simplest example of a contagion process on a multiplex network and has potential applications in critical infrastructure recovery and information security. Moreover, we show that our pruning percolation model may provide a way to diagnose missing layers in a multiplex network. Finally, our analytical approach allows us to calculate critical behavior and characterize critical clusters.

Baxter, Gareth J.; Dorogovtsev, Sergey N.; Mendes, José F. F.; Cellai, Davide

2014-04-01

41

Percolation of spatially constraint networks  

NASA Astrophysics Data System (ADS)

We study how spatial constraints are reflected in the percolation properties of networks embedded in one-dimensional chains and two-dimensional lattices. We assume long-range connections between sites on the lattice where two sites at distance r are chosen to be linked with probability p(r)~r-?. Similar distributions have been found in spatially embedded real networks such as social and airline networks. We find that for networks embedded in two dimensions, with 2percolation properties show new intermediate behavior different from mean field, with critical exponents that depend on ?. For ?<2, the percolation transition belongs to the universality class of percolation in Erdös-Rényi networks (mean field), while for ?>4 it belongs to the universality class of percolation in regular lattices. For networks embedded in one dimension, we find that, for ?<1, the percolation transition is mean field. For 12 there is no percolation transition as in regular linear chains.

Li, Daqing; Li, Guanliang; Kosmidis, Kosmas; Stanley, H. E.; Bunde, Armin; Havlin, Shlomo

2011-03-01

42

Development of Vapor-Phase Catalytic Ammonia Removal System  

NASA Technical Reports Server (NTRS)

A report describes recent accomplishments of a continuing effort to develop the vapor-phase catalytic ammonia removal (VPCAR) process for recycling wastewater for consumption by humans aboard a spacecraft in transit to Mars.

Flynn, Michael; Fisher, John; Kiss, Mark; Borchers, Bruce; Tleimat, Badawi; Tleimat, Maher; Quinn, Gregory; Fort, James; Nalette, Tim; Baker, Gale; Genovese, Joseph

2007-01-01

43

Stacked triangular lattice: Percolation properties  

NASA Astrophysics Data System (ADS)

The stacked triangular lattice has the shape of a triangular prism. In spite of being considered frequently in solid-state physics and materials science, its percolation properties have received little attention. We investigate several nonuniversal percolation properties on this lattice using Monte Carlo simulation. We show that the percolation threshold is pcbond=0.18602±0.00002 for bonds and pcsite=0.26240±0.00005 for sites. The number of clusters at the threshold per site is ncbond=0.28458±0.00005 and ncsite=0.03998±0.00005. The stacked triangular lattice is a convenient choice to study the RGB model [Schrenk , Sci. Rep.10.1038/srep00751 2, 751 (2012)]. We present results on this model and its scaling behavior at the percolation threshold.

Schrenk, K. J.; Araújo, N. A. M.; Herrmann, H. J.

2013-03-01

44

The Percolation Rate of a Soil  

NSDL National Science Digital Library

This activity demonstrates how particle size and soil texture control water flow, and therefore percolation rate, through a soil. Students will construct a percolation column from a plastic tube and use it to test the percolation rates of three separated soil fractions (sand, silt, and clay). They will add water to samples in the percolation column and record the time it takes to drain out. They then make duration, volume and percolation calculations and answer questions about the soil types.

45

Responsible recycling  

SciTech Connect

The issues that affect the recycling of lead-acid batteries and the challenges that this issue brings to both the lead industry and to the battery manufacturers are covered. Topics include the lead market (its size and structure), the economic constraints on the recycling system, recycling rates for batteries, the technology of recycling, and future considerations.

Pugh, A. (Britannia Refined Metals, Northfleet (United Kingdom))

1993-05-01

46

Preliminary analysis of the effects of sea water leakage on the performance of the ammonia cycle  

Microsoft Academic Search

The effects of water contamination on an OTEC power plant utilizing ammonia as the working fluid were investigated with reference to power cycles with and without recycle around the evaporator. The thermodynamic effects of increasing the water concentration in an optimized ammonia cycle plant were analyzed by means of the Han-Starling generalized correlation with appropriate parameters for ammonia-water mixtures. In

H. Hafezzadah; D. W. Johnson; K. E. Starling

1977-01-01

47

Jamming percolation in three dimensions  

NASA Astrophysics Data System (ADS)

We introduce a three-dimensional model for jamming and glasses, and prove that the fraction of frozen particles is discontinuous at the directed-percolation critical density. In agreement with the accepted scenario for jamming and glass transitions, this is a mixed-order transition; the discontinuity is accompanied by diverging length- and time-scales. Because one-dimensional directed-percolation paths comprise the backbone of frozen particles, the unfrozen rattlers may use the third dimension to travel between their cages. Thus the dynamics are diffusive on long times even above the critical density for jamming.

Ghosh, Antina; Teomy, Eial; Shokef, Yair

2014-04-01

48

Percolation disorder in chromatographic systems  

NASA Astrophysics Data System (ADS)

A pore space model is presented to describe the transport of mass within pore packings of chromatographic columns. The particle pore structure is conceptually represented by a network of capillaries subjected to bond percolation disorder. The efficiency of the system is assessed in terms of a mass dispersivity factor (h) which accounts for the band broadening of the peak response. The results show a large dispersivity at a percolation fraction near the threshold which reflects the critical properties of the structure with respect to connectivity and tortuosity.

Andrade, J. S.; Rajagopal, K.

1991-12-01

49

Recycle City  

NSDL National Science Digital Library

Recycle City contains an interactive city map that demonstrates how residents of every section of the city, formerly Dumptown, have recycled, reduced, and reused waste to turn their town around. There is a Dumptown Game with a Control Center to monitor displays while Dumptown changes as waste reduction programs are put in place. Students can create their own Recycle City scavenger hunt or go to the Activities area and see other ways to put Recycle City to use to help protect the environment.

1997-01-01

50

Hanford recycling.  

National Technical Information Service (NTIS)

This paper is a study of the past and present recycling efforts on the Hanford site and options for future improvements in the recycling program. Until 1996, recycling goals were voluntarily set by the waste generators: this year, DOE has imposed goals fo...

I. M. Leonard

1996-01-01

51

Percolation processes in monomer-polyatomic mixtures  

NASA Astrophysics Data System (ADS)

In this paper, the percolation of mixtures of monomers and polyatomic species ( k-mers) on a square lattice is studied. By means of a finite-size scaling analysis, the critical exponents and the scaling collapsing of the fraction of percolating lattices are found. A phase diagram separating a percolating from a non-percolating region is determined. The main features of the phase diagram are discussed in order to predict its evolution for larger k-mer sizes.

Dolz, M.; Nieto, F.; Ramirez-Pastor, A. J.

2007-01-01

52

RECYCLING TODAY  

NSDL National Science Digital Library

We have probably heard of recycling but what is it really and why is it so improtant to do? Please answer the questions below as well as visiting the different websites to explore what recycling really is. Form groups of 4 and explore the following websites as well as answer the questions which follow. The first website is of Recycle City where you will be exploring the City and how they recycle. Recyle City Why Recycling is Important Now please answer the following questions on paper. 1. What are the 3 R's? Explain in further ...

Smith, Miss

2010-12-03

53

Geometric structure of percolation clusters.  

PubMed

We investigate the geometric properties of percolation clusters by studying square-lattice bond percolation on the torus. We show that the density of bridges and nonbridges both tend to 1/4 for large system sizes. Using Monte Carlo simulations, we study the probability that a given edge is not a bridge but has both its loop arcs in the same loop and find that it is governed by the two-arm exponent. We then classify bridges into two types: branches and junctions. A bridge is a branch iff at least one of the two clusters produced by its deletion is a tree. Starting from a percolation configuration and deleting the branches results in a leaf-free configuration, whereas, deleting all bridges produces a bridge-free configuration. Although branches account for ?43% of all occupied bonds, we find that the fractal dimensions of the cluster size and hull length of leaf-free configurations are consistent with those for standard percolation configurations. By contrast, we find that the fractal dimensions of the cluster size and hull length of bridge-free configurations are given by the backbone and external perimeter dimensions, respectively. We estimate the backbone fractal dimension to be 1.643 36(10). PMID:24580185

Xu, Xiao; Wang, Junfeng; Zhou, Zongzheng; Garoni, Timothy M; Deng, Youjin

2014-01-01

54

Spin Dynamics on Percolating Networks.  

National Technical Information Service (NTIS)

We have used inelastic neutron scattering to measure the order parameter relaxation rate GAMMA in the dilute, two-dimensional Ising antiferromagnet Rb sub 2 CoMg/sub 1-c/F sub 4 with c very close to the magnetic percolation threshold. Where kappa is the i...

G. Aeppli H. Guggenheim Y. J. Uemura

1985-01-01

55

Percolation mechanism for colossal magnetoresistance  

Microsoft Academic Search

We propose a new mechanism to explain colossal magnetoresistance. The explanation assumes that the materials displaying colossal magnetoresistance are halfmetallic and proposes that the effect is a critical phenomenon, which is intimately connected with the ferromagnetic-to-paramagnetic phase transition present in these materials. The proposed mechanism is a percolation mechanism; the behavior of the resistance is described using a resistor network.

Paul J. M. Bastiaansen; Hubert J. F. Knops

1998-01-01

56

Background Information on Ammonia.  

National Technical Information Service (NTIS)

Information on the synthesis, production, and use of ammonia (7664417) is reviewed. The importance of a catalyst in the process of uniting hydrogen and nitrogen to form ammonia, producers of ammonia between 1961 and 1974, their annual production capacity,...

R. Hartle

1975-01-01

57

Contact propagation: Percolation and other scaling regimes  

NASA Astrophysics Data System (ADS)

We examine the scaling behavior of stirred percolation and first-passage percolation systems in which cluster contact is rate limiting with respect to propagation or transport. For the scaling regime near the static percolation threshold, we provide details of previously reported computational estimates of the ``propagation exponent,'' and we present results for several variants of the stirred percolation model and for a first-passage percolation model. Five additional scaling regimes are predicted, three of which are verified computationally. Applications to combustion, diffusion-limited aggregation, gasification of porous solids, and crack propagation in solids are discussed.

Kerstein, Alan R.

1985-01-01

58

Explosive Percolation Transition is Actually Continuous  

NASA Astrophysics Data System (ADS)

Recently a discontinuous percolation transition was reported in a new “explosive percolation” problem for irreversible systems [D. Achlioptas, R. M. D’Souza, and J. Spencer, Science 323, 1453 (2009)SCIEAS0036-807510.1126/science.1167782] in striking contrast to ordinary percolation. We consider a representative model which shows that the explosive percolation transition is actually a continuous, second order phase transition though with a uniquely small critical exponent of the percolation cluster size. We describe the unusual scaling properties of this transition and find its critical exponents and dimensions.

da Costa, R. A.; Dorogovtsev, S. N.; Goltsev, A. V.; Mendes, J. F. F.

2010-12-01

59

Percolation in models of thin film depositions.  

PubMed

We have studied the percolation behavior of deposits for different (2+1)-dimensional models of surface layer formation. The mixed model of deposition was used, where particles were deposited selectively according to the random (RD) and ballistic (BD) deposition rules. In the mixed one-component models with deposition of only conducting particles, the mean height of the percolation layer (measured in monolayers) grows continuously from 0.898 32 for the pure RD model to 2.605 for the pure BD model, but the percolation transition belongs to the same universality class, as in the two-dimensional (2D) random percolation problem. In two-component models with deposition of conducting and isolating particles, the percolation layer height approaches infinity as concentration of the isolating particles becomes higher than some critical value. The crossover transition from 2D to 3D percolation was observed with increase of the percolation layer height. PMID:12513374

Lebovka, N I; Manna, S S; Tarafdar, S; Teslenko, N

2002-12-01

60

Asymmetrically Coupled Directed Percolation Systems  

NASA Astrophysics Data System (ADS)

We introduce a dynamical model of coupled directed percolation systems with two particle species. The two species A and B are coupled asymmetrically in that A particles branch B particles, whereas B particles prey on A particles. This model may describe epidemic spreading controlled by reactive immunization agents. We study nonequilibrium phase transitions with attention focused on the multicritical point where both species undergo the absorbing phase transition simultaneously. In one dimension, we find that the inhibitory coupling from B to A is irrelevant and the model belongs to the unidirectionally coupled directed percolation class. On the contrary, a mean-field analysis predicts that the inhibitory coupling is relevant and a new universality appears with a variable dynamic exponent. Numerical simulations on small-world networks confirm our predictions.

Noh, Jae Dong; Park, Hyunggyu

2005-04-01

61

Percolative fragmentation and spontaneous agglomeration  

SciTech Connect

Captive particle imaging experiments were performed on over 200 coal and char particles in the pulverized size range from four coals of various rank at oxygen concentration from 3--19 mol% and at gas temperatures of about 1250 K. Despite wide variations in single-particle behavior, the data set reveals two clear trends that provide new information on the nature of char combustion. First, the low-rank coal chars are observed to maintain their high reactivity through the late stages of combustion, thus avoiding the near-extinction events and long burnout tails observed for bituminous coal chars. Secondly, percolative fragmentation in the late stages of combustion is a rare event under these conditions. Some particles reach a percolation threshold rate in combustion, but typically undergo spontaneous agglomeration rather than liberation of the incipient fragments. It is concluded that percolative fragmentation behavior in the pulverized size range is determined not only by solid-phase connectivity, but also by a real competition between disruptive and cohesive forces present at the time of formation of the colloidal-sized incipient fragments.

Hurt, R.; Davis, K. [Sandia National Labs., Livermore, CA (United States). Combustion Research Facility] [Sandia National Labs., Livermore, CA (United States). Combustion Research Facility

1999-03-01

62

Analysis of the percolation cluster structure  

NASA Astrophysics Data System (ADS)

An implementation of algorithms for constructing and analyzing the cluster structure for a square quadruply connected lattice in the uncorrelated percolation problem is considered. Subsets of the complete superior hull and the skeleton of a percolation cluster are singled out using a modification of the Hoshen—Kopelman relabeling algorithm and the Bellman principle of optimality. The critical nature of the percolation process is demonstrated using the method for statistical tests, and the behavior of mass dimension is analyzed for various subsets of a percolation cluster.

Moskalev, P. V.

2009-06-01

63

Dependent percolation in two dimensions  

Microsoft Academic Search

.   For a natural number k, define an oriented site percolation on ?2 as follows. Let x\\u000a \\u000a i\\u000a , y\\u000a \\u000a j\\u000a be independent random variables with values uniformly distributed in {1, …, k}. Declare a site (i, j) ??2\\u000a closed if x\\u000a \\u000a i\\u000a = y\\u000a \\u000a j\\u000a , and open otherwise. Peter Winkler conjectured some years ago that if k? 4

P. N. Balister; B. Bollobás; A. M. Stacey

2000-01-01

64

Recycled Towers  

NSDL National Science Digital Library

Students learn about material reuse by designing and building the strongest and tallest towers they can, using only recycled materials. They follow design constraints and build their towers to withstand earthquake and high wind simulations.

Integrated Teaching And Learning Program

65

Recycle City  

NSDL National Science Digital Library

Recycling made fun. The Environmental Protection Agency's Recycle City Web site offers students an interactive way to learn how recycling can affect their environment. Users can click any part of the cartoon drawing of the city to learn about that particular building or site and what can be done to decrease waste. The site also contains a more involved exercise called the Dumptown game, where visitors click on City Hall to view various recycling programs and choose the program(s) the city will implement. Once implemented, that activity can be seen taking place in Dumptown. Although the Dumptown exercise may require the help of a teacher to navigate for younger students, both exercises are excellent for K-12 teachers and students.

1997-01-01

66

Ideas: Recycling.  

ERIC Educational Resources Information Center

Presents classroom ideas focusing on connections among mathematics, concern for the environment, and conservation of natural resources, including decomposition, water conservation, packaging materials, use of manufactured cans, and recycling. Includes reproducible student worksheets. (MKR)

Chessin, Debby A.; And Others

1994-01-01

67

A CHEMICAL PERCOLATION MODEL FOR DEVOLATILIZATION: SUMMARY  

Microsoft Academic Search

The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated coal based on the chemical structure of the parent coal. This document provides complete details of the development of the CPD model. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the

Thomas H. Fletcher; Alan R. Kerstein; Ronald J. Pugmire; Mark Solum; David M. Grant

68

Process for treating gases in the ammonia synthesis. [separation and dehydration of gases leaving synthesis reactor  

Microsoft Academic Search

In the synthesis of ammonia, a process is disclosed for treating the gases flowing from the synthesis reactor wherein those gases flow through a film absorber countercurrent to a cooled aqueous film to extract ammonia which is withdrawn as a strong solution from the absorber and scrubbed gases are combined for recycle with a stream of fresh feed which is

Guadalupi

1977-01-01

69

Textile recycling  

SciTech Connect

The most common household textiles include clothing, linens, draperies, carpets, shoes, handbags, and rugs. Old clothing, of course, is the most readily reused and/or recycled residentially generated textile category. State and/or local mandates to recycle a percentage of the waste stream are providing the impetus to add new materials to existing collection programs. Concurrently, the textile industry is aggressively trying to increase its throughput by seeking new sources of material to meet increased world demand for product. As experienced with drop-off programs for traditional materials, a majority of residents will not recycle materials unless the collection programs are convenient, i.e., curbside collection. The tonnage of marketable textiles currently being landfilled provide evidence of this. It is the authors' contention that if textile recycling is made convenient and accessible to every household in a municipality or region, then the waste stream disposed may be reduced in a similar fashion as when traditional recyclables are included in curbside programs.

Jablonowski, E. (Killam Associates, Millburn, NJ (United States)); Carlton, J.

1995-01-01

70

Advective transport in percolation clusters.  

PubMed

We simulate advective transport in bond percolation clusters at the critical point. We compute the histogram of flow speeds in each bond of the backbone and find the multifractal spectrum for two-dimensional lattices with linear dimension L2000 and in three dimensions for L250 . We demonstrate that in the limit of large systems all the negative moments of the velocity distribution become ill-defined. However, to model transport, the velocity histogram should be weighted by the flux to obtain a well-defined mean travel time. Finally, we use continuous time random walk theory to demonstrate that anomalous transport is observed whose characteristics can be related to the multifractal properties of the system. PMID:17358127

Rhodes, Matthew E; Blunt, Martin J

2007-01-01

71

Culling avalanches in bootstrap percolation  

NASA Astrophysics Data System (ADS)

We study the culling avalanches which occur after the “death” of a single randomly chosen site in a network where sites are unstable, and are culled, if they have coordination less than an integer parameter m . Avalanche distributions are presented for triangular and cubic lattices for values of m where the associated bootstrap transitions are either first or second order. In second order cases, the culling avalanche distribution is found to be exponential, while in first order cases it follows a power law. We present an exact relation between culling avalanches and conventional bootstrap percolation and show that a relation proposed by Manna [Physica A 261, 351 (1998)] can be a good approximation for strongly first order bootstrap transitions but not for continuous bootstrap transitions.

Farrow, C.; Duxbury, P. M.; Moukarzel, Cristian F.

2005-12-01

72

Recycling polyurethanes  

SciTech Connect

This article reports on the PolyUrethane Recycle and Recovery Council`s continuing evaluation of the technical and commercial viability of polyurethane recovery and recycling technologies. In North America, 240,000 tonnes of post-industrial and 16,000 tonnes of post-consumer polyurethane foam was recycled into carpet rebound underlay and other applications in 1993. Demand was so great in North America that 60,000 t of primarily post-industrial scarp was imported from Europe and the Far East. Polyurethane from the seats of the 9 million vehicles scrapped each year could yield 82,000 t of flexible post-consumer foam scrap: instrument and door panels could yield another 10,000 t of semi-flexible scrap.

NONE

1995-08-01

73

Tire Recycling  

NASA Technical Reports Server (NTRS)

Cryopolymers, Inc. tapped NASA expertise to improve a process for recycling vehicle tires by converting shredded rubber into products that can be used in asphalt road beds, new tires, hoses, and other products. In conjunction with the Southern Technology Applications Center and Stennis Space Center, NASA expertise in cryogenic fuel-handling needed for launch vehicle and spacecraft operations was called upon to improve the recycling concept. Stennis advised Cryopolymers on the type of equipment required, as well as steps to reduce the amount of liquid nitrogen used in the process. They also guided the company to use more efficient ways to control system hardware. It is estimated that more than 300 million tires nationwide are produced per year. Cryopolymers expects to reach a production rate of 5,000 tires recycled per day.

1997-01-01

74

Connectivity percolation of polydisperse anisotropic nanofillers  

NASA Astrophysics Data System (ADS)

We present a generalized connectedness percolation theory reduced to a compact form for a large class of anisotropic particle mixtures with variable degrees of connectivity. Even though allowing for an infinite number of components, we derive a compact yet exact expression for the mean cluster size of connected particles. We apply our theory to rodlike particles taken as a model for carbon nanotubes and find that the percolation threshold is sensitive to polydispersity in length, diameter, and the level of connectivity, which may explain large variations in the experimental values for the electrical percolation threshold in carbon-nanotube composites. The calculated connectedness percolation threshold depends only on a few moments of the full distribution function. If the distribution function factorizes, then the percolation threshold is raised by the presence of thicker rods, whereas it is lowered by any length polydispersity relative to the one with the same average length and diameter. We show that for a given average length, a length distribution that is strongly skewed to shorter lengths produces the lowest threshold relative to the equivalent monodisperse one. However, if the lengths and diameters of the particles are linearly correlated, polydispersity raises the percolation threshold and more so for a more skewed distribution toward smaller lengths. The effect of connectivity polydispersity is studied by considering nonadditive mixtures of conductive and insulating particles, and we present tentative predictions for the percolation threshold of graphene sheets modeled as perfectly rigid, disklike particles.

Otten, Ronald H. J.; van der Schoot, Paul

2011-03-01

75

Energy requirements of ammonia–carbon dioxide forward osmosis desalination  

Microsoft Academic Search

The energy requirements of ammonia–carbon dioxide forward osmosis (FO) desalination are predicted by the use of chemical process modeling software (HYSYS). The FO process is modeled using single or multiple distillation columns to separate draw solution solutes from the product water for solute recycling within the FO system. Thermal and electrical energy requirements of the process are calculated, as well

Robert L. McGinnis; Menachem Elimelech

2007-01-01

76

Endocytic recycling  

Microsoft Academic Search

After endocytosis, most membrane proteins and lipids return to the cell surface, but some membrane components are delivered to late endosomes or the Golgi. We now understand that the pathways taken by internalized molecules that eventually recycle to the cell surface can be surprisingly complex and can involve a series of sorting events that occur in several organelles. The molecular

Frederick R. Maxfield; Timothy E. McGraw

2004-01-01

77

Recycled soundscapes  

Microsoft Academic Search

An interactive system collects noise from a public place and transforms it into content for a public orchestration: the noise is split in specific sounds which are recomposed through sonic interface in a new soundscape. The SoundCam is the most visible part of the Recycling Soundscapes system. It rotates scanning a public space and gives the possibility to spy and

Karmen Franinovic; Yon Visell

2004-01-01

78

Recycling Philology.  

ERIC Educational Resources Information Center

Proposes that English teachers recycle philology as a field of study. Redefines the shape of philology in view of postmodern theories of signification. Considers concepts of hermeneutics in retheorizing the aims of philology. Shows how such philological investigation might be used in the classroom to study literary texts. (HB)

Knapp, Peggy A.

1993-01-01

79

Inducing effect on the percolation transition in complex networks  

NASA Astrophysics Data System (ADS)

Percolation theory concerns the emergence of connected clusters that percolate through a networked system. Previous studies ignored the effect that a node outside the percolating cluster may actively induce its inside neighbours to exit the percolating cluster. Here we study this inducing effect on the classical site percolation and K-core percolation, showing that the inducing effect always causes a discontinuous percolation transition. We precisely predict the percolation threshold and core size for uncorrelated random networks with arbitrary degree distributions. For low-dimensional lattices the percolation threshold fluctuates considerably over realizations, yet we can still predict the core size once the percolation occurs. The core sizes of real-world networks can also be well predicted using degree distribution as the only input. Our work therefore provides a theoretical framework for quantitatively understanding discontinuous breakdown phenomena in various complex systems.

Zhao, Jin-Hua; Zhou, Hai-Jun; Liu, Yang-Yu

2013-09-01

80

Inducing effect on the percolation transition in complex networks.  

PubMed

Percolation theory concerns the emergence of connected clusters that percolate through a networked system. Previous studies ignored the effect that a node outside the percolating cluster may actively induce its inside neighbours to exit the percolating cluster. Here we study this inducing effect on the classical site percolation and K-core percolation, showing that the inducing effect always causes a discontinuous percolation transition. We precisely predict the percolation threshold and core size for uncorrelated random networks with arbitrary degree distributions. For low-dimensional lattices the percolation threshold fluctuates considerably over realizations, yet we can still predict the core size once the percolation occurs. The core sizes of real-world networks can also be well predicted using degree distribution as the only input. Our work therefore provides a theoretical framework for quantitatively understanding discontinuous breakdown phenomena in various complex systems. PMID:24013476

Zhao, Jin-Hua; Zhou, Hai-Jun; Liu, Yang-Yu

2013-01-01

81

Lateral diffusion and percolation in membranes.  

PubMed

An algorithm based on Voronoi tessellation and percolation theory is presented to study the diffusion of model membrane components (solutes) in the plasma membrane. The membrane is modeled as a two-dimensional space with integral membrane proteins as static obstacles. The Voronoi diagram consists of vertices, which are equidistant from three matrix obstacles, joined by edges. An edge between two vertices is said to be connected if solute particles can pass directly between the two regions. The percolation threshold, pc, determined using this passage criterion is pc approximately equal to 0.53. This is smaller than if the connectivity of edges were assigned randomly, in which case the percolation threshold pr=2/3, where p is the fraction of connected edges. Molecular dynamics simulations show that diffusion is determined by percolation of clusters of edges. PMID:16803348

Sung, Bong June; Yethiraj, Arun

2006-06-01

82

Electron diffusion in percolating gold clusters  

Microsoft Academic Search

Static and dynamical properties of percolating gold films are investigated by means of computer simulations on digitized pictures taken from original TEM-micrographs. From the digitized pictures we calculate the percolation correlation length xip and determine the rms distance r of a random walk as function of time. For r

A. Carl; G. Dumpich; S. Friedrichowski

1992-01-01

83

Directed Percolation and the Golden Ratio  

Microsoft Academic Search

Applying the theory of Yang-Lee zeros to nonequilibrium critical phenomena,\\u000awe investigate the properties of a directed bond percolation process for a\\u000acomplex percolation parameter p. It is shown that for the Golden Ratio\\u000ap=(1(+\\/-)sqrt(5))\\/2 and for p=2 the survival probability of a cluster can be\\u000acomputed exactly.

Stephan M Dammer; Silvio R Dahmen; Haye Hinrichsenk

2001-01-01

84

Critical exponents of the explosive percolation transition  

NASA Astrophysics Data System (ADS)

In a new type of percolation phase transition, which was observed in a set of nonequilibrium models, each new connection between vertices is chosen from a number of possibilities by an Achlioptas-like algorithm. This causes preferential merging of small components and delays the emergence of the percolation cluster. First simulations led to a conclusion that a percolation cluster in this irreversible process is born discontinuously, by a discontinuous phase transition, which results in the term "explosive percolation transition." We have shown that this transition is actually continuous (second order) though with an anomalously small critical exponent of the percolation cluster. Here we propose an efficient numerical method enabling us to find the critical exponents and other characteristics of this second-order transition for a representative set of explosive percolation models with different number of choices. The method is based on gluing together the numerical solutions of evolution equations for the cluster size distribution and power-law asymptotics. For each of the models, with high precision, we obtain critical exponents and the critical point.

da Costa, R. A.; Dorogovtsev, S. N.; Goltsev, A. V.; Mendes, J. F. F.

2014-04-01

85

Precipitation Recycling  

NASA Technical Reports Server (NTRS)

The water cycle regulates and reflects natural variability in climate at the regional and global scales. Large-scale human activities that involve changes in land cover, such as tropical deforestation, are likely to modify climate through changes in the water cycle. In order to understand, and hopefully be able to predict, the extent of these potential global and regional changes, we need first to understand how the water cycle works. In the past, most of the research in hydrology focused on the land branch of the water cycle, with little attention given to the atmospheric branch. The study of precipitation recycling which is defined as the contribution of local evaporation to local precipitation, aims at understanding hydrologic processes in the atmospheric branch of the water cycle. Simply stated, any study on precipitation recycling is about how the atmospheric branch of the water cycle works, namely, what happens to water vapor molecules after they evaporate from the surface, and where will they precipitate?

Eltahir, Elfatih A. B.; Bras, Rafael L.

1996-01-01

86

Computer Recycling  

NSDL National Science Digital Library

Given current rates of computer consumerism and technological advances, one might expect to find a lot of computers out there in the world. What happens to these old computers? This Topic in Depth explores this issue, reviews some options for recycling computers, and provides tips for anyone considering purchasing a refurbished computer. The first article from BBC News (1) reports on research which suggests that "the number of personal computers worldwide is expected to double by 2010 to 1.3 billion machines." The second article from Oasis, a project of the Irish eGovernment initiative, (2) reviews some of the issues surrounding waste from electrical and electronic equipment. This next article from PC World (3) gives some ideas for how to dispose of an old notebook computer. One option, of course, is to donate your notebook, which is discussed in this article from Tech Soup (4). Another resource for information on computer recycling and reuse is this website from CompuMentor (5). Given the current market for computers, many are considering refurbished computers. This article from Vnunet (6 ) explains what a refurbished computer is while the next website provides some tips for buying a refurbished computer (7 ). Finally, this article from About.com reports on the recently introduced National Computer Recycling Act (8).

87

Application of percolation theory to microtomography of structured media: Percolation threshold, critical exponents, and upscaling  

NASA Astrophysics Data System (ADS)

Percolation theory provides a tool for linking microstructure and macroscopic material properties. In this paper, percolation theory is applied to the analysis of microtomographic images for the purpose of deriving scaling laws for upscaling of properties. We have tested the acquisition of quantities such as percolation threshold, crossover length, fractal dimension, and critical exponent of correlation length from microtomography. By inflating or deflating the target phase and percolation analysis, we can get a critical model and an estimation of the percolation threshold. The crossover length is determined from the critical model by numerical simulation. The fractal dimension can be obtained either from the critical model or from the relative size distribution of clusters. Local probabilities of percolation are used to extract the critical exponent of the correlation length. For near-isotropic samples such as sandstone and bread, the approach works very well. For strongly anisotropic samples, such as highly deformed rock (mylonite) and a tree branch, the percolation threshold and fractal dimension can be assessed with accuracy. However, the uncertainty of the correlation length makes it difficult to accurately extract its critical exponents. Therefore, this aspect of percolation theory cannot be reliably used for upscaling properties of strongly anisotropic media. Other methods of upscaling have to be used for such media.

Liu, Jie; Regenauer-Lieb, Klaus

2011-01-01

88

Application of percolation theory to microtomography of structured media: percolation threshold, critical exponents, and upscaling.  

PubMed

Percolation theory provides a tool for linking microstructure and macroscopic material properties. In this paper, percolation theory is applied to the analysis of microtomographic images for the purpose of deriving scaling laws for upscaling of properties. We have tested the acquisition of quantities such as percolation threshold, crossover length, fractal dimension, and critical exponent of correlation length from microtomography. By inflating or deflating the target phase and percolation analysis, we can get a critical model and an estimation of the percolation threshold. The crossover length is determined from the critical model by numerical simulation. The fractal dimension can be obtained either from the critical model or from the relative size distribution of clusters. Local probabilities of percolation are used to extract the critical exponent of the correlation length. For near-isotropic samples such as sandstone and bread, the approach works very well. For strongly anisotropic samples, such as highly deformed rock (mylonite) and a tree branch, the percolation threshold and fractal dimension can be assessed with accuracy. However, the uncertainty of the correlation length makes it difficult to accurately extract its critical exponents. Therefore, this aspect of percolation theory cannot be reliably used for upscaling properties of strongly anisotropic media. Other methods of upscaling have to be used for such media. PMID:21405743

Liu, Jie; Regenauer-Lieb, Klaus

2011-01-01

89

Percolation Centrality: Quantifying Graph-Theoretic Impact of Nodes during Percolation in Networks  

PubMed Central

A number of centrality measures are available to determine the relative importance of a node in a complex network, and betweenness is prominent among them. However, the existing centrality measures are not adequate in network percolation scenarios (such as during infection transmission in a social network of individuals, spreading of computer viruses on computer networks, or transmission of disease over a network of towns) because they do not account for the changing percolation states of individual nodes. We propose a new measure, percolation centrality, that quantifies relative impact of nodes based on their topological connectivity, as well as their percolation states. The measure can be extended to include random walk based definitions, and its computational complexity is shown to be of the same order as that of betweenness centrality. We demonstrate the usage of percolation centrality by applying it to a canonical network as well as simulated and real world scale-free and random networks.

Piraveenan, Mahendra; Prokopenko, Mikhail; Hossain, Liaquat

2013-01-01

90

Assessing Ammonia Treatment Options  

EPA Science Inventory

This is the second of three articles to help water system operators understand ammonia and how to monitor and control its effects at the plant and in the distribution system. The first article (Opflow, April 2012) provided an overview of ammonia's chemistry, origins, and water sy...

91

Method for forming ammonia  

DOEpatents

A method for forming ammonia is disclosed and which includes the steps of forming a plasma; providing a source of metal particles, and supplying the metal particles to the plasma to form metal nitride particles; and providing a substance, and reacting the metal nitride particles with the substance to produce ammonia, and an oxide byproduct.

Kong; Peter C. (Idaho Falls, ID) [Idaho Falls, ID; Pink, Robert J. (Pocatello, ID) [Pocatello, ID; Zuck, Larry D. (Idaho Falls, ID) [Idaho Falls, ID

2008-08-19

92

Transport and percolation in complex networks  

NASA Astrophysics Data System (ADS)

To design complex networks with optimal transport properties such as flow efficiency, we consider three approaches to understanding transport and percolation in complex networks. We analyze the effects of randomizing the strengths of connections, randomly adding long-range connections to regular lattices, and percolation of spatially constrained networks. Various real-world networks often have links that are differentiated in terms of their strength, intensity, or capacity. We study the distribution P(?) of the equivalent conductance for Erdo?s-Rényi (ER) and scale-free (SF) weighted resistor networks with N nodes, for which links are assigned with conductance ? i ? e-axi, where xi is a random variable with 0 < xi < 1. We find, both analytically and numerically, that P(?) for ER networks exhibits two regimes: (i) For ? < e-apc, P(?) is independent of N and scales as a power law P(?) ˜ sk/a-1 . Here pc = 1/ is the critical percolation threshold of the network and is the average degree of the network. (ii) For ? > e -apc, P(?) has strong N dependence and scales as P(?) ˜ f(?, apc/N1/3). Transport properties are greatly affected by the topology of networks. We investigate the transport problem in lattices with long-range connections and subject to a cost constraint, seeking design principles for optimal transport networks. Our network is built from a regular d-dimensional lattice to be improved by adding long-range connections with probability Pij ˜ r-aij , where rij is the lattice distance between site i and j. We introduce a cost constraint on the total length of the additional links and find optimal transport in the system for ? = d + 1, established here for d = 1, 2 and 3 for regular lattices and df for fractals. Remarkably, this cost constraint approach remains optimal, regardless of the strategy used for transport, whether based on local or global knowledge of the network structure. To further understand the role that long-range connections play in optimizing the transport of complex systems, we study the percolation of spatially constrained networks. We now consider originally empty lattices embedded in d dimensions by adding long-range connections with the same power law probability p(r) ˜ r -?. We find that, for ? ? d, the percolation transition belongs to the universality class of percolation in ER networks, while for ? > 2d it belongs to the universality class of percolation in regular lattices (for one-dimensional linear chain, there is no percolation transition). However for d < ? < 2d, the percolation properties show new intermediate behavior different from ER networks, with critical exponents that depend on ?.

Li, Guanliang

93

Green Science: Revisiting Recycling  

ERIC Educational Resources Information Center

Recycling has been around for a long time--people have reused materials and refashioned them into needed items for thousands of years. More recently, war efforts encouraged conservation and reuse of materials, and in the 1970s recycling got its official start when recycling centers were created. Now, curbside recycling programs and recycling

Palliser, Janna

2011-01-01

94

Weakly explosive percolation in directed networks  

NASA Astrophysics Data System (ADS)

Percolation, the formation of a macroscopic connected component, is a key feature in the description of complex networks. The dynamical properties of a variety of systems can be understood in terms of percolation, including the robustness of power grids and information networks, the spreading of epidemics and forest fires, and the stability of gene regulatory networks. Recent studies have shown that if network edges are added “competitively” in undirected networks, the onset of percolation is abrupt or “explosive.” The unusual qualitative features of this phase transition have been the subject of much recent attention. Here we generalize this previously studied network growth process from undirected networks to directed networks and use finite-size scaling theory to find several scaling exponents. We find that this process is also characterized by a very rapid growth in the giant component, but that this growth is not as sudden as in undirected networks.

Squires, Shane; Sytwu, Katherine; Alcala, Diego; Antonsen, Thomas M.; Ott, Edward; Girvan, Michelle

2013-05-01

95

Weakly explosive percolation in directed networks.  

PubMed

Percolation, the formation of a macroscopic connected component, is a key feature in the description of complex networks. The dynamical properties of a variety of systems can be understood in terms of percolation, including the robustness of power grids and information networks, the spreading of epidemics and forest fires, and the stability of gene regulatory networks. Recent studies have shown that if network edges are added "competitively" in undirected networks, the onset of percolation is abrupt or "explosive." The unusual qualitative features of this phase transition have been the subject of much recent attention. Here we generalize this previously studied network growth process from undirected networks to directed networks and use finite-size scaling theory to find several scaling exponents. We find that this process is also characterized by a very rapid growth in the giant component, but that this growth is not as sudden as in undirected networks. PMID:23767507

Squires, Shane; Sytwu, Katherine; Alcala, Diego; Antonsen, Thomas M; Ott, Edward; Girvan, Michelle

2013-05-01

96

Discrete time quantum walks on percolation graphs  

NASA Astrophysics Data System (ADS)

Randomly breaking connections in a graph alters its transport properties, a model used to describe percolation. In the case of quantum walks, dynamic percolation graphs represent a special type of imperfections, where the connections appear and disappear randomly in each step during the time evolution. The resulting open system dynamics is hard to treat numerically in general. We shortly review the literature on this problem. We then present our method to solve the evolution on finite percolation graphs in the long time limit, applying the asymptotic methods concerning random unitary maps. We work out the case of one-dimensional chains in detail and provide a concrete, step-by-step numerical example in order to give more insight into the possible asymptotic behavior. The results about the case of the two-dimensional integer lattice are summarized, focusing on the Grover-type coin operator.

Kollár, Bálint; Novotný, Jaroslav; Kiss, Tamás; Jex, Igor

2014-05-01

97

Percolation effects on the decay of admolecules  

NASA Astrophysics Data System (ADS)

The effects of percolation on the energy transfer from an admolecule to a two-component granular composite substrate are investigated. The substrate material is a random mixture of a metal and an insulator nonabsorptive to the light. The luminescence decay rate of the admolecule near the composite surface is calculated by means of the effective-medium theory as a function of the volume fraction of the metallic granules. It is found that the decay rate is greatly enhanced around the dc conduction percolation threshold at low transition frequencies. For high frequencies, the decay rate peaks at a higher volume fraction of the metallic particles, indicating the existence of a ``surface-percolation'' threshold.

Lin, D. L.; Li, Xiao-Shen; Li, Zhen-Ya; George, Thomas F.

1992-02-01

98

Molecular Structure of Ammonia  

NSDL National Science Digital Library

Ammonia is a non-ionic colorless gas at ambient temperatures and a hydrogen bonding liquid at 240 Kelvin that has the remarkable ability to dissolve alkali metals. Ammonia is a Lewis base and is readily absorbed by water to form small amounts of ammonium hydroxide (pKb = 4.74). Naturally, ammonia has its sources in the biosphere (the nitrogen cycle) and is a trace gas in air and a source of ammonium ions in rain and atmospheric aerosols. Ammonia is prepared industrially by the Haber-Bosch process in quantities exceeding 120 million metric tons per year. In this process, ammonia gas is formed when hydrogen and nitrogen (3:1) are compressed to pressures of 200 atm and passed over an iron catalyst at 380-450 degrees C. Much of the ammonia produced this way (85%) is used as fertilizers on crops, a significant portion of which leaches from croplands into streams causing nitrate pollution and eutrophication of waterways (e.g., dead-zone in the Gulf of Mexico). Other sources of ammonia include combustion (coal and biomass burning) and from bacterial decomposition of animal excreta.

2006-05-02

99

Interval percolation and ceramic-metal composite  

NASA Astrophysics Data System (ADS)

The mixture of the BaTiO3 ceramic powder and silver ink was baked, and the bulk property of positive temperature coefficient (PTC) of BaTiO3 was recovered in the composite. An interval percolation model was put forward to describe this composite. Monte-Carlo simulation confirmed that the bulk property can be surely recovered in a cubic network if the fraction of conductive sites is in the range of 0.101-0.311. Moreover, experimental works indicated that the percolation threshold decreased with the increase of the size of ceramic particles, and the PTC bulk property appeared more obviously at higher electrical field.

Cheng, Yonghong; Wu, Kai; Chen, Xiaolin; Chen, Yu; Meng, Yongpeng

2007-12-01

100

Ammonia Leak Locator Study  

NASA Technical Reports Server (NTRS)

The thermal control system of International Space Station Alpha will use liquid ammonia as the heat exchange fluid. It is expected that small leaks (of the order perhaps of one pound of ammonia per day) may develop in the lines transporting the ammonia to the various facilities as well as in the heat exchange equipment. Such leaks must be detected and located before the supply of ammonia becomes critically low. For that reason, NASA-JSC has a program underway to evaluate instruments that can detect and locate ultra-small concentrations of ammonia in a high vacuum environment. To be useful, the instrument must be portable and small enough that an astronaut can easily handle it during extravehicular activity. An additional complication in the design of the instrument is that the environment immediately surrounding ISSA will contain small concentrations of many other gases from venting of onboard experiments as well as from other kinds of leaks. These other vapors include water, cabin air, CO2, CO, argon, N2, and ethylene glycol. Altogether, this local environment might have a pressure of the order of 10(exp -7) to 10(exp -6) torr. Southwest Research Institute (SwRI) was contracted by NASA-JSC to provide support to NASA-JSC and its prime contractors in evaluating ammonia-location instruments and to make a preliminary trade study of the advantages and limitations of potential instruments. The present effort builds upon an earlier SwRI study to evaluate ammonia leak detection instruments [Jolly and Deffenbaugh]. The objectives of the present effort include: (1) Estimate the characteristics of representative ammonia leaks; (2) Evaluate the baseline instrument in the light of the estimated ammonia leak characteristics; (3) Propose alternative instrument concepts; and (4) Conduct a trade study of the proposed alternative concepts and recommend promising instruments. The baseline leak-location instrument selected by NASA-JSC was an ion gauge.

Dodge, Franklin T.; Wuest, Martin P.; Deffenbaugh, Danny M.

1995-01-01

101

Percolation model for selective dissolution of multi-component glasses.  

National Technical Information Service (NTIS)

A percolation model is developed which accounts for most known features of the process of porous glass membrane preparation by selective dissolution of multi-component glasses. The model is founded within tile framework of the classical percolation theory...

R. P. Kale C. J. Brinker

1995-01-01

102

Recycling: Additional Efforts Could Increase Municipal Recycling.  

National Technical Information Service (NTIS)

Although recycling can generate environmental and economic benefits, the national recycling rate has increased only slightly since 2000, according to the Environmental Protection Agency (EPA). While local governments have the primary role in operating rec...

2006-01-01

103

Reactor for removing ammonia  

DOEpatents

Disclosed is a device for removing trace amounts of ammonia from a stream of gas, particularly hydrogen gas, prepared by a reformation apparatus. The apparatus is used to prevent PEM "poisoning" in a fuel cell receiving the incoming hydrogen stream.

Luo, Weifang (Livermore, CA); Stewart, Kenneth D. (Valley Springs, CA)

2009-11-17

104

Ammonia Release on ISS  

NASA Technical Reports Server (NTRS)

Crew: Approximately 53% metabolic load Product of protein metabolism Limit production of ammonia by external regulation NOT possbile Payloads Potential source Scientific experiments Thorough safety review ensures sufficient levels of containment

Macatangay, Ariel

2009-01-01

105

Monte Carlo renormalization-group analysis of percolation.  

PubMed

We describe a Monte Carlo renormalization group approach to the calculation of critical behavior for percolation models. This approach can be utilized to determine the renormalized bond probabilities and the values of the critical exponents. We illustrate the method for two-dimensional bond percolation, but the method is also applicable to other percolation models and other dimensions. PMID:24229304

Brown, Albert; Edelman, Alexander; Rocks, Jason; Coniglio, Antonio; Swendsen, Robert H

2013-10-01

106

Percolation theory and its application to groundwater hydrology  

Microsoft Academic Search

The theory of percolation, originally proposed over 30 years ago to describe flow phenomena in porous media, has undergone enormous development in recent years, primarily in the field of physics. The principal advantage of percolation theory is that it provides universal laws which determine the geometrical and physical properties of the system. This survey discusses developments and results in percolation

Brian Berkowitz; Isaac Balberg

1993-01-01

107

A Percolation Model of Thermal Conductivity for Filled Polymer Composites  

Microsoft Academic Search

In view of the shape and distribution of fillers, a model predicting the effective thermal conductivity of filled polymer composites is proposed on the basis of the percolation theory. Compared to other models proposed in the literatures, theoretical results obtained with the percolation model agree better with the experimental data. Methods of determining the percolation threshold Vc and the exponent

Guoqing Zhang; Yanping Xia; Hui Wang; Yu Tao; Guoliang Tao; Shantung Tu; Haiping Wu

2010-01-01

108

Site-percolation threshold of carbon nanotube fibers-Fast inspection of percolation with Markov stochastic theory  

NASA Astrophysics Data System (ADS)

We present a site-percolation model based on a modified FCC lattice, as well as an efficient algorithm of inspecting percolation which takes advantage of the Markov stochastic theory, in order to study the percolation threshold of carbon nanotube (CNT) fibers. Our Markov-chain based algorithm carries out the inspection of percolation by performing repeated sparse matrix-vector multiplications, which allows parallelized computation to accelerate the inspection for a given configuration. With this approach, we determine that the site-percolation transition of CNT fibers occurs at pc=0.1533±0.0013, and analyze the dependence of the effective percolation threshold (corresponding to 0.5 percolation probability) on the length and the aspect ratio of a CNT fiber on a finite-size-scaling basis. We also discuss the aspect ratio dependence of percolation probability with various values of p (not restricted to pc).

Xu, Fangbo; Xu, Zhiping; Yakobson, Boris I.

2014-08-01

109

Approximate symmetry laws for percolation in complex systems: Percolation in polydisperse composites  

NASA Astrophysics Data System (ADS)

The concept of so-called global symmetry of percolation models is discussed and extended to multicolored models. An integral equation is obtained, which determines the partial percolation probabilities Pa for sites of color a. This equation is applied to a polydisperse particulate composite: a mixture of conducting (of relative fraction xm) and nonconducting spheres with distributions of sizes nm(R) and ni(R), respectively. We find the probability PR for a conducting particle of radius R to belong to the percolation cluster as a function of xm and a functional of nm(R') and ni(R'). The percolation threshold x is shown to decrease with increasing dispersion ? of particle sizes. A simple law x=1/(3[1+(?/4)]) is obtained in the range of moderate dispersions. The theory is applicable also to a mixture of electronic and ionic conductors.

Ioselevich, Alexei S.; Kornyshev, Alexei A.

2002-02-01

110

Bootstrap Percolation: A Renormalisation Group Approach.  

National Technical Information Service (NTIS)

In bootstrap percolation, sites are occupied at random with probability p, but each site is considered active only if at least m of its neighbors are also active. Within an approximate position-space renormalisation group framework on a square lattice, we...

N. S. Branco R. R. dos Santos S. L. A. de Queiroz

1983-01-01

111

Temporal percolation in activity-driven networks  

NASA Astrophysics Data System (ADS)

We study the temporal percolation properties of temporal networks by taking as a representative example the recently proposed activity-driven-network model [N. Perra et al., Sci. Rep. 2, 469 (2012), 10.1038/srep00469]. Building upon an analytical framework based on a mapping to hidden variables networks, we provide expressions for the percolation time Tp marking the onset of a giant connected component in the integrated network. In particular, we consider both the generating function formalism, valid for degree-uncorrelated networks, and the general case of networks with degree correlations. We discuss the different limits of the two approaches, indicating the parameter regions where the correlated threshold collapses onto the uncorrelated case. Our analytical predictions are confirmed by numerical simulations of the model. The temporal percolation concept can be fruitfully applied to study epidemic spreading on temporal networks. We show in particular how the susceptible-infected-removed model on an activity-driven network can be mapped to the percolation problem up to a time given by the spreading rate of the epidemic process. This mapping allows us to obtain additional information on this process, not available for previous approaches.

Starnini, Michele; Pastor-Satorras, Romualdo

2014-03-01

112

Temporal percolation in activity-driven networks.  

PubMed

We study the temporal percolation properties of temporal networks by taking as a representative example the recently proposed activity-driven-network model [N. Perra et al., Sci. Rep. 2, 469 (2012)]. Building upon an analytical framework based on a mapping to hidden variables networks, we provide expressions for the percolation time Tp marking the onset of a giant connected component in the integrated network. In particular, we consider both the generating function formalism, valid for degree-uncorrelated networks, and the general case of networks with degree correlations. We discuss the different limits of the two approaches, indicating the parameter regions where the correlated threshold collapses onto the uncorrelated case. Our analytical predictions are confirmed by numerical simulations of the model. The temporal percolation concept can be fruitfully applied to study epidemic spreading on temporal networks. We show in particular how the susceptible-infected-removed model on an activity-driven network can be mapped to the percolation problem up to a time given by the spreading rate of the epidemic process. This mapping allows us to obtain additional information on this process, not available for previous approaches. PMID:24730899

Starnini, Michele; Pastor-Satorras, Romualdo

2014-03-01

113

Movement of Trace Metals with Percolating Water.  

National Technical Information Service (NTIS)

The major objective was to study the mechanism of movement of trace metals in soils with percolating water. The parameters that were considered to affect the metal ion movement in soil included: Soil texture, type and content of clay mineral, metal ion, h...

M. C. Wang V. A. Nacci

1975-01-01

114

Percolating Conduction in Finite Nanotube Networks  

Microsoft Academic Search

The percolating conductance of a new class of nanocomposite thin-film transistors, with channels composed of isotropic ensembles of nanotubes or nanowires, is analyzed as a function of wire\\/tube density and channel length. The conductance exponents are validated against analytical results for short channel transistors, and against available experimental data for longer channel devices. Our plots of conductance exponents as a

S. Kumar; J. Y. Murthy; M. A. Alam

2005-01-01

115

Dispersed ionic conductors and percolation theory  

Microsoft Academic Search

We suggest that ionic conductors containing a dispersed insulating phase are suitable materials for investigating static and kinetic aspects of percolation. We develop a lattice model for the two-phase mixture with special emphasis on the role of an enhanced interface conductivity. By using two-dimensional Monte Carlo simulations we show that our model correctly describes the distinct conduction properties of those

A. Bunde; W. Dieterich; E. Roman

1985-01-01

116

Social Percolation on Inhomogeneous Spanning Network  

NASA Astrophysics Data System (ADS)

The Social Percolation model recently proposed by Solomon et al. is studied on the Ising correlated inhomogeneous network. The dynamics in this is studied so as to understand the role of correlations in the social structure. Thus, the possible role of the structural social connectivity is examined.

Gupta, Abhijit Kar; Stauffer, Dietrich

117

Percolation on general trees and HIV modeling  

NASA Astrophysics Data System (ADS)

Percolation on a general tree is studied. A general tree is used to model the transition from HIV infection into AIDS and to explain the large differences of the transition time from one patient to another. HIV has some autoimmune effects due to its low antigenic mutants. Fuzzy mathematics is used to explain these effects.

Ahmed, E.; Agiza, H. N.

1996-12-01

118

Percolation in directed scale-free networks  

Microsoft Academic Search

Many complex networks in nature have directed links, a property that affects the network's navigability and large-scale topology. Here we study the percolation properties of such directed scale-free networks with correlated in and out degree distributions. We derive a phase diagram that indicates the existence of three regimes, determined by the values of the degree exponents. In the first regime

N. Schwartz; R. Cohen; D. Ben-Avraham; A.-L. Barabási; S. Havlin

2002-01-01

119

PREDICTING ATTENUATION OF VIRUSES IN PERCOLATING WATER  

EPA Science Inventory

A new screening model developed by EPA can be used to predict the fate of viruses in percolating water. The model can be used even when limited information is available, provided the user is willing to accept the quality and quantity of the data at hand. We present a simple GIS...

120

Connected Components in Supercritical Mandelbrot Percolation.  

National Technical Information Service (NTIS)

The limiting set of the supercritical Mandelbrot percolation process is investigated. It is shown that the number of components which intersect the left and the right side of the unit square is finite a.s. Other components in the limiting set are studied....

R. W. J. Meester

1990-01-01

121

Connected Components in Supercritical Mandelbrot Percolation.  

National Technical Information Service (NTIS)

The paper investigates the limiting set of the supercritical Mandelbrot percolation process. In particular, it shows that the number of components which intersect the left and right side of the unit square is finite. It also studies other components in th...

R. W. J. Meester

1990-01-01

122

Superdiffusivity in first-passage percolation  

Microsoft Academic Search

Summary.  In standard first-passage percolation on (with ), the time-minimizing paths from a point to a plane at distance are expected to have transverse fluctuations of order . It has been conjectured that with the inequality strict (superdiffusivity) at least for low and with . We prove (versions of) for all and .

C. Licea; C. M. Newman; M. S. T. Piza

1996-01-01

123

Crossover from isotropic to directed percolation  

NASA Astrophysics Data System (ADS)

We generalize the directed percolation (DP) model by relaxing the strict directionality of DP such that propagation can occur in either direction but with anisotropic probabilities. We denote the probabilities as p?=ppd and p?=p(1-pd), with p representing the average occupation probability and pd controlling the anisotropy. The Leath-Alexandrowicz method is used to grow a cluster from an active seed site. We call this model with two main growth directions biased directed percolation (BDP). Standard isotropic percolation (IP) and DP are the two limiting cases of the BDP model, corresponding to pd=1/2 and pd=0,1 respectively. In this work, besides IP and DP, we also consider the 1/2percolation thresholds of the BDP model for pd=0.6 and 0.8, and determine various critical exponents. These exponents are found to be consistent with those for standard DP. We also determine the renormalization exponent associated with the asymmetric perturbation due to pd-1/2?0 near IP, and confirm that such an asymmetric scaling field is relevant at IP.

Zhou, Zongzheng; Yang, Ji; Ziff, Robert M.; Deng, Youjin

2012-08-01

124

Simple percolation experiment in two dimensions  

NSDL National Science Digital Library

A simple experiment for the demonstration of percolation problems is reported. Measurements were performed on a sheet of conducting paper after randomly cutting out small square âsitesâ at a concentration 1?p. The conductance and the area fraction covered by the infinite cluster were evaluated as a function of p. This experiment is appropriate as an introduction to the teaching of phase transitions.

Mehr, Ramit; Grossman, Tal; Kristianpoller, N.; Gefen, Yuval

2011-08-30

125

Ammonia Clouds on Jupiter  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Click on the image for movie of Ammonia Ice Clouds on Jupiter

In this movie, put together from false-color images taken by the New Horizons Ralph instrument as the spacecraft flew past Jupiter in early 2007, show ammonia clouds (appearing as bright blue areas) as they form and disperse over five successive Jupiter 'days.' Scientists noted how the larger cloud travels along with a small, local deep hole.

2007-01-01

126

Disinfection of secondary effluents by infiltration percolation.  

PubMed

Among the most attractive applications of reclaimed wastewater are: irrigation of public parks, sports fields, golf courses and market gardening. These uses require advanced wastewater treatment including disinfection. According to WHO guidelines (1989) and current rules and regulations in Tunisia, faecal coliform levels have to be reduced to < 10(3) or 10(2) CFU/100 mL. In Tunisia, most wastewater plants are only secondary treatment and, in order to meet health related regulations, the effluents need to be disinfected. However, it is usual for secondary effluents to need filtration prior to disinfection. Effectiveness of conventional disinfection processes, such as chlorination and UV radiation, are dependent upon the oxidation level and the levels of suspended solids of the treated water. Ozonation is relatively expensive and energy consuming. The consideration of the advantages and disadvantages of conventional techniques, their reliability, investment needs and operational costs will lead to the use of less sophisticated alternative techniques for certain facilities. Among alternative techniques, soil aquifer treatment and infiltration percolation through sand beds have been studied in Arizona, Israel, France, Spain and Morocco. Infiltration percolation plants have been intermittently fed with secondary or high quality primary effluents which percolated through 1.5-2 m unsaturated coarse sand and were recovered by under-drains. In such infiltration percolation facilities, microorganisms were eliminated through numerous physical, physicochemical and biological inter-related processes (mechanical filtration, adsorption and microbial degradation respectively). Efficiency of faecal coliform removal was dependent upon the water detention times in the filtering medium and on the oxidation of the filtered water. Effluents of Sfax town aerated ponds were infiltrated through 1.5 m deep sand columns in order to determine the performance of infiltration percolation in the polishing of secondary effluents. Elimination of bacteria (total and coliforms, faecal streptococci) and their relationship with the hydraulic load and the temperature were investigated. PMID:11464749

Makni, H

2001-01-01

127

Recycling Improves USA  

Microsoft Academic Search

Changes are occurring in recycling that will improve the United States. There are significant improvements in the economy, environment and the health of Americans due to recycling efforts. Recycling will be shown as a superior option compared to landfill, incineration and virgin material processing. Many Case studies will be discussed that show how communities are making long-term decisions for recycling.

Luke Monroe

128

Percolation of a general network of networks  

NASA Astrophysics Data System (ADS)

Percolation theory is an approach to study the vulnerability of a system. We develop an analytical framework and analyze the percolation properties of a network composed of interdependent networks (NetONet). Typically, percolation of a single network shows that the damage in the network due to a failure is a continuous function of the size of the failure, i.e., the fraction of failed nodes. In sharp contrast, in NetONet, due to the cascading failures, the percolation transition may be discontinuous and even a single node failure may lead to an abrupt collapse of the system. We demonstrate our general framework for a NetONet composed of n classic Erd?s-Rényi (ER) networks, where each network depends on the same number m of other networks, i.e., for a random regular network (RR) formed of interdependent ER networks. The dependency between nodes of different networks is taken as one-to-one correspondence, i.e., a node in one network can depend only on one node in the other network (no-feedback condition). In contrast to a treelike NetONet in which the size of the largest connected cluster (mutual component) depends on n, the loops in the RR NetONet cause the largest connected cluster to depend only on m and the topology of each network but not on n. We also analyzed the extremely vulnerable feedback condition of coupling, where the coupling between nodes of different networks is not one-to-one correspondence. In the case of NetONet formed of ER networks, percolation only exhibits two phases, a second order phase transition and collapse, and no first order percolation transition regime is found in the case of the no-feedback condition. In the case of NetONet composed of RR networks, there exists a first order phase transition when the coupling strength q (fraction of interdependency links) is large and a second order phase transition when q is small. Our insight on the resilience of coupled networks might help in designing robust interdependent systems.

Gao, Jianxi; Buldyrev, Sergey V.; Stanley, H. Eugene; Xu, Xiaoming; Havlin, Shlomo

2013-12-01

129

Percolation of a general network of networks.  

PubMed

Percolation theory is an approach to study the vulnerability of a system. We develop an analytical framework and analyze the percolation properties of a network composed of interdependent networks (NetONet). Typically, percolation of a single network shows that the damage in the network due to a failure is a continuous function of the size of the failure, i.e., the fraction of failed nodes. In sharp contrast, in NetONet, due to the cascading failures, the percolation transition may be discontinuous and even a single node failure may lead to an abrupt collapse of the system. We demonstrate our general framework for a NetONet composed of n classic Erd?s-Rényi (ER) networks, where each network depends on the same number m of other networks, i.e., for a random regular network (RR) formed of interdependent ER networks. The dependency between nodes of different networks is taken as one-to-one correspondence, i.e., a node in one network can depend only on one node in the other network (no-feedback condition). In contrast to a treelike NetONet in which the size of the largest connected cluster (mutual component) depends on n, the loops in the RR NetONet cause the largest connected cluster to depend only on m and the topology of each network but not on n. We also analyzed the extremely vulnerable feedback condition of coupling, where the coupling between nodes of different networks is not one-to-one correspondence. In the case of NetONet formed of ER networks, percolation only exhibits two phases, a second order phase transition and collapse, and no first order percolation transition regime is found in the case of the no-feedback condition. In the case of NetONet composed of RR networks, there exists a first order phase transition when the coupling strength q (fraction of interdependency links) is large and a second order phase transition when q is small. Our insight on the resilience of coupled networks might help in designing robust interdependent systems. PMID:24483520

Gao, Jianxi; Buldyrev, Sergey V; Stanley, H Eugene; Xu, Xiaoming; Havlin, Shlomo

2013-12-01

130

Restoring site percolation on damaged square lattices.  

PubMed

Restoring site percolation on a damaged square lattice with the nearest neighbor (N2) is investigated using two different strategies. In the first one, a density y of new sites are created on the empty sites with longer range links, either next-nearest neighbor (N3) or next-next-nearest neighbor (N4), but without N2. In the second one, new longer range links N3 or N4 are added to N2 but only for a fraction v of the remaining non-destroyed sites. Starting at p(c)(N2), with a density x of randomly destroyed sites, the values of y(c) and v(c), which restore site percolation, are calculated for both strategies with, respectively, N3 and N4 using Monte Carlo simulations. Results are obtained for the whole range 0 < or = x < or = p(c)(N2). PMID:16196753

Galam, Serge; Malarz, Krzysztof

2005-08-01

131

Discontinuous percolation transitions in real physical systems  

NASA Astrophysics Data System (ADS)

We study discontinuous percolation transitions (PTs) in the diffusion-limited cluster aggregation model of the sol-gel transition as an example of real physical systems, in which the number of aggregation events is regarded as the number of bonds occupied in the system. When particles are Brownian, in which cluster velocity depends on cluster size as vs˜s? with ?=-0.5, a larger cluster has less probability to collide with other clusters because of its smaller mobility. Thus, the cluster is effectively more suppressed in growth of its size. Then the giant cluster size increases drastically by merging those suppressed clusters near the percolation threshold, exhibiting a discontinuous PT. We also study the tricritical behavior by controlling the parameter ?, and the tricritical point is determined by introducing an asymmetric Smoluchowski equation.

Cho, Y. S.; Kahng, B.

2011-11-01

132

Localization and percolation in random elastic networks  

NASA Astrophysics Data System (ADS)

We consider a minimal model for a disordered phonon system that shows rich behavior in the localization properties of the phonons. We use a percolation analysis to argue for a localization/delocalization transition of the phonon modes and predict the speed of sound in the delocalized region, with comparison to numerics. We show that in contrast to the behavior in electronic systems (cf. Anderson localization), the transition exists for arbitrarily large disorder, albeit with an exponentially small critical frequency. The structure of the modes reflects a divergent percolation length that arises from the disorder in the springs without being explicitly present in the definition of our model. We calculate the critical frequency as a function of density and test the prediction numerically using a recursive Green function method. We further explore the existence of delocalized states in the two-dimensional version of this model.

Krich, Jacob; Amir, Ariel; Vitelli, Vincenzo; Oreg, Yuval; Imry, Yoseph

2013-03-01

133

Percolation transition in nanowire magnetorheological fluids  

NASA Astrophysics Data System (ADS)

We measure the yield stress of magnetorheological (MR) fluids that employ cobalt nanowires as the ferromagnetic component and observe a percolation transition in the yield stress at a critical value of the cobalt-nanowire volume fraction, pc. The critical volume fraction depends not only on the particle size and aspect ratio (as expected) but also on the external magnetic field applied to the MR-fluid sample. We fit the yield-stress data using McLachlan's generalized effective medium (GEM) model to determine pc and the percolation exponents s and t that describe the transition behavior below and above pc, respectively. The phase transition from low- to high-yield stress at low magnetic-particle volume fraction (<1% ) has potential application to the development of precision magnetic sensors and actuators.

Karli, Josh; Zimmerman, Darin; Filer, Joseph; Bell, Richard; Wereley, Norman

2009-03-01

134

Conformal invariance in two-dimensional percolation  

Microsoft Academic Search

The immediate purpose of the paper was neither to review the basic\\u000adefinitions of percolation theory nor to rehearse the general physical notions\\u000aof universality and renormalization (an important technique to be described in\\u000aPart Two). It was rather to describe as concretely as possible, although in\\u000ahypothetical form, the geometric aspects of universality, especially conformal\\u000ainvariance, in the context

Robert Langlands; Philippe Pouliot; Yvan Saint-Aubin

1994-01-01

135

A biological semiconductor based on electrical percolation  

PubMed Central

We have developed a novel biological semiconductor (BSC) based on electrical percolation through a multi-layer 3-D carbon nanotube-antibody network, which can measure biological interactions directly and electronically. In Electrical Percolation, the passage of current through the conductive network is dependent upon the continuity of the network. Molecular interactions, such as binding of antigens to the antibodies, disrupt the network continuity causing increased resistance of the network. A BSC is fabricated by immobilizing a pre-functionalized single-walled carbon nanotubes (SWNTs)-antibody complex directly on a Poly(methyl methacrylate) (PMMA) surface (also known as plexi-glass or Acrylic). We used the BSC for direct (label-free) electronic measurements of antibody-antigen binding, showing that, at slightly above the electrical percolation threshold of the network, binding of a specific antigen dramatically increases the electrical resistance. Using anti-Staphylococcal enterotoxin B (SEB) IgG as a “gate” and SEB as an “actuator”, we demonstrated that the BSC was able to detect SEB at concentrations of 1 ng/ml. The new BSCs may permit assembly of multiple sensors on the same chip to create “Biological Central Processing Units (CPUs)” with multiple biological elements, capable of processing and sorting out information on multiple analytes simultaneously.

Yang, Minghui; Bruck, Hugh Alan; Kostov, Yordan; Rasooly, Avraham

2010-01-01

136

Percolative phenomena in branched reverse micelles  

NASA Astrophysics Data System (ADS)

The role played by the solvation water molecules on the macroscopically observed sol-gel transition in lecithin/cyclohexane/water reverse micelles is investigated. The self-diffusion properties of both the surfactant and the water molecules entrapped in the micellar cores are investigated by quasi-elastic neutron scattering, while dielectric relaxation and conductivity measurements furnish information on the structural relaxation processes taking place in the system. The obtained results are compared with the experimental indications for AOT/cyclohexane/water systems. The data from lecithin-based systems can be interpreted only by assuming that, contrary to AOT systems, the water molecules are entrapped at the interfaces without coalescing into an inner water pool. Also, the charge transport mechanisms look very different in the two kinds of systems. In particular, in the case of lecithin, it is shown how the conductivity appears mainly due to inter-micellar bond percolation: it is suggested that the solvated water molecules can induce a change of the surface curvature, in such a way promoting the formation of branch points. The idea of the existence of a percolated network of branched cylindrical micelles agrees with the observed temperature dependence of the system conductivity. The study of the electrorheologic behavior of the system under electric field confirms the existence of a percolated transient network in the gel phase.

Aliotta, F.; Fazio, B.

2002-02-01

137

Contact percolation transition in athermal particulate systems  

NASA Astrophysics Data System (ADS)

Typical quasistatic compression algorithms for generating jammed packings of purely repulsive, frictionless particles begin with dilute configurations and then apply successive compressions with the relaxation of the elastic energy allowed between each compression step. It is well known that during isotropic compression these systems undergo a first-order-like jamming transition at packing fraction ?J from an unjammed state with zero pressure and no force-bearing contacts to a jammed, rigid state with nonzero pressure, a percolating network of force-bearing contacts, and contact number z=2d, where d is the spatial dimension. Using computer simulations of two-dimensional systems with monodisperse and bidisperse particle size distributions, we investigate the second-order-like contact percolation transition, which precedes the jamming transition with ?Ppercolation transition also signals the onset of a nontrivial mechanical response to applied stress. Our results show that cooperative particle motion occurs in unjammed systems significantly below the jamming transition for ?P?J.

Shen, Tianqi; O'Hern, Corey S.; Shattuck, M. D.

2012-01-01

138

Generic Rigidity Percolation in Two Dimensions  

NASA Astrophysics Data System (ADS)

We study rigidity percolation for random central-force networks, using the Pebble Game(D. J. Jacobs and M. F. Thorpe, Phys. Rev. Letts. 75), 4051 (1995) algorithm on the bond and site diluted generic triangular lattice. Here, each site location is randomly displaced from the perfect lattice, removing any special symmetries. The total number of floppy modes are counted exactly, and exhibit a cusp singularity in the second derivative of the number of floppy modes, at the transition from a rigid to a floppy structure. The critical thresholds for bond and site dilution are found to be 0.6602 ± 0.0003 and 0.6976 ± 0.0003 respectively. We find that the generic rigidity percolation transition is second order, but in a different universality class than connectivity percolation, with the exponents; ? = -0.48 ± 0.05 , ? = 0.175 ± 0.02 and ? = 1.21 ± 0.06 . The fractal dimension of the spanning rigid clusters and the spanning stressed regions at the critical threshold are found to be df = 1.86 ± 0.02 and d_BB = 1.80 ± 0.03 respectively. Some elastic properties of the rigid backbone will be discussed.

Thorpe, M. F.; Jacobs, D. J.; Day, A. R.

1996-03-01

139

Sequential algorithm for fast clique percolation  

NASA Astrophysics Data System (ADS)

In complex network research clique percolation, introduced by Palla, Derényi, and Vicsek [Nature (London) 435, 814 (2005)], is a deterministic community detection method which allows for overlapping communities and is purely based on local topological properties of a network. Here we present a sequential clique percolation algorithm (SCP) to do fast community detection in weighted and unweighted networks, for cliques of a chosen size. This method is based on sequentially inserting the constituent links to the network and simultaneously keeping track of the emerging community structure. Unlike existing algorithms, the SCP method allows for detecting k -clique communities at multiple weight thresholds in a single run, and can simultaneously produce a dendrogram representation of hierarchical community structure. In sparse weighted networks, the SCP algorithm can also be used for implementing the weighted clique percolation method recently introduced by Farkas [New J. Phys. 9, 180 (2007)]. The computational time of the SCP algorithm scales linearly with the number of k -cliques in the network. As an example, the method is applied to a product association network, revealing its nested community structure.

Kumpula, Jussi M.; Kivelä, Mikko; Kaski, Kimmo; Saramäki, Jari

2008-08-01

140

Recycle Used Oil on America Recycles Day.  

ERIC Educational Resources Information Center

Explains that motor oils can be reused and recycled. Educates students about environmental hazards and oil management and includes classroom activities. Addresses the National Science Education Standards. (YDS)

White, Boyd W.

2000-01-01

141

Recycled Art: Create Puppets Using Recycled Objects.  

ERIC Educational Resources Information Center

Presents an activity from "Healthy Foods from Healthy Soils" for making puppets using recycled food packaging materials. Includes background information, materials, instructions, literature links, resources, and benchmarks. (NB)

Clearing, 2003

2003-01-01

142

The Ammonia-Soda Process.  

ERIC Educational Resources Information Center

This article is a condensed version of a commentary written to accompany a set of slides which describes the ammonia-soda process used by the ammonia-soda plant at Northwich of the United Kingdom. (HM)

Tingle, M.

1979-01-01

143

The Chemistry of Liquid Ammonia.  

ERIC Educational Resources Information Center

The solvent and chemical properties of liquid ammonia are presented. In a certain sense, ammonia is a more versatile solvent than is water because of its ability to solubilize, without reaction, highly negative or reducing species. (Author/BB)

Lagowski, J. J.

1978-01-01

144

Liberation of ammonia by cyanobacteria  

SciTech Connect

Photoheterotrophic nitrogen-fixing cyanobacteria release ammonia when treated with methionine sulfoximine (MSX) to inhibit nitrogen incorporation into protein. This released ammonia can be derived from recently fixed nitrogen (nitrogen atmosphere) or endogenous reserves (argon atmosphere). Anaerobic ammonia release requires light and is stimulated by the photosystem II herbicides DCMU and Atrazine, regardless of the source of ammonia. As much as one quarter of the total cellular nitrogen can be released as ammonia by cyanbacteria treated with MSX and DCMU under argon in light. Chromatography of cell extracts indicates that virtually all cellular proteins are degraded. DCMU and Atrazine, at very low concentration, inhibit sustained uptake of the ammonia analog /sup 14/C methylamine. These data indicate that the herbicides interrupt ammonia uptake and retention by the cells, and support a role for photosystem II in ammonia metabolism.

Newton, J.W.

1986-04-01

145

Percolation behavior in metallic-insulator composite systems and the filling factor near the percolation threshold  

NASA Astrophysics Data System (ADS)

We investigate the percolation behavior in various composite metal -- insulator systems including LiCoO2/ CrO2, MgB2/Al2O3, CrO2/Al2O3, CrO2/ CaCO3. The effect of particle size and shapes in these systems has been studied to better understand the geometrical phase transitions. The power law exponent around the percolation threshold has been found to be 2.0±0.04 in all the cases, which agrees well with the theoretical result. Interestingly, the filling factor of these composite systems also exhibits the power law dependence near the percolation threshold with the value found to be dependent on the shape of the insulating particle. The exponent ranges from 0.2 to 0.4 depending on size of particles of a given shape in the composite system.

Mukherjee, Rupam; Mishra, Debabrata; Huang, Zhifeng; Nadgorny, Boris

2012-10-01

146

Integrated optic ammonia sensor  

Microsoft Academic Search

Most of the disadvantages that exist with electrochemical devices (e.g., short lifetimes, difficult to miniaturize, need of reference electrodes) can be avoided by using optical sensors. Smock et al. describe a device incorporating a ninhydrin coated fused silica rod that could detect ammonia vapor at concentrations below 100 ppb, however, the reaction is irreversible. Guiliani et al. describe a reversible

Rainer Klein; Edgar I. Voges

1993-01-01

147

Continuum percolation of carbon nanotubes in polymeric and colloidal media  

PubMed Central

We apply continuum connectedness percolation theory to realistic carbon nanotube systems and predict how bending flexibility, length polydispersity, and attractive interactions between them influence the percolation threshold, demonstrating that it can be used as a predictive tool for designing nanotube-based composite materials. We argue that the host matrix in which the nanotubes are dispersed controls this threshold through the interactions it induces between them during processing and through the degree of connectedness that must be set by the tunneling distance of electrons, at least in the context of conductivity percolation. This provides routes to manipulate the percolation threshold and the level of conductivity in the final product. We find that the percolation threshold of carbon nanotubes is very sensitive to the degree of connectedness, to the presence of small quantities of longer rods, and to very weak attractive interactions between them. Bending flexibility or tortuosity, on the other hand, has only a fairly weak impact on the percolation threshold.

Kyrylyuk, Andriy V.; van der Schoot, Paul

2008-01-01

148

Percolation in a Proton Exchange Membrane Fuel Cell Catalyst Layer  

SciTech Connect

Water management in the catalyst layers of proton exchange membrane fuel cells (PEMFC) is confronted by two issues, flooding and dry out, both of which result in improper functioning of the fuel cell and lead to poor performance and degradation. At the present time, the data that has been reported about water percolation and wettability within a fuel cell catalyst layer is limited. A method and apparatus for measuring the percolation pressure in the catalyst layer has been developed based upon an experimental apparatus used to test water percolation in porous transport layers (PTL). The experimental setup uses a pseudo Hele-Shaw type testing where samples are compressed and a fluid is injected into the sample. Testing the samples gives percolation pressure plots which show trends in increasing percolation pressure with an increase in flow rate. A decrease in pressure was seen as percolation occurred in one sample, however the pressure only had a rising effect in the other sample.

Stacy, Stephen; Allen, Jeffrey

2012-07-01

149

Recycling Rules: Understanding Recycling and a MRF  

NSDL National Science Digital Library

In this activity, learners simulate the separation techniques that materials recovery facilities (MRFs) use and then design their own series of recycling techniques. Learners identify four ways recyclable materials can be separated and sorted at a MRF: conveyor belts, blowers, flotation, and magnetism.

Keep America Beautiful, Inc.

2010-01-01

150

Sharpness of the phase transition in percolation models  

Microsoft Academic Search

The equality of two critical points — the percolation thresholdpH and the pointpT where the cluster size distribution ceases to decay exponentially — is proven for all translation invariant independent percolation models on homogeneousd-dimensional lattices (d?1). The analysis is based on a pair of new nonlinear partial differential inequalities for an order parameterM(?,h), which forh=0 reduces to the percolation densityP?

Michael Aizenman; David J. Barsky

1987-01-01

151

Newell's metals recycling tradition  

Microsoft Academic Search

Since 1976, Newell Recycling Co., Inc.'s metals recycling facility in Atlanta has been processing everything from aluminum cans to automobiles. It is a full-service metals recycling center, handling both ferrous and non-ferrous metals. Newell Recycling takes metal components and machinery and processes it into usable feedstock for metal smelters and steel mills. The facility is split into five basic processing

Dabaie

1994-01-01

152

Correction-to-scaling exponent for two-dimensional percolation  

SciTech Connect

We show that the correction-to-scaling exponents in two-dimensional percolation are bounded by {Omega}{<=}72/91, {omega}=D{Omega}{<=}3/2, and {Delta}{sub 1}={nu}{omega}{<=}2, based upon Cardy's result for the crossing probability on an annulus. The upper bounds are consistent with many previous measurements of site percolation on square and triangular lattices and new measurements for bond percolation, suggesting that they are exact. They also agree with exponents for hulls proposed recently by Aharony and Asikainen, based upon results of den Nijs. A corrections scaling form evidently applicable to site percolation is also found.

Ziff, Robert M. [Center for the Study of Complex Systems and Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2011-02-15

153

Percolation and critical exponents for the viscosity of microemulsions  

NASA Astrophysics Data System (ADS)

The study of the viscosity of waterless microemulsions glycerol-AOT-isooctane [where AOT represents sodium bis(2-ethylhexyl) sulfosuccinate] shows that there is a quantitative agreement between experimental values and percolation theory. The values of the scaling exponents ?'=2.00+/-0.25 and s'=1.20+/-0.20 for viscosity are very close of those of conductivity obtained for dynamical percolation with water-AOT-oil systems. The water-AOT-oil and glycerol-AOT-oil microemulsions behave in a broadly similar way as regards dynamic percolation provided that the conditions of application of the percolation laws are satisfied.

Saidi, Z.; Mathew, C.; Peyrelasse, J.; Boned, C.

1990-07-01

154

Connectedness Percolation of Elongated Hard Particles in an External Field  

NASA Astrophysics Data System (ADS)

A theory is presented of how orienting fields and steric interactions conspire against the formation of a percolating network of, in some sense, connected elongated colloidal particles in fluid dispersions. We find that the network that forms above a critical loading breaks up again at higher loadings due to interaction-induced enhancement of the particle alignment. Upon approach of the percolation threshold, the cluster dimensions diverge with the same critical exponent parallel and perpendicular to the field direction, implying that connectedness percolation is not in the universality class of directed percolation.

Otten, Ronald H. J.; van der Schoot, Paul

2012-02-01

155

Recycling of automotive aluminum  

Microsoft Academic Search

With the global warming of concern, the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive because of its economic and environmental benefits. In this work, recycling of automotive aluminum is reviewed to highlight environmental benefits of aluminum recycling, use of aluminum alloys in automotive applications, automotive recycling process, and new technologies in

Jirang CUI; Hans J. ROVEN

2010-01-01

156

Limits of Metal Recycling  

Microsoft Academic Search

This work points out different limits for the metal recycling of aluminium, copper and zinc. Being the most important parameter of the recycling activities of every metal, the scrap availability is focused on by the discussion. Knowing the availability of secondary raw materials in an existing system, the respective recycled metal content of production can be determined. However, this varies

Georg Rombach; RWTH Aachen

157

The future of recycling  

Microsoft Academic Search

Recycling in general and metal recycling in particular, many believe, enjoy a very bright future. As resource depletion, environmental concerns, and other factors drive primary production costs up, the relative importance of recycling in supplying the material needs of society will grow. This optimistic view, however, may paint an overly rosy and misleading picture.A large portion of secondary metal production

John E. Tilton

1999-01-01

158

Percolation of interdependent networks with intersimilarity  

NASA Astrophysics Data System (ADS)

Real data show that interdependent networks usually involve intersimilarity. Intersimilarity means that a pair of interdependent nodes have neighbors in both networks that are also interdependent [Parshani Europhys. Lett.EULEEJ0295-507510.1209/0295-5075/92/68002 92, 68002 (2010)]. For example, the coupled worldwide port network and the global airport network are intersimilar since many pairs of linked nodes (neighboring cities), by direct flights and direct shipping lines, exist in both networks. Nodes in both networks in the same city are regarded as interdependent. If two neighboring nodes in one network depend on neighboring nodes in the other network, we call these links common links. The fraction of common links in the system is a measure of intersimilarity. Previous simulation results of Parshani suggest that intersimilarity has considerable effects on reducing the cascading failures; however, a theoretical understanding of this effect on the cascading process is currently missing. Here we map the cascading process with intersimilarity to a percolation of networks composed of components of common links and noncommon links. This transforms the percolation of intersimilar system to a regular percolation on a series of subnetworks, which can be solved analytically. We apply our analysis to the case where the network of common links is an Erd?s-Rényi (ER) network with the average degree K, and the two networks of noncommon links are also ER networks. We show for a fully coupled pair of ER networks, that for any K?0, although the cascade is reduced with increasing K, the phase transition is still discontinuous. Our analysis can be generalized to any kind of interdependent random network systems.

Hu, Yanqing; Zhou, Dong; Zhang, Rui; Han, Zhangang; Rozenblat, Céline; Havlin, Shlomo

2013-11-01

159

Percolation of interdependent networks with intersimilarity.  

PubMed

Real data show that interdependent networks usually involve intersimilarity. Intersimilarity means that a pair of interdependent nodes have neighbors in both networks that are also interdependent [Parshani et al. Europhys. Lett. 92, 68002 (2010)]. For example, the coupled worldwide port network and the global airport network are intersimilar since many pairs of linked nodes (neighboring cities), by direct flights and direct shipping lines, exist in both networks. Nodes in both networks in the same city are regarded as interdependent. If two neighboring nodes in one network depend on neighboring nodes in the other network, we call these links common links. The fraction of common links in the system is a measure of intersimilarity. Previous simulation results of Parshani et al. suggest that intersimilarity has considerable effects on reducing the cascading failures; however, a theoretical understanding of this effect on the cascading process is currently missing. Here we map the cascading process with intersimilarity to a percolation of networks composed of components of common links and noncommon links. This transforms the percolation of intersimilar system to a regular percolation on a series of subnetworks, which can be solved analytically. We apply our analysis to the case where the network of common links is an Erd?s-Rényi (ER) network with the average degree K, and the two networks of noncommon links are also ER networks. We show for a fully coupled pair of ER networks, that for any K?0, although the cascade is reduced with increasing K, the phase transition is still discontinuous. Our analysis can be generalized to any kind of interdependent random network systems. PMID:24329316

Hu, Yanqing; Zhou, Dong; Zhang, Rui; Han, Zhangang; Rozenblat, Céline; Havlin, Shlomo

2013-11-01

160

Spin Glasses at the Bond Percolation Threshold  

NASA Astrophysics Data System (ADS)

Low energy excitations for the Edwards-Anderson model on hyper- cubic lattices at the bond percolation threshold pc are investigated. At T=0, pc separates paramagnetic and spin glass phases. At the ``edge'' of the ordered state, these excitations are characterized by a distinct scaling exponent. This exponent allows to determine the shape of the phase boundary, Tc(p)˜(p-pc)^?, for p->pc^+, which is experimentally measurable in d=3. At pc, very large spin glass systems can be studied with an exact reduction algorithm to produce accurate scaling behavior. For more information, see http://www.physics.emory.edu/faculty/boettcher/ Europhys. Lett. 67, 453 (2004)

Marchetti, Emiliano; Boettcher, Stefan

2006-03-01

161

Granular collapse as a percolation transition.  

PubMed

Inelastic collapse is found in a two-dimensional system of inelastic hard disks confined between two walls which act as an energy source. As the coefficient of restitution is lowered, there is a transition between a state containing small collapsed clusters and a state dominated by a large collapsed cluster. The transition is analogous to that of a percolation transition. At the transition the number of clusters n(s) of size s scales as n(s) approximately s(-tau) with tau approximately equal to 2.7. PMID:11970654

Tobochnik, J

1999-12-01

162

Bounds of percolation thresholds on hyperbolic lattices  

NASA Astrophysics Data System (ADS)

We analytically study bond percolation on hyperbolic lattices obtained by tiling a hyperbolic plane with constant negative Gaussian curvature. The quantity of our main concern is pc2, the value of occupation probability where a unique unbounded cluster begins to emerge. By applying the substitution method to known bounds of the order-5 pentagonal tiling, we show that pc2?0.382508 for the order-5 square tiling, pc2?0.472043 for its dual, and pc2?0.275768 for the order-5-4 rhombille tiling.

Lee, Junghoon F.; Baek, Seung Ki

2012-12-01

163

Percolation in multiplex networks with overlap  

NASA Astrophysics Data System (ADS)

From transportation networks to complex infrastructures, and to social and communication networks, a large variety of systems can be described in terms of multiplexes formed by a set of nodes interacting through different networks (layers). Multiplexes may display an increased fragility with respect to the single layers that constitute them. However, so far the overlap of the links in different layers has been mostly neglected, despite the fact that it is an ubiquitous phenomenon in most multiplexes. Here, we show that the overlap among layers can improve the robustness of interdependent multiplex systems and change the critical behavior of the percolation phase transition in a complex way.

Cellai, Davide; López, Eduardo; Zhou, Jie; Gleeson, James P.; Bianconi, Ginestra

2013-11-01

164

Modied invasion percolation model for fracking  

NASA Astrophysics Data System (ADS)

Recent developments in hydraulic fracturing (fracking) have enabled the recovery of large reserves of natural gas and oil. These developments include a change from low-volume, high-viscosity fluid injection to high-volume, low-viscosity injection. We consider new models of Invasion Percolation, (IP) which are models that were originally introduced to represent the injection of an invading fluid into a fluid filled porous medium. A primary difference between our model and the original model is the elimination of any unbroken bonds whose end sites are both filled with fluid. While the original model was found to have statistics nearly identical to traditional percolation, we find significant statistical differences. In particular, the distribution of broken bond strengths displays a strong roll-over near the critical point. Another difference between traditional percolation clusters and clusters generated using our model is the absence of internal loops. The modified growth rule prevents the formation of internal loops making the growing cluster ramified. Other ramified networks include drainage basins and DLA clusters. The study of drainage basins led to the development of Horton-Strahler and Tokunaga network statistics. We used both Horton-Strahler and Tokunaga network statistics to characterize simulated clusters using and found that the clusters generated by our model are statistically self-similar fractals. In addition to fractal clusters, IP also displays burst dynamics, in which the cluster extends rapidly through a spontaneous extension of percolating bonds. We define a burst to be a consecutive series of broken bonds whose strengths are all below a specified value. Using this definition of bursts we found good agreement with a power-law frequency-area distribution. Our model displays many of the characteristics of an energy landscape, and shows many similarities to DLA, neural networks, ecological landscapes, and the world wide web. We anticipate that this new class of models will have broad applicability to the study of instabilities in high dimensional complex networks, a topic of considerable interest across a wide array of fields.

Norris, J.; Turcotte, D. L.; Rundle, J. B.

2013-12-01

165

PRETREATMENT OF CORN STOVER BY SOAKING IN AQUEOUS AMMONIA PERCOLATION PROCESS. (R831645)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

166

A rationale for recycling  

NASA Astrophysics Data System (ADS)

The decision as to whether to recycle discarded objects or not has traditionally been made on a simple financial basis. However, over the last few years a popular movement has sprung up which regards recycling as a good in itself, and this movement finds itself at odds with the present financial basis for recycling. In this paper a rationale for recycling is worked out in an attempt to resolve this conflict. It is concluded that the normal market signals do not provide a proper basis for recycling decisions and that this market failure must be corrected by government intervention. However, this intervention should not take the form of uncritical support for recycling. Rather the societal objectives of individual recycling proposals should be identified and the proposal should then be evaluated in terms of whether it would achieve these objectives more effectively than some alternative action.

Evans, David G.

1994-05-01

167

Micro ammonia sensor  

SciTech Connect

A micro ammoniasensor, consisting of an ISFET covered with a dry membrane which is made from nonactin and substituted poly-..gamma..-methyl-L-glutamate (PMG) is described. The gate output voltage of the micro ammonia sensor increased with NH/sub 4/OH addition. The response time of the sensor was 2 min at 30/sup 0/C, and the sensor exhibited superior selectivity for NH/sub 4//sup +/ compared to a pH sensitive ISFET.

Kubo, I.; Karube, I.; Moriizumi, T.

1986-01-01

168

Spectral Dimension of a Percolation Network  

NASA Astrophysics Data System (ADS)

While the fractal dimension df describes the self-similar static nature of the lattice, the spectral dimension ds dictates the dynamic properties on it. Alexander and Orbach^1 conjectured that the spectral dimension might be exactly 4/3 for percolation networks with embedding euclidian dimension de >= 2. Recent numerical simulations^2, however, could not decisively prove or disprove this conjecture, although there are other indirect evidences that it is true. We believe that the failure of the simulations to decisively check the validity of the conjecture is due to the non-stochastic nature of the methods. Most of these simulations are Monte Carlo Methods based on a random-walk model and, in spite of very large number of walks on huge lattices, the results do not reach the satisfactory level. In this work we apply a stochastic approach^3 to determine the spectral dimension of percolation network for de >= 2 and check the validity of the Alexander-Orbach-conjecture. Due to its stochastic nature this method is numerically superior and more accurate than the conventional Monte Carlo simulations. References: 1. S. Alexander and R. Orbach, J. Phys. Lett. (Paris) 43 (1982) L625. 2. N. Pitsianis, G. Bleris and P. Argyrakis, Phys. Rev. B 39 (1989) 7097. 3. J. Rudra and J. Kozak, Phys. Lett A 151 (1990) 429.

Rudra, Jayanta

2005-03-01

169

Percolation experiments in complex fractal media  

NASA Astrophysics Data System (ADS)

Series of flow percolation experiments under gravity were performed in different glass model and real karstic media samples. We present a multifractal characterization of the experiments in several parametric non-dimensional flow descriptors. Using the maximum local multifractal dimension as an additional flow indicator. Also experiments on Non laminar flow and transport conditions in fractured and karstified media were performed at Bari. The investigation on hypothesis of non linear flow and non fickian transport in fractured aquifers led to a distinction on the different role of channels and microchannels and of the presence of vortices and eddy trapping. The dominance of the elongated channels produced early arrival times, with the solute traveling along the high velocity channel network. On the other hand in a lumped structured karstic media, the percolation flow produced long tails with local Eddy mixing, entrapment in eddies, and slow flow out of the eddies. In The laboratory experiments performed in Madrid and in DAMTP Cambridge the role of the initial pressure produced fractal pathway structures even in iniatilly uniform ballotini substrates.

Redondo, Jose Manuel; Tarquis, Ana Maria; Cherubini, Claudia; Lopez Gzlez-Nieto, Pilar; Vila, Teresa

2013-04-01

170

Percolation on bipartite scale-free networks  

NASA Astrophysics Data System (ADS)

Recent studies introduced biased (degree-dependent) edge percolation as a model for failures in real-life systems. In this work, such process is applied to networks consisting of two types of nodes with edges running only between nodes of unlike type. Such bipartite graphs appear in many social networks, for instance in affiliation networks and in sexual-contact networks in which both types of nodes show the scale-free characteristic for the degree distribution. During the depreciation process, an edge between nodes with degrees k and q is retained with a probability proportional to (, where ? is positive so that links between hubs are more prone to failure. The removal process is studied analytically by introducing a generating functions theory. We deduce exact self-consistent equations describing the system at a macroscopic level and discuss the percolation transition. Critical exponents are obtained by exploiting the Fortuin-Kasteleyn construction which provides a link between our model and a limit of the Potts model.

Hooyberghs, H.; Van Schaeybroeck, B.; Indekeu, J. O.

2010-08-01

171

Plasmonic percolation: plasmon-manifested dielectric-to-metal transition.  

PubMed

Percolation generally refers to the phenomenon of abrupt variations in electrical, magnetic, or optical properties caused by gradual volume fraction changes of one component across a threshold in bicomponent systems. Percolation behaviors have usually been observed in macroscopic systems, with most studies devoted to electrical percolation. We report on our observation of plasmonic percolation in Au nanorod core-Pd shell nanostructures. When the Pd volume fraction in the shell consisting of palladium and water approaches the plasmonic percolation threshold, ~70%, the plasmon of the nanostructure transits from red to blue shifts with respect to that of the unshelled Au nanorod. This plasmonic percolation behavior is also confirmed by the scattering measurements on the individual core-shell nanostructures. Quasistatic theory and numerical simulations show that the plasmonic percolation originates from a positive-to-negative transition in the real part of the dielectric function of the shell as the Pd volume fraction is increased. The observed plasmonic percolation is found to be independent of the metal type in the shell. Moreover, compared to the unshelled Au nanorods with similar plasmon wavelengths, the Au nanorod core-Pd shell nanostructures exhibit larger refractive index sensitivities, which is ascribed to the expulsion of the electric field intensity from the Au nanorod core by the adsorbed Pd nanoparticles. PMID:22757659

Chen, Huanjun; Wang, Feng; Li, Kun; Woo, Kat Choi; Wang, Jianfang; Li, Quan; Sun, Ling-Dong; Zhang, Xixiang; Lin, Hai-Qing; Yan, Chun-Hua

2012-08-28

172

Electrically Percolating Clusters in Sheared Carbon Nanotube Composites  

NASA Astrophysics Data System (ADS)

The electrical conductivity of polymer nanotube composites can be dramatically modified by processing flows and subsequent annealing. The mechanism is widely believed to be nanotube structural rearrangements that occur during flow and alter the percolating pathways. We seek to directly visualize these flow-induced three-dimensional percolating clusters through three-dimensional confocal microscopy and image analysis.

Migler, Kalman; Moon, Doyoung; Obrzut, Jan; Douglas, Jack; Lam, Thomas; Sharma, Renu; Liddle, Alex James

2013-03-01

173

A chemical percolation model for coal devolatilization: Milestone report  

Microsoft Academic Search

The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated coal based on the chemical structure of the parent coal. This document provides complete details of the development of the CPD model. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the

T. H. Fletcher; A. R. Kerstein; R. J. Pugmire; M. Solum; D. M. Grant

1992-01-01

174

The abundance threshold for plague as a critical percolation phenomenon  

Microsoft Academic Search

Percolation theory is most commonly associated with the slow flow of liquid through a porous medium, with applications to the physical sciences. Epidemiological applications have been anticipated for disease systems where the host is a plant or volume of soil, and hence is fixed in space. However, no natural examples have been reported. The central question of interest in percolation

S. A. Davis; P. Trapman; H. Leirs; M. Begon; J. A. P. Heesterbeek

2008-01-01

175

Nanoscale Phase Coexistence and Percolative Quantum Transport  

NASA Astrophysics Data System (ADS)

We study the nanoscale phase coexistence of ferromagnetic metallic and antiferromagnetic insulating (AFI) regions by including the effect of AF superexchange and weak disorder in the double exchange model. We use a new Monte Carlo technique, mapping on the disordered spin-fermion problem to an ef­fective short range spin model, with self-consistently computed exchange constants. We recover “clus­ter coexistence” as seen earlier in exact simulation of small systems. The much larger sizes, ˜32×32, accessible with our technique, allow us to study the cluster pattern for varying electron density, disorder, and temperature. We track the magnetic structure, obtain the density of states, with its “pseudogap” features, and, for the first time, provide a fully microscopic estimate of the resistivity in a phase coexistence regime, comparing it with the “percolation” scenario.

Kumar, Sanjeev; Majumdar, Pinaki

2004-03-01

176

Nanoscale phase coexistence and percolative quantum transport.  

PubMed

We study the nanoscale phase coexistence of ferromagnetic metallic and antiferromagnetic insulating (AFI) regions by including the effect of AF superexchange and weak disorder in the double exchange model. We use a new Monte Carlo technique, mapping on the disordered spin-fermion problem to an effective short range spin model, with self-consistently computed exchange constants. We recover "cluster coexistence" as seen earlier in exact simulation of small systems. The much larger sizes, approximately 32 x 32, accessible with our technique, allow us to study the cluster pattern for varying electron density, disorder, and temperature. We track the magnetic structure, obtain the density of states, with its "pseudogap" features, and, for the first time, provide a fully microscopic estimate of the resistivity in a phase coexistence regime, comparing it with the "percolation" scenario. PMID:15089694

Kumar, Sanjeev; Majumdar, Pinaki

2004-03-26

177

Bootstrap Percolation in Living Neural Networks  

NASA Astrophysics Data System (ADS)

Recent experimental studies of living neural networks reveal that their global activation induced by electrical stimulation can be explained using the concept of bootstrap percolation on a directed random network. The experiment consists in activating externally an initial random fraction of the neurons and observe the process of firing until its equilibrium. The final portion of neurons that are active depends in a non linear way on the initial fraction. The main result of this paper is a theorem which enables us to find the final proportion of the fired neurons, in the asymptotic case, in the case of random directed graphs with given node degrees as the model for interacting network. This gives a rigorous mathematical proof of a phenomena observed by physicists in neural networks.

Amini, Hamed

2010-11-01

178

Limited path percolation in complex networks.  

PubMed

We study the stability of network communication after removal of a fraction q=1-p of links under the assumption that communication is effective only if the shortest path between nodes i and j after removal is shorter than al(ij)(a> or =1) where l(ij) is the shortest path before removal. For a large class of networks, we find analytically and numerically a new percolation transition at p(c)=(kappa(0)-1)((1-a)/a), where kappa(0) [triple bond] / and k is the node degree. Above p(c), order N nodes can communicate within the limited path length al(ij), while below p(c), N(delta) (delta<1) nodes can communicate. We expect our results to influence network design, routing algorithms, and immunization strategies, where short paths are most relevant. PMID:17995444

López, Eduardo; Parshani, Roni; Cohen, Reuven; Carmi, Shai; Havlin, Shlomo

2007-11-01

179

Line of percolation in supercritical water  

NASA Astrophysics Data System (ADS)

The percolation transition of the hydrogen-bonded clusters of molecules is investigated in supercritical water by Monte Carlo computer simulations. Simulations have been performed at four thermodynamic state points located above the supercritical extension of the vapor-liquid coexistence curve on the p-T phase diagram and at four state points located below this curve. It is found in a temperature range of a few hundred Kelvin that the extension of the vapor-liquid coexistence curve separates the supercritical thermodynamic states in which the water molecules form infinite hydrogen-bonded clusters from those in which the hydrogen-bonded clusters are isolated oligomers. However, the difference between the size of the hydrogen-bonded clusters at thermodynamic states located at the two sides of the extension of the coexistence curve is found to decrease with increasing temperature, and the present results suggest that this difference is likely to vanish at high enough temperatures.

Pártay, Lívia; Jedlovszky, Pál

2005-07-01

180

Line of percolation in supercritical water.  

PubMed

The percolation transition of the hydrogen-bonded clusters of molecules is investigated in supercritical water by Monte Carlo computer simulations. Simulations have been performed at four thermodynamic state points located above the supercritical extension of the vapor-liquid coexistence curve on the p-T phase diagram and at four state points located below this curve. It is found in a temperature range of a few hundred Kelvin that the extension of the vapor-liquid coexistence curve separates the supercritical thermodynamic states in which the water molecules form infinite hydrogen-bonded clusters from those in which the hydrogen-bonded clusters are isolated oligomers. However, the difference between the size of the hydrogen-bonded clusters at thermodynamic states located at the two sides of the extension of the coexistence curve is found to decrease with increasing temperature, and the present results suggest that this difference is likely to vanish at high enough temperatures. PMID:16050754

Pártay, Lívia; Jedlovszky, Pál

2005-07-01

181

Atmospheric Dispersion of Ammonia: An Ammonia Fog Model.  

National Technical Information Service (NTIS)

A simplification to the two-phase ammonia vapor-droplet fog problem has been implemented to study the dispersion of a spill of 40 tons of ammonia. We have circumvented the necessity of adding the partial differential equations for mass, momentum, and ener...

E. J. Kansa H. C. Rodean S. T. Chan D. L. Ermak

1983-01-01

182

Pressure-Saturation Curves and the Critical Volume Fraction for Percolation: Accessibility Function of Percolation Theory  

NASA Astrophysics Data System (ADS)

The pressure-saturation curves of porous media give fundamental information about the pore space. In equilibrium, ignoring effects due to hysteresis and pore accessibility, it should be possible to extract a pore-size distribution from h(?) data, as described in Chap. 3. However, a number of percolation effects complicate the analysis and make such a simple inference impossible. The pressure-saturation relation is affected by both the lack of continuity of the air phase near saturation and by a similar lack of continuity of the water phase near the dry end. Given that these effects are due to phase transitions (in the percolation sense), small changes in experimental conditions can produce major (and sometimes puzzling) changes in the results. Further, since the correlation length diverges near these transitions, numerical simulations under both wet and dry conditions are amenable to finite-size scaling analysis. Since the critical volume fractions for percolation of air and water are critical to the discussion, experimental evidence regarding these values is presented toward the end of this chapter.

Hunt, Allen; Ewing, Robert

183

Factors Influencing Household Recycling Behavior  

Microsoft Academic Search

To investigate factors encouraging or deterring recycling, telephone interviews were used to study recycling behavior, attitudes, and knowledge of 221 randomly selected adults in a suburban city that had begun a citywide curbside recycling program within the past year. Approximately 40% reported participation in the curbside recycling program, and nearly 20% more claimed that their household had been recycling in

Stuart Oskamp; Maura J. Harrington; Todd C. Edwards; Deborah L. Sherwood; Shawn M. Okuda; Deborah C. Swanson

1991-01-01

184

27 CFR 21.96 - Ammonia, aqueous.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Ammonia, aqueous. 21.96 Section 21...Specifications for Denaturants § 21.96 Ammonia, aqueous. (a) Alkalinity. Strongly alkaline to litmus. (b) Ammonia content. 27 to 30...

2013-04-01

185

Ambient Ammonia Measurements in Coastal Southeastern Virginia.  

National Technical Information Service (NTIS)

Results are presented from a measurement program to test an in situ ammonia measurement technique and to document the temporal and spatial variability associated with ammonia. The ammonia data were accumulated for two sites in coastal Southeastern Virgini...

C. N. Harward W. A. McClenny J. M. Hoell J. A. Williams B. S. Williams

1981-01-01

186

Process for removal of ammonia and acid gases from contaminated waters  

DOEpatents

Contaminating basic gases, i.e., ammonia, and acid gases, e.g., carbon dioxide, are removed from process waters or waste waters in a combined extraction and stripping process. Ammonia in the form of ammonium ion is extracted by an immiscible organic phase comprising a liquid cation exchange component, especially an organic phosphoric acid derivative, and preferably di-2-ethyl hexyl phosphoric acid, dissolved in an alkyl hydrocarbon, aryl hydrocarbon, higher alcohol, oxygenated hydrocarbon, halogenated hydrocarbon, and mixtures thereof. Concurrently, the acidic gaseous contaminants are stripped from the process or waste waters by stripping with steam, air, nitrogen, or the like. The liquid cation exchange component has the ammonia stripped therefrom by heating, and the component may be recycled to extract additional amounts of ammonia.

King, C. Judson (Kensington, CA); MacKenzie, Patricia D. (Berkeley, CA)

1985-01-01

187

Process for removal of ammonia and acid gases from contaminated waters  

DOEpatents

Contaminating basic gases, i.e., ammonia and acid gases, e.g., carbon dioxide, are removed from process waters or waste waters in a combined extraction and stripping process. Ammonia in the form of ammonium ion is extracted by an immiscible organic phase comprising a liquid cation exchange component, especially an organic phosphoric acid derivative, and preferably di-2-ethyl hexyl phosphoric acid, dissolved in an alkyl hydrocarbon, aryl hydrocarbon, higher alcohol, oxygenated hydrocarbon, halogenated hydrocarbon, and mixtures thereof. Concurrently, the acidic gaseous contaminants are stripped from the process or waste waters by stripping with stream, air, nitrogen, or the like. The liquid cation exchange component has the ammonia stripped therefrom by heating, and the component may be recycled to extract additional amounts of ammonia.

King, C.J.; Mackenzie, P.D.

1982-09-03

188

Ammonia caramels: Specifications and analysis  

Microsoft Academic Search

Twenty three UK commercially produced ammonia caramels and eight experimentally produced ammonia caramels have been analysed by a range of physical and chemical tests, which include solids content, nitrogen levels, colour intensity and pH. A statistical treatment of the results is reported.

A. L. Patey; G. Shearer; M. E. Knowles; W. H. B. Denner

1985-01-01

189

Ammonia caramels: specifications and analysis.  

PubMed

Twenty three UK commercially produced ammonia caramels and eight experimentally produced ammonia caramels have been analysed by a range of physical and chemical tests, which include solids content, nitrogen levels, colour intensity and pH. A statistical treatment of the results is reported. PMID:4018316

Patey, A L; Shearer, G; Knowles, M E; Denner, W H

1985-01-01

190

Elastic percolation transition in nanowire-based magnetorheological fluids  

NASA Astrophysics Data System (ADS)

We observe an elastic percolation transition in the yield stress (?y) of cobalt-nanowire magnetorheological fluids, with a critical volume fraction of ferromagnetic particles (pc) that increases with the applied magnetic field (H). Unlike studies of static percolation phenomena, our observations reveal percolation in a dynamic, fluid-semisolid system. The elastic critical exponent (f) appears to be independent of H, having a value in the range of 1.0-1.2, near that seen in various two-dimensional networks. The superelastic exponent (c) decreases with increasing H and is smaller than that seen in typical networks.

Zimmerman, D. T.; Bell, R. C.; Filer, J. A.; Karli, J. O.; Wereley, N. M.

2009-07-01

191

Equation of state of ammonia  

NASA Astrophysics Data System (ADS)

Ammonia and water are critical components of extraterrestrial bodies, determining the density and physical properties of the Outer Planets, their moons, and of extrasolar planets. Ammonia is unusual in having a high heat capacity relative to other molecular species. Equations of state (EOS) are presented for ammonia and for mixtures of ammonia and water. Their properties are discussed in terms of chemical compositions that evolve as pressure and temperature are varied. The NH4OH hydrate of ammonia is known to exist as a separate molecular species at pressures above about 5 GPa, and an effort was made to include reaction between NH3 and H2O in the mixture EOS. The EOS are suitable for calculating structures of icy planets and exoplanets, and of impacts. mass-radius relations which bound the possible interpretations of composition and structure for extraterrestrial bodies of unknown composition, such as exoplanets.

Mulford, R.; Swift, D. C.; Hamel, S.

2014-05-01

192

Recycling Conform Design.  

National Technical Information Service (NTIS)

The flow of materials in a real recycling system can be demonstrated in a simplified manner by a recycling model system. The analysis of this system results in additional new goals and guide lines for design. The guide lines are interpreted by examples sh...

W. Jorden

1984-01-01

193

Is mandated recycling possible  

Microsoft Academic Search

If piles of potentially recyclable materials are accumulated as a result of a mandatory source separation program, what options exist for the community First, it could attempt to market the recyclables through normal commercial channels. Second, the community could attempt to market the materials at lower prices to the consumers, since any contribution above available disposal cost is a profit

Cutler

1988-01-01

194

Partnership: Recycling $/$ Outdoor Education.  

ERIC Educational Resources Information Center

The Ottawa Board of Education (Ontario, Canada) has committed revenues generated by a districtwide recycling program to help fund the MacSkimming Outdoor Education Centre. A partnership between recycling and outdoor education is valuable in developing an environmental ethic among students and in finding new ways to fund outdoor education. (LP)

Weir, Phil

1996-01-01

195

Making Recycled Paper  

NSDL National Science Digital Library

This video and accompanying text describe the three-pronged resource conservation strategy known as "reduce, reuse, and recycle". The video segment, adapted from the television program 'ZOOM', features cast members demonstrating how something that might otherwise be discarded, such as newspaper, can be recycled to create a functional or even beneficial new product. Questions for discussion are also provided.

2005-01-01

196

Reuse, Reduce, Recycle.  

ERIC Educational Resources Information Center

Discussion of recycling paper in law libraries is also applicable to other types of libraries. Results of surveys of law libraries that investigated recycling practices in 1987 and again in 1990 are reported, and suggestions for reducing the amount of paper used and reusing as much as possible are offered. (LRW)

Briscoe, Georgia

1991-01-01

197

Recycling at Camp.  

ERIC Educational Resources Information Center

Outlines a Michigan summer camp's efforts to reduce solid waste disposal by recycling cardboard, tin, glass, aluminum, and plastic milk containers. Points out variables affecting the success of such efforts. Discusses Michigan state funding for the development of recycling programs. (SV)

Cummins, William M.

1988-01-01

198

Wee Recyclers Resources.  

ERIC Educational Resources Information Center

Hands-on activities in this guide are designed to help preschool children (ages 3-5) understand that reducing, reusing, and recycling preserves natural resources and prolongs the life of landfills. Children sort, match and compare recyclable items and learn to separate some items by number and color. The 29 activities are divided into units that…

Wisconsin State Dept. of Natural Resources, Madison.

199

The Fermilab recycler ring  

SciTech Connect

The Fermilab Recycler is a permanent magnet storage ring for the accumulation of antiprotons from the Antiproton Source, and the recovery and cooling of the antiprotons remaining at the end of a Tevatron store. It is an integral part of the Fermilab III luminosity upgrade. The following paper describes the design features, operational and commissioning status of the Recycler Ring.

Martin Hu

2001-07-24

200

AIRCRAFT INDUSTRY WASTEWATER RECYCLING  

EPA Science Inventory

The feasibility of recycling certain categories of water used in the manufacture of airplanes was demonstrated. Water in four categories was continuously recycled in 380-liter (100-gallon) treatment plants; chemical process rinse water, dye-penetrant crack-detection rinse water, ...

201

Advances in plastic recycling. Volume 1: Recycling of polyurethanes  

SciTech Connect

``Recycling of Polyurethanes'', the first volume in the Advances in Plastics Recycling series, is focused on the physical and chemical recycling of polyurethanes, with attention given to energy conversion. A compilation of the present ongoing studies on recycling of urethane and, in general, isocyanate-based polymers, the focus is on thermosetting urethane polymers. Contents include: Recycling of Polyurethane Plastics in the European Automotive Industry; Present State of Polyurethane Recycling in Europe; Processing Overview of Bonded Polyurethane Foam; Mechanical Recycling of Polyurethane Scrap; Ecostream{trademark}--A Technology Beyond Recycling; Recycling of Flexible polyurethane Foam; General purpose Adhesives Prepared from Chemically Recycled Waste Rigid Polyurethane Foams; and Utilization of Isocyanate Binders in Recycling of Scrap Automotive Headliners.

Frisch, K.C.; Klempner, D.; Prentice, G.

1999-07-01

202

Network robustness and fragility: percolation on random graphs.  

PubMed

Recent work on the Internet, social networks, and the power grid has addressed the resilience of these networks to either random or targeted deletion of network nodes or links. Such deletions include, for example, the failure of Internet routers or power transmission lines. Percolation models on random graphs provide a simple representation of this process but have typically been limited to graphs with Poisson degree distribution at their vertices. Such graphs are quite unlike real-world networks, which often possess power-law or other highly skewed degree distributions. In this paper we study percolation on graphs with completely general degree distribution, giving exact solutions for a variety of cases, including site percolation, bond percolation, and models in which occupation probabilities depend on vertex degree. We discuss the application of our theory to the understanding of network resilience. PMID:11136023

Callaway, D S; Newman, M E; Strogatz, S H; Watts, D J

2000-12-18

203

Double percolation transition in superconductor-ferromagnet nanocomposites.  

PubMed

A double percolation transition is identified in a binary network composed of nanoparticles of MgB2 superconductor and CrO2 half-metallic ferromagnet. Anomalously high-resistance or insulating state, as compared to the conducting or superconducting states in single-component systems of either constituent, is observed between two distinct percolation thresholds. This double percolation effect, which is especially pronounced at liquid helium temperatures, is controlled by composite volume fraction and originates from the suppressed interface conduction and tunneling as well as a large geometric disparity between nanoparticles of different species. We investigate the scaling behavior near both percolation thresholds and determine the distinct critical exponents associated with two different types of transitions. PMID:20366657

Liu, Xiangdong; Panguluri, Raghava P; Huang, Zhi-Feng; Nadgorny, Boris

2010-01-22

204

Double Percolation Transition in Superconductor/Ferromagnet Nanocomposites  

NASA Astrophysics Data System (ADS)

A double percolation transition is identified in a binary network composed of nanoparticles of MgB2 superconductor and CrO2 half-metallic ferromagnet. Anomalously high-resistance or insulating state, as compared to the conducting or superconducting states in single-component systems of either constituent, is observed between two distinct percolation thresholds. We investigate the scaling behavior near both percolation thresholds, and determine the distinct critical exponents associated with two different types of transitions. This double percolation effect, which is especially pronounced at liquid helium temperatures, is controlled by composite volume fraction and originates from the suppressed interface conduction and tunneling as well as a large geometric disparity between nanoparticles of different species. This sensitivity of the threshold to the geometry is confirmed by replacing CrO2 with LSMO particles of different size and shape, which results in significantly different threshold for MgB2.

Liu, Xiangdong; Panguluri, Raghava P.; Shoemaker, Daniel P.; Huang, Zhi-Feng; Nadgorny, Boris

2010-03-01

205

Double Percolation Transition in Superconductor-Ferromagnet Nanocomposites  

NASA Astrophysics Data System (ADS)

A double percolation transition is identified in a binary network composed of nanoparticles of MgB2 superconductor and CrO2 half-metallic ferromagnet. Anomalously high-resistance or insulating state, as compared to the conducting or superconducting states in single-component systems of either constituent, is observed between two distinct percolation thresholds. This double percolation effect, which is especially pronounced at liquid helium temperatures, is controlled by composite volume fraction and originates from the suppressed interface conduction and tunneling as well as a large geometric disparity between nanoparticles of different species. We investigate the scaling behavior near both percolation thresholds and determine the distinct critical exponents associated with two different types of transitions.

Liu, Xiangdong; Panguluri, Raghava P.; Huang, Zhi-Feng; Nadgorny, Boris

2010-01-01

206

Gate control of percolative conduction in strongly correlated manganite films.  

PubMed

Gate control of percolative conduction in a phase-separated manganite system is demonstrated in a field-effect transistor geometry, resulting in ambipolar switching from a metallic state to an insulating state. PMID:24481897

Hatano, Takafumi; Sheng, Zhigao; Nakamura, Masao; Nakano, Masaki; Kawasaki, Masashi; Iwasa, Yoshihiro; Tokura, Yoshinori

2014-05-01

207

Structure of Mandelbrot's Percolation Process and Other Random Cantor Sets.  

National Technical Information Service (NTIS)

The paper considers generalizations of Mandelbrot's percolation process. For the process called the random Sierpinski carpet, it shows that it passes through several different phases as its parameter increases from zero to one. The final section treats th...

F. M. Dekking R. W. J. Meester

1989-01-01

208

Percolation of polyatomic species on a simple cubic lattice  

NASA Astrophysics Data System (ADS)

In the present paper, the site-percolation problem corresponding to linear k-mers (containing k identical units, each one occupying a lattice site) on a simple cubic lattice has been studied. The k-mers were irreversibly and isotropically deposited into the lattice. Then, the percolation threshold and critical exponents were obtained by numerical simulations and finite-size scaling theory. The results, obtained for k ranging from 1 to 100, revealed that (i) the percolation threshold exhibits a decreasing function when it is plotted as a function of the k-mer size; and (ii) the phase transition occurring in the system belongs to the standard 3D percolation universality class regardless of the value of k considered.

Garcia, G. D.; Sanchez-Varretti, F. O.; Centres, P. M.; Ramirez-Pastor, A. J.

2013-09-01

209

Chemical percolation model for coal devolatilization: Milestone report.  

National Technical Information Service (NTIS)

The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated coal based on the chemical structure of the parent coal. This document provides complete details of the development of the CPD model. Percolati...

T. H. Fletcher A. R. Kerstein R. J. Pugmire M. Solum D. M. Grant

1992-01-01

210

Recycle Used Oil on America Recycles Day  

NSDL National Science Digital Library

Motor oil doesn't wear out--it just gets dirty. Students and the general public may not know that used oil can be reused or recycled. The fact is, used oil can be re-fined, blended with additives, and used again. When you consider that 1.4 billion gallons

White, Boyd W.

2000-11-01

211

Factors influencing breath ammonia determination.  

PubMed

Amongst volatile compounds (VCs) present in exhaled breath, ammonia has held great promise and yet it has confounded researchers due to its inherent reactivity. Herein we have evaluated various factors in both breath instrumentation and the breath collection process in an effort to reduce variability. We found that the temperature of breath sampler and breath sensor, mouth rinse pH, and mode of breathing to be important factors. The influence of the rinses is heavily dependent upon the pH of the rinse. The basic rinse (pH 8.0) caused a mean increase of the ammonia concentration by 410 ± 221 ppb. The neutral rinse (pH 7.0), slightly acidic rinse (pH 5.8), and acidic rinse (pH 2.5) caused a mean decrease of the ammonia concentration by 498 ± 355 ppb, 527 ± 198 ppb, and 596 ± 385 ppb, respectively. Mode of breathing (mouth-open versus mouth-closed) demonstrated itself to have a large impact on the rate of recovery of breath ammonia after a water rinse. Within 30 min, breath ammonia returned to 98 ± 16% that of the baseline with mouth open breathing, while mouth closed breathing allowed breath ammonia to return to 53 ± 14% of baseline. These results contribute to a growing body of literature that will improve reproducibly in ammonia and other VCs. PMID:23774041

Solga, Steven F; Mudalel, Matthew; Spacek, Lisa A; Lewicki, Rafal; Tittel, Frank; Loccioni, Claudio; Russo, Adolfo; Risby, Terence H

2013-09-01

212

Ammonia Ice Clouds on Jupiter  

NASA Technical Reports Server (NTRS)

The top cloud layer on Jupiter is thought to consist of ammonia ice, but most of that ammonia 'hides' from spectrometers. It does not absorb light in the same way ammonia does. To many scientists, this implies that ammonia churned up from lower layers of the atmosphere 'ages' in some way after it condenses, possibly by being covered with a photochemically generated hydrocarbon mixture. The New Horizons Linear Etalon Imaging Spectral Array (LEISA), the half of the Ralph instrument that is able to 'see' in infrared wavelengths that are absorbed by ammonia ice, spotted these clouds and watched them evolve over five Jupiter days (about 40 Earth hours). In these images, spectroscopically identified fresh ammonia clouds are shown in bright blue. The largest cloud appeared as a localized source on day 1, intensified and broadened on day 2, became more diffuse on days 3 and 4, and disappeared on day 5. The diffusion seemed to follow the movement of a dark spot along the boundary of the oval region. Because the source of this ammonia lies deeper than the cloud, images like these can tell scientists much about the dynamics and heat conduction in Jupiter's lower atmosphere.

2007-01-01

213

Water Percolation Governs Polymorphic Transitions and Conductivity of DNA  

NASA Astrophysics Data System (ADS)

We report on the first computer simulation studies of the percolation transition of water at the surface of the DNA double helix. With increased hydration, the ensemble of small clusters merges into a spanning water network via a quasi-two-dimensional percolation transition. This transition occurs strikingly close to the hydration level where the B form of DNA becomes stable in experiment. Formation of spanning water networks results in sigmoidlike acceleration of long-range ion transport in good agreement with experiment.

Brovchenko, Ivan; Krukau, Aliaksei; Oleinikova, Alla; Mazur, Alexey K.

2006-09-01

214

Percolation critical exponents in scale-free networks  

Microsoft Academic Search

We study the behavior of scale-free networks, having connectivity distribution P(k)~k-lambda, close to the percolation threshold. We show that for networks with 3percolation in infinite dimensions. Networks with 2

Reuven Cohen; Daniel Ben-Avraham; Shlomo Havlin

2002-01-01

215

Sol-gel-derived percolative copper film  

SciTech Connect

Cu-SiO{sub 2} films were prepared by the sol-gel method. Two-dimensional fractal copper films were formed after the films were thermally treated in reducing atmosphere. dc resistances of the films decrease 12 orders of magnitude as the content of copper increases from 70 to 80 mol%. During the resistance measurement under argon atmosphere, samples showed a sharp increase or decrease of resistance at a transition temperature which is ascribed to the oxidation of Cu into CuO. The oxidation was also observed in the in situ high temperature X-ray diffraction under vacuum condition. The evolution of the morphology of the films was studied by scanning electron microscopy. As the content of copper increases, the forms of copper particles change from discrete to aggregate then to interconnecting. The coverage coefficients of the copper range from 23 to 55% and the fractal dimensions range from 1.65 to 1.77. The percolation thresholds for the coverage coefficient and the fractal dimension are about 33% and 1.71, respectively, which corresponds to the sample containing 72.5 mol% of Cu.

Szu Sungping [Department of Physics, National Chung-Hsing University, Taichung 402, Taiwan (China)], E-mail: spszu@phys.nchu.edu.tw; Cheng, C.-L. [Department of Physics, National Chung-Hsing University, Taichung 402, Taiwan (China)

2008-10-02

216

Intra-Cluster Percolation of Calcium Signals  

PubMed Central

Calcium signals are involved in a large variety of physiological processes. Their versatility relies on the diversity of spatio-temporal behaviors that the calcium concentration can display. Calcium entry through inositol 1,4,5-trisphosphate (IP) receptors (IPR's) is a key component that participates in both local signals such as “puffs” and in global waves. IPR's are usually organized in clusters on the membrane of the endoplasmic reticulum and their spatial distribution has important effects on the resulting signal. Recent high resolution observations [1] of Ca puffs offer a window to study intra-cluster organization. The experiments give the distribution of the number of IPR's that open during each puff without much processing. Here we present a simple model with which we interpret the experimental distribution in terms of two stochastic processes: IP binding and unbinding and Ca-mediated inter-channel coupling. Depending on the parameters of the system, the distribution may be dominated by one or the other process. The transition between both extreme cases is similar to a percolation process. We show how, from an analysis of the experimental distribution, information can be obtained on the relative weight of the two processes. The largest distance over which Ca-mediated coupling acts and the density of IP-bound IPR's of the cluster can also be estimated. The approach allows us to infer properties of the interactions among the channels of the cluster from statistical information on their emergent collective behavior.

Solovey, Guillermo; Dawson, Silvina Ponce

2010-01-01

217

AQUEOUS AMMONIA EQUILIBRIUM - TABULATION OF PERCENT UN-IONIZED AMMONIA  

EPA Science Inventory

The percent of un-ionized ammonia as a function of pH and temperature in aqueous ammonia solutions of zero salinity is presented in tabular form over the following ranges: temperature 0.0 to 40.0 C in increments of 0.2 degree, and pH 5.00 to 12.00 in increments of 0.01 pH unit....

218

Ammonia as efficient fuel for SOFC  

Microsoft Academic Search

Ammonia is a possible candidate as the fuel for SOFCs. In this work, the influence on the performance of a tubular SOFC running on ammonia is studied. Analysis of open circuit voltages (OCVs) on the cell indicated the oxidation of ammonia within a SOFC is a two-stage process: decomposition of the inlet ammonia into nitrogen and hydrogen, followed by oxidation

A. Fuerte; R. X. Valenzuela; M. J. Escudero; L. Daza

2009-01-01

219

ENGINEERING DESIGN CONFIGURATIONS FOR BIOLOGICAL AMMONIA REMOVAL  

EPA Science Inventory

Many regions in the United States have excessive levels of nutrients including ammonia in their source waters. For example, farming and agricultural sources of ammonia in the Midwest contribute to relatively high levels of ammonia in many ground waters. Although ammonia in water ...

220

Dragnet: Nonprofit Computer Recyclers  

NSDL National Science Digital Library

If you have ever wondered what happens to obsolete computers, check out these current awareness Websites. The disposal of computers is classified as hazardous waste, which has become an environmental concern as the number of obsolete computers rises. In fact, the Wisconsin Department of Natural Resources and the State of Massachusetts have banned computer equipment from landfills. Dragnet: Nonprofit Computer Recyclers is an EPA-licensed computer recycling organization that reuses all acceptable components and systems or recycles damaged or unusable components. Rebuilt computer systems are given to "persons with disabilities and persons living in disadvantaged situations."

221

Compatibility testing with anhydrous ammonia  

NASA Technical Reports Server (NTRS)

Anhydrous ammonia has been proposed as the working fluid for a number of two-phase thermal control systems to be used in future space applications, including the Space Station Freedom and the Earth Observing Station (EOS). The compatibility of ammonia with the components in these systems is a major concern due to the corrosive nature of the fluid. Compatibility of ammonia with stainless steel and some aluminum alloys is well documented; however, data on other materials potentially suitable for aerospace use is less common. This paper documents the compatibility testing of nine materials with both gaseous and liquid ammonia. The test procedures are presented along with the resulting measurement data. Tensile strength was the only mechanical property tested that indicated a significant material incompatibility.

Benner, Steve M.; Schweickart, Russell B.

1992-01-01

222

Observation of interstellar ammonia ice  

NASA Technical Reports Server (NTRS)

An absorption band probably due to solid ammonia on interstellar grains has been detected in the infrared spectrum at 2.97 microns of the Becklin-Neugebauer object and probably in NGC 2264-IR. An ammonia-water amorphous ice mixture can explain the structure of the new band and of the 3.07 microns interstellar absorption. Laboratory data suggest that a long wavelength wind extending to 3.5 microns in interstellar dust spectra may be absorption by NH3-H2O complexes in the ices. In the molecular cloud obscuring the BN object, about 20 times as much NH3 is frozen in grains as exists in the gas phase, suggesting the gas-grain interactions may be important in the ammonia chemistry of molecular clouds. Arguments are given that interstellar features at 6.0 and 6.8 microns are also ammonia-related absorptions.

Knacke, R. F.; Mccorkle, S.; Puetter, R. C.; Erickson, E. F.; Kraetschmer, W.

1982-01-01

223

The Totem Pole Recycled.  

ERIC Educational Resources Information Center

Presents an activity that integrates science, environmental education, art, and social studies. Students identify and research an endangered species and construct a totem pole depicting the species using a recyclable material. (MDH)

Sewall, Susan Breyer

1991-01-01

224

A Practical Recycling Project . . .  

ERIC Educational Resources Information Center

Descirbes a school district's recycling program of aluminum lunch trays that are collected after their use. The trays are used as scrap metal in industrial education workshop and used for sand castings. (PS)

Durant, Raymond H.; Mikuska, James M.

1973-01-01

225

Reduce, Reuse, Recycle  

NSDL National Science Digital Library

In this media-rich lesson featuring LOOP SCOOPS videos, students consider how the concept of needs vs. wants can help them think about ways to protect Earth's natural resources by reducing, reusing, and recycling materials.

Foundation, Wgbh E.

2010-11-30

226

Making Recycled Paper  

NSDL National Science Digital Library

In this activity on page 11 of the PDF, learners follow simple steps to recycle old newspaper into new paper. Use this activity to introduce conservation as well as the chemistry of cellulose and how paper products are made.

Society, American C.

2011-01-01

227

Satellite Observations of Tropospheric Ammonia  

NASA Astrophysics Data System (ADS)

Global high-spectral resolution (0.06 cm-1) nadir measurements from TES-Aura enable the simultaneous retrieval of a number of tropospheric pollutants and trace gases in addition to the TES standard operationally retrieved products (e.g. carbon monoxide, ozone). Ammonia (NH3) is one of the additional species that can be retrieved in conjunction with the TES standard products, and is important for local, regional, and global tropospheric chemistry studies. Ammonia emissions contribute significantly to several well-known environmental problems, yet the magnitude and seasonal/spatial variability of the emissions are poorly constrained. In the atmosphere, an important fraction of fine particulate matter is composed of ammonium nitrate and ammonium sulfate. These particles are statistically associated with health impacts. When deposited to ecosystems in excess, nitrogen, including ammonia can cause nutrient imbalances, change in ecosystem species composition, eutrophication, algal blooms and hypoxia. Ammonia is also challenging to measure in-situ. Observations of surface concentrations are rare and are particularly sparse in North America. Satellite observations of ammonia are therefore highly desirable. We recently demonstrated that tropospheric ammonia is detectable in the TES spectra and presented some corresponding preliminary retrievals over a very limited range of conditions (Beer et al., 2008). Presented here are results that expand upon these initial TES ammonia retrievals in order to evaluate/validate the retrieval results utilizing in-situ surface observations (e.g. LADCO, CASTNet, EPA /NC State) and chemical models (e.g. GEOS-Chem and CMAQ). We also present retrievals over regions of interest that have the potential to help further understand air quality and the active nitrogen cycle. Beer, R., M. W. Shephard, S. S. Kulawik, S. A. Clough, A. Eldering, K. W. Bowman, S. P. Sander, B. M. Fisher, V. H. Payne, M. Luo, G. B. Osterman, and J. R. Worden, First satellite observations of lower tropospheric ammonia and methanol, Geophysical Res. Letters, 35, L09801, doi:10.1029/2008GL033642, 2008.

Shephard, M. W.; Luo, M.; Rinsland, C. P.; Cady-Pereira, K. E.; Beer, R.; Pinder, R. W.; Henze, D.; Payne, V. H.; Clough, S.; Rodgers, C. D.; Osterman, G. B.; Bowman, K. W.; Worden, H. M.

2008-12-01

228

Climate Kids: Recycle This!  

NSDL National Science Digital Library

The site features an online game in which participants keep recyclable items out of the trash by guiding them into proper bins. Accompanying the game is a list of three categories of items that can be recycled, along with the benefits of doing so. This lesson is part of the Climate Kids website, a NASA education resource featuring articles, videos, images and games focused on the science of climate change.

229

Recyclability Index for Automobiles  

Microsoft Academic Search

A rating system was developed to quantify the environmental impacts of light-duty motor vehicles at the end of their life-cycle based on recyclability, toxic material content and ultimate disposal. Each year, 10-11 million vehicles are retired from service in the United States. The vehicle material not recycled is called automotive shredder residue (ASR). About 4.5 to 5 million tons of

Alexander Tsuji; Yarrow Nelson; Andrew Kean; Samuel A. Vigil

2006-01-01

230

Estimation of the percolation thresholds in acyclovir hydrophilic matrix tablets.  

PubMed

The principles of percolation theory were applied to design controlled release matrix tablets containing acyclovir. This statistical theory studies disordered or chaotic systems where the components are randomly distributed in a lattice. The application of this theory to study the release and hydration rate of hydrophilic matrices allows to explain the changes in release and hydration kinetics of swellable matrix type controlled delivery systems. The objective of the present paper is to estimate the percolation threshold of HPMC K4M in matrices of acyclovir and to apply the obtained result to the design of hydrophilic matrices for the controlled delivery of this drug. Matrix tablets have been prepared using acyclovir as drug and HPMC K4M as matrix forming material, employing five different excipient/drug percentages. Dissolution studies were carried out using the paddle method. Water uptake measurements were performed using a modified Enslin apparatus. In order to estimate the percolation threshold, the behaviour of the kinetic parameters with respect to the excipient volumetric fraction at time zero plus initial porosity was studied. According to percolation theory, the critical points observed in dissolution and water uptake studies can be attributed to the excipient percolation threshold. This threshold was situated between between 20.76% and 26.41% v/v of excipient plus initial porosity. The knowledge of the percolation threshold of the components of the matrix formulations contributes to improve their design. First, reducing the time to market and second, increasing their robustness when they are prepared at Industrial scale, avoiding the formulation in the nearby of the percolation threshold. PMID:16876392

Fuertes, Inmaculada; Miranda, Antonia; Millán, Mónica; Caraballo, Isidoro

2006-11-01

231

Recycling of nonmetallics  

USGS Publications Warehouse

The first factor determining recyclability is the composition of the material itself. Metals, for example, can be reused with little or no loss in quality. Paper and rubber, by this criterion, are less recyclable. Each time paper is recycled, some cellulose fibers are broken. Shorter fibers can mean weaker paper of perceived lower quality and value. Vulcanizing is an irreversible chemical process that precludes recycling rubber in its original form. Both materials may be reused in other applications often of lower value than the original one. To be recyclable, the discarded material must have a collection infrastructure at the source of waste generation, at a central collection site, or at curbside. The recovered material must also have a market. If it is priced noncompetitively or no market exists, if it does not meet specifications, or if it requires special technology investments which cannot be recovered through future sales, the recovered material may be stockpiled or discarded rather than recycled. ?? 1996 International Association for Mathematical Geology.

Amey, E. B.; Kelly, T. D.

1996-01-01

232

Intracage ammonia levels in static and individually ventilated cages housing C57BL/6 mice on 4 bedding substrates.  

PubMed

The relationship among ammonia levels, cage-changing frequency, and bedding types is an important and potentially controversial topic in the laboratory animal science community. Some bedding options may not provide sufficient urine absorption and bacterial regulation to minimize ammonia production during the interval between cage changes. High intracage ammonia levels can cause subclinical degeneration and inflammation of nasal passages, rhinitis and olfactory epithelial necrosis in exposed mice. Here we sought to compare the effects of 4 commonly used bedding substrates (1/4-in. irradiated corncob, reclaimed wood pulp, aspen wood chips, and recycled newspaper) on ammonia generation when housing female C57BL/6 mice in static and individually ventilated caging. Intracage ammonia levels were measured daily for 1 wk (static cage experiment) or 2 wk (IVC experiment). The results of this study suggest that the corncob, aspen wood chip, and recycled newspaper beddings that we tested are suitable for once-weekly cage changing for static cages and for changing every 2 wk for IVC. However, ammonia levels were not controlled appropriately in cages containing reclaimed wood pulp bedding, and pathologic changes occurred within 1 wk in the nares of mice housed on this bedding in static cages. PMID:24602540

Ferrecchia, Christie E; Jensen, Kelly; Van Andel, Roger

2014-03-01

233

Dynamics of percolation phenomena in colloidal printing inks  

NASA Astrophysics Data System (ADS)

The conductivity of colloidal inks composed of poly(ethylene glycol) (PEG), 2-(4-tert-Butylphenyl)-5-(4-biphenylyl)- 1,3,4-oxadiazole (tPBD) or polystyrene-tPBD copolymerized colloids (PS-PBD) and carbon black (CB) were investigated to establish their percolation characteristics. The PS-PBD colloid supported inks (PEG/PS-PBD/CB) exhibited reduced percolation thresholds and enhanced conductivities above that of the individually carbon filled (PEG/CB) and small molecule blend (PEG/tPBD/CB) inks. Based on the DC conductivity analysis, the percolation threshold of the PEG/PS-PBD/CB composites was 3.6 vol%. The electrical resistivity of the PEG/PS-PBD/CB ink is lower than that of PEG/PBD/CB ink with the same CB content in the percolation region by 8 orders of magnitude. The percolation reduction was attributed to the heterogeneous dispersion of conductive filler aggregates "bridged" by PSPBD colloids. The aggregated dispersion of PS-PBD colloids in the ink matrix was characterized by photoluminescence spectroscopy (PL) which produced a red-shift at high concentrations, signaling the required proximity of PS-PBD colloids to form energy transfer complexes.

Daniele, Michael Angelo-Anthony; Foguth, Alexandra L.; Rungta, Parul; Bandera, Iurii; Tsyalkovskyy, Volodymyr; Foulger, Stephen H.

2010-02-01

234

An Experimental Approach to the Percolation of Sticky Nanotubes  

NASA Astrophysics Data System (ADS)

Percolation is a statistical concept that describes the formation of an infinite cluster of connected particles or pathways. Lowering the percolation threshold is a critical issue to achieve light and low-cost conductive composites made of an insulating matrix loaded with conductive particles. This has interest for applications where charge dissipation and electrical conductivity are sought in films, coatings, paints, or composite materials. One route to decreasing the loading required for percolation is to use rod-like particles. Theoretical predictions indicate that this may also be achieved by altering the interaction potential between the particles. Although percolation may not always respond monotonically to interactions, the use of adhesive rods can be expected to be an ideal combination. By using a system made of carbon nanotubes in an aqueous surfactant solution, we find that very small attraction can markedly lower the percolation threshold. The strength of this effect can thereby have direct technological interest and explain the large variability of experimental results in the literature dealing with the electrical behavior of composites loaded with conducting rods.

Vigolo, B.; Coulon, C.; Maugey, M.; Zakri, C.; Poulin, P.

2005-08-01

235

Invasion percolation through minimum-weight spanning trees  

NASA Astrophysics Data System (ADS)

Invasion percolation is often used to simulate capillary-dominated drainage and imbibition in pore networks. More than a decade ago it was observed that the part of a pore network that is involved in an invasion bond percolation is a minimum-weight spanning tree of the network, where the weights indicate resistances associated with the bonds. Thus, one can determine a minimum-weight spanning tree first and then run the invasion bond percolation on the minimum-weight spanning tree. The time complexities of the two steps are O(m?(m,n)) and O(n) , respectively, where m is the number of edges, n is the number of vertices, and ?(?,?) denotes the inverse Ackermann function. In this paper we (1) formulate the property of minimum-weight spanning trees that justifies the two-step approach to invasion bond percolation, (2) extend the two-step approach to invasion site percolation, and (3) further extend it to simulations of drainage (imbibition) that include trapping of the wetting (nonwetting) phase. In case of imbibition we also take snap-off into account. As a consequence, all these simulations can now be done in O(m?(m,n)) .

Glantz, Roland; Hilpert, Markus

2008-03-01

236

MEASUREMENT OF AMMONIA RELEASE FROM SALTSTONE  

SciTech Connect

SRNL was requested by WSRC Waste Solidification Engineering to characterize the release of ammonia from saltstone curing at 95 C by performing experimental testing. These tests were performed with an MCU-type Tank 50H salt simulant containing 0, 50, and 200 mg/L ammonia. The testing program showed that above saltstone made from the 200 mg/L ammonia simulant, the vapor space ammonia concentration was about 2.7 mg/L vapor at 95 C. An upper 95% confidence value for this concentration was found to be 3.9 mg/L. Testing also showed that ammonia was chemically generated from curing saltstone at 95 C; the amount of ammonia generated was estimated to be equivalent to 121 mg/L additional ammonia in the salt solution feed. Even with chemical generation, the ammonia release from saltstone was found to be lower than its release from salt solution only with 200 mg/L ammonia.

Zamecnik, J; Alex Cozzi, A

2009-01-15

237

Recycling of Reinforced Plastics  

NASA Astrophysics Data System (ADS)

This work has shown is that it is possible to recycle continuous and short fibre reinforced thermosetting resins while keeping almost the whole of the original material, both fibres and matrix, within the recyclate. By splitting, crushing hot or cold, and hot forming, it is possible to create a recyclable material, which we designate a Remat, which can then be used to remanufacture other shapes, examples of plates and tubes being demonstrated. Not only can remanufacturing be done, but it has been shown that over 50 % of the original mechanical properties, such as the E modulus, tensile strength, and interlaminar shear strength, can be retained. Four different forms of composite were investigated, a random mat Glass Fibre Reinforced Plastic (GFRP) bathroom component and boat hull, woven glass and carbon fibre cloth impregnated with an epoxy resin, and unidirectional carbon fibre pre-preg. One of the main factors found to affect composite recyclability was the type of resin matrix used in the composite. Thermoset resins tested were shown to have a temperature range around the Glass Transition Temperature (Tg) where they exhibit ductile behaviour, hence aiding reforming of the material. The high-grade carbon fibre prepreg was found to be less easy to recycle than the woven of random fibre laminates. One method of remanufacturing was by heating the Remat to above its glass transition temperature, bending it to shape, and then cooling it. However, unless precautions are taken, the geometric form may revert. This does not happen with the crushed material.

Adams, R. D.; Collins, Andrew; Cooper, Duncan; Wingfield-Digby, Mark; Watts-Farmer, Archibald; Laurence, Anna; Patel, Kayur; Stevens, Mark; Watkins, Rhodri

2014-02-01

238

Critical exponents of protonic percolation in maize seeds  

NASA Astrophysics Data System (ADS)

The hydration-dependent dc conductivity of the two main components (embryo and endosperm) of a viable maize seed has been measured by a dielectric-gravimetric technique. The protonic conductivity, plotted as a function of the sample water content, displays a percolative behavior characterized by a threshold and by a critical exponent in agreement with theory for a two-dimensional process. This percolative water-assisted process reflects the presence of an extended network of water molecules adsorbed on the surface of proteins and/or membranes inside intact cells. Moreover, the percolation threshold is found close to the onset of the biological function of these tissues, where the early enzymatic activity leads to the onset of metabolism, a prerequisite to the commencement of germination.

Bruni, F.; Careri, G.; Leopold, A. C.

1989-09-01

239

Incomplete and noisy network data as a percolation process  

PubMed Central

We discuss the ramifications of noisy and incomplete observations of network data on the existence of a giant connected component (GCC). The existence of a GCC in a random graph can be described in terms of a percolation process, and building on general results for classes of random graphs with specified degree distributions we derive percolation thresholds above which GCCs exist. We show that sampling and noise can have a profound effect on the perceived existence of a GCC and find that both processes can destroy it. We also show that the absence of a GCC puts a theoretical upper bound on the false-positive rate and relate our percolation analysis to experimental protein–protein interaction data.

Stumpf, Michael P. H.; Wiuf, Carsten

2010-01-01

240

Connecting Core Percolation and Controllability of Complex Networks  

PubMed Central

Core percolation is a fundamental structural transition in complex networks related to a wide range of important problems. Recent advances have provided us an analytical framework of core percolation in uncorrelated random networks with arbitrary degree distributions. Here we apply the tools in analysis of network controllability. We confirm analytically that the emergence of the bifurcation in control coincides with the formation of the core and the structure of the core determines the control mode of the network. We also derive the analytical expression related to the controllability robustness by extending the deduction in core percolation. These findings help us better understand the interesting interplay between the structural and dynamical properties of complex networks.

Jia, Tao; Posfai, Marton

2014-01-01

241

Cluster size distribution in percolation theory and fractal Cantor dust  

NASA Astrophysics Data System (ADS)

Results of numerical simulation of cluster size distribution in the site percolation problem are presented. These results disagree with the theoretical data obtained on the basis of the standard drop model of finite cluster structure, in particular, they give a different value of exponent ? (lnns˜-s?). Therefore, a more precise fractal model for describing the structure of clusters in a percolation system is proposed. The consideration is based on the solution of a kinetic equation for the number of finite clusters. In the framework of the proposed approach (fractal model together with kinetic equation), a correct value of exponent ? is obtained and an explanation is given to the dependence of this exponent on the fraction of occupied sites p, which was revealed by numerical simulations. Additionally, a relation is established between the characteristics of cluster size distribution and fractal dimension of the Cantor dust constructed on the percolation cluster.

Grinchuk, Pavel

2007-04-01

242

Connecting core percolation and controllability of complex networks.  

PubMed

Core percolation is a fundamental structural transition in complex networks related to a wide range of important problems. Recent advances have provided us an analytical framework of core percolation in uncorrelated random networks with arbitrary degree distributions. Here we apply the tools in analysis of network controllability. We confirm analytically that the emergence of the bifurcation in control coincides with the formation of the core and the structure of the core determines the control mode of the network. We also derive the analytical expression related to the controllability robustness by extending the deduction in core percolation. These findings help us better understand the interesting interplay between the structural and dynamical properties of complex networks. PMID:24946797

Jia, Tao; Pósfai, Márton

2014-01-01

243

Scaling behavior of explosive percolation on the square lattice  

NASA Astrophysics Data System (ADS)

Clusters generated by the product-rule growth model of Achlioptas, D’Souza, and Spencer on a two-dimensional square lattice are shown to obey qualitatively different scaling behavior than standard (random growth) percolation. The threshold with unrestricted bond placement (allowing loops) is found precisely using several different criteria based on both moments and wrapping probabilities, yielding pc=0.526565±0.000005 , consistent with the recent result of Radicchi and Fortunato. The correlation-length exponent ? is found to be close to 1. The qualitative difference from regular percolation is shown dramatically in the behavior of the percolation probability P? (size of largest cluster), of the susceptibility, and of the second moment of finite clusters, where discontinuities appear at the threshold. The critical cluster-size distribution does not follow a consistent power law for the range of system sizes we study (L?8192) but may approach a power law with ?>2 for larger L .

Ziff, Robert M.

2010-11-01

244

Fast and accurate database searches with MS-GF+Percolator.  

PubMed

One can interpret fragmentation spectra stemming from peptides in mass-spectrometry-based proteomics experiments using so-called database search engines. Frequently, one also runs post-processors such as Percolator to assess the confidence, infer unique peptides, and increase the number of identifications. A recent search engine, MS-GF+, has shown promising results, due to a new and efficient scoring algorithm. However, MS-GF+ provides few statistical estimates about the peptide-spectrum matches, hence limiting the biological interpretation. Here, we enabled Percolator processing for MS-GF+ output and observed an increased number of identified peptides for a wide variety of data sets. In addition, Percolator directly reports p values and false discovery rate estimates, such as q values and posterior error probabilities, for peptide-spectrum matches, peptides, and proteins, functions that are useful for the whole proteomics community. PMID:24344789

Granholm, Viktor; Kim, Sangtae; Navarro, José C F; Sjölund, Erik; Smith, Richard D; Käll, Lukas

2014-02-01

245

Mesoscale modeling of electrical percolation in fiber-filled systems.  

PubMed

The research described in this paper primarily involves mesoscale simulations: dissipative particle dynamics (DPD) of packed assemblies of oriented fibers suspended in a viscous medium. Computer simulations have been performed in order to explore how the aspect ratio and degree of fiber alignment affect the critical volume fraction (percolation threshold) required to achieve electrical conductivity. The fiber network impedance was assessed using Monte Carlo simulations after establishing the structural arrangement with DPD. The predictions are compared with the predictions of classical percolation theory and found to be in close agreement. The approach is thus validated and can be extended to systems that cannot be tackled analytically; in particular, the work is motivated by long-standing interest in materials which display a complex percolation behavior. PMID:16223321

Rahatekar, Sameer S; Hamm, Marc; Shaffer, Milo S P; Elliott, James A

2005-10-01

246

Continuum percolation threshold for interpenetrating squares and cubes.  

PubMed

Monte Carlo simulations are performed to determine the critical percolation threshold for interpenetrating square objects in two dimensions and cubic objects in three dimensions. Simulations are performed for two cases: (i) objects whose edges are aligned parallel to one another and (ii) randomly oriented objects. For squares whose edges are aligned, the critical area fraction at the percolation threshold phi(c)=0.6666+/-0.0004, while for randomly oriented squares phi(c)=0.6254+/-0.0002, 6% smaller. For cubes whose edges are aligned, the critical volume fraction at the percolation threshold phi(c)=0.2773+/-0.0002, while for randomly oriented cubes phi(c)=0.2168+/-0.0002, 22% smaller. PMID:12443288

Baker, Don R; Paul, Gerald; Sreenivasan, Sameet; Stanley, H Eugene

2002-10-01

247

Variable percolation threshold of composites with fiber fillers under compression  

NASA Astrophysics Data System (ADS)

The piezoresistant effect in conducting fiber-filled composites has been studied by a continuum percolation model. Simulation was performed by a Monte Carlo method that took into account both the deformation-induced fiber bending and rotation. The percolation threshold was found to rise with the compression strain, which explains the observed positive piezoresistive coefficients in such composites. The simulations unveiled the effect of the microstructure evolution during deformation. The fibers are found to align perpendicularly to the compression direction. As the fiber is bended, the effective length in making a conductive network is shortened. Both effects contribute to a larger percolation threshold and imply a positive piezoresistive coefficient according the universal power law.

Lin, Chuan; Wang, Hongtao; Yang, Wei

2010-07-01

248

TES Observations of Tropospheric Ammonia  

NASA Astrophysics Data System (ADS)

Ammonia emissions contribute significantly to several well-known environmental problems, yet the knowledge of the magnitude and seasonal/spatial variability of the emissions is severely limited. In the atmosphere, a substantial fraction of fine particulate matter is composed of ammonium nitrate and ammonium sulfate. These particles are statistically associated with health impacts. When deposited to ecosystems in excess, reactive nitrogen, including ammonia, can cause nutrient imbalances, changes in ecosystem species composition, algal blooms and hypoxia. The greatest uncertainty in atmospheric transport of reactive nitrogen is in the rates of ammonia emission from all sources, at all scales. In-situ ammonia measurements are challenging and not available in many regions. Limiting factors in improving the emission inventory are infrequent and sparse in-situ observations and the reliance of previous inversion methods using a limited number of available condensed-phase measurements. Satellite observations of ammonia are therefore highly desirable. Presented are validations of Tropospheric Emission Spectrometer (TES) retrievals utilizing long term in-situ surface observations (e.g. EPA /NC State) and chemical models (e.g. GEOS-Chem and CMAQ) over a much broader range of conditions. We also discuss the estimated impact of TES retrievals on quantifying emission sources through inverse modeling.

Shephard, M. W.; Luo, M.; Cady-Pereira, K. E.; Pinder, R. W.; Henze, D. K.; Walker, J. T.; Rinsland, C. P.; Beer, R.; Payne, V.

2009-12-01

249

Scrap tire recycling  

SciTech Connect

As the automobile tire technology has grown and met the need for safer and more durable tires, stronger reinforcement and more chemically resistant rubber compounds have made recycling tires more difficult. In an effort to resolve this problem, techniques and equipment were developed to grind tires into small pieces, and new markets were sought to utilize the crumb rubber product streams from ground tires. Industrial combustion processes were modified to accept scrap tires as fuel. These efforts have been beneficial, steadily increasing the percentage of scrap tires recycled to about 10% in 1985, and reaching 72% in 1995. By the end of 1997, fully 100% of tires generated in the U.S. are expected to be recycled.

Lula, J.W.; Bohnert, G.W.

1997-03-01

250

Test of scaling exponents for percolation-cluster perimeters  

NASA Astrophysics Data System (ADS)

The formula for the fractal dimensionality of the perimeter (hull) of a percolation cluster, d'f=1+1/?, proposed recently by Sapoval, Rosso, and Gouyet, is shown to imply for the perimeter scaling exponents ?'=1+2?/(1+?), ?'=1/(1+?), and ?'=2. Monte Carlo simulations of very large perimeter-generating walks yield ?'=2.143+/-0.002 and d'f=1.751+/-0.002, consistent with these predictions (on the assumption that ?=(4/3)). The walks are also used to determine pc=0.5927 5+/-0.0000 3 for site percolation on a square lattice.

Ziff, Robert M.

1986-02-01

251

Dynamics of percolation phenomena in colloidal printing inks  

Microsoft Academic Search

The conductivity of colloidal inks composed of poly(ethylene glycol) (PEG), 2-(4-tert-Butylphenyl)-5-(4-biphenylyl)- 1,3,4-oxadiazole (tPBD) or polystyrene-tPBD copolymerized colloids (PS-PBD) and carbon black (CB) were investigated to establish their percolation characteristics. The PS-PBD colloid supported inks (PEG\\/PS-PBD\\/CB) exhibited reduced percolation thresholds and enhanced conductivities above that of the individually carbon filled (PEG\\/CB) and small molecule blend (PEG\\/tPBD\\/CB) inks. Based on the DC

Michael Angelo-Anthony Daniele; Alexandra L. Foguth; Parul Rungta; Iurii Bandera; Volodymyr Tsyalkovskyy; Stephen H. Foulger

2010-01-01

252

Remnant percolative disorder in highly-cured networks  

SciTech Connect

The authors have previously reported viscoelastic measurements demonstrating that fully-cured networks and critical gels exhibit similar relaxation spectra, implying that fully-cured networks are somewhat ill- connected. Here, they present restricted valence percolation simulations of networks well beyond the percolation transition that explicitly display remnant disorder over length scales less than the correlation length of the network. They conclude that the topology of highly-cured networks is not well described by a regular three- dimensional tennis net but is ill-connected over length scales that correspond to relaxation modes of practical interest.

Adolf, D.; Hance, B.; Martin, J.E. (Sandia National Labs., Albuquerque, NM (United States))

1993-05-24

253

Distribution of blocking temperatures in spin glass transition: Percolation model  

NASA Astrophysics Data System (ADS)

We calculate the distribution of blocking temperatures f( T) in amorphous spin glass alloy (Fe 0.64Mn 0.36) 75P 16B 6Al 3 by comparing Mookerjee and Chowdhury's percolation model (based on Mydosh's qualitative picture) with experimental data. The qualitative features are in good agreement with f( T) for canonical spin glass CuMn (0.7 at %) and insulating spin glass CoO·Al 2O 3·SiO 2 (14.3 at % Co) obtained by Van Duyneveldt and Mulder. The sharp peak in f( T) near Tg is shown to be the manifestation of cooperative effect in the percolation process.

Chowdhury, D.; Mookerjee, A.

1984-05-01

254

Percolation models for boiling and bubble growth in porous media  

SciTech Connect

We analyze the liquid-to-vapor phase change in single-component fluids in porous media at low superheats. Conditions typical to steam injection in porous media are taken. We examine nucleation, phase equilibria and their stability, and the growth of vapor bubbles. Effects of pore structure are emphasized. It is shown that at low supersaturations, bubble growth can be described as a percolation process. In the absence of spatial gradients, macroscopic flow properties are calculated in terms of nucleation parameters. A modification of gradient percolation is also proposed in the case of spatial temperature gradients, when solid conduction predominates. 22 refs., 10 figs., 1 tab.

Yortsos, Y.C.

1991-05-01

255

The Ammonia Dimer Revisited  

NASA Astrophysics Data System (ADS)

The conclusion from microwave spectra by Nelson, Fraser, and Klemperer that the ammonia dimer has a nearly cyclic structure led to much debate about the issue of whether (NH_3)_2 is hydrogen bonded. This structure was surprising because most {ab initio} calculations led to a classical, nearly linear, hydrogen-bonded structure. An obvious explanation of the discrepancy between the outcome of these calculations and the microwave data which led Nelson {et al.} to their ``surprising structure'' might be the effect of vibrational averaging: the electronic structure calculations focus on finding the minimum of the intermolecular potential, the experiment gives a vibrationally averaged structure. Isotope substitution studies seemed to indicate, however, that the complex is nearly rigid. Additional data became available from high-resolution molecular beam far-infrared spectroscopy in the Saykally group. These spectra, displaying large tunneling splittings, indicate that the complex is very floppy. The seemingly contradictory experimental data were explained when it became possible to calculate the vibration-rotation-tunneling (VRT) states of the complex on a six-dimensional intermolecular potential surface. The potential used was a simple model potential, with parameters fitted to the far-infrared data. Now, for the first time, a six-dimensional potential was computed by high level {ab initio} methods and this potential will be used in calculations of the VRT states of (NH_3)_2 and (ND_3)_2. So, we will finally be able to answer the question whether the conclusions from the model calculations are indeed a valid explanation of the experimental data. D. Nelson, G. T. Fraser, and W. Klemperer J. Chem. Phys. 83 6201 (1985) J. G. Loeser, C. A. Schmuttenmaer, R. C. Cohen, M. J. Elrod, D. W. Steyert, R. J. Saykally, R. E. Bumgarner, and G. A. Blake J. Chem. Phys. 97 4727 (1992) E. H. T. Olthof, A. van der Avoird, and P. E. S. Wormer J. Chem. Phys. 101 8430 (1994) E. H. T. Olthof, A. van der Avoird, P. E. S. Wormer, J. G. Loeser, and R. J. Saykally J. Chem. Phys. 101 8443 (1994)

Dawes, Richard; Van Der Avoird, Ad

2012-06-01

256

Recycled Aluminum Ornaments  

NSDL National Science Digital Library

This lesson plan from ATEEC will explain the principles of recycling. The activity would be most appropriate for technology studies or high school science classes. In all, it would require 2-5 hours of class time to complete. The purpose of the lesson is to demonstrate how aluminum is recycled. This laboratory activity does require some special equipment including a heat source capable of melting aluminum and an outdoor work area. Extension activities are also provided. The lesson plan is available for download as a PDF; users must create a free, quick login with ATEEC to access the materials.

Wishart, Ray

2013-06-14

257

New Computer Programs Using Diurnal Temperature Time Series to Determine Streambed Percolation Velocities  

NASA Astrophysics Data System (ADS)

Streambed percolation is one of the most important routes for groundwater recharge. Among many methods, using diurnal temperature in the streambed to determine percolation velocity is one the most frequently used methods. Several numerical codes, VS2DH, SUTRA, and TOUGH2, have been developed primarily for 2D or 3D heat transport simulation and also for use in streambed percolation velocity calculation, but, with great complexity. This research simplifies percolation velocity calculation by developing new computer codes that solve the 1D heat transfer equation. Using diurnal temperature data, percolation velocity can be determined easily to each day of the monitoring period. More percolation velocity data will enable more understanding for the river/groundwater interaction. This work also conducts a field test for studying streambed percolation in the Choshui stream, Central Taiwan. The data show the average percolation velocity at approximately 6.8×10-6 m/s.

Chen, W.; Chen, J.; Lu, W.; Huang, C.

2012-12-01

258

Porous silicon ammonia gas sensor  

NASA Astrophysics Data System (ADS)

A planar optical waveguide is manufactured by the functionnalisation of oxidised mesoporous silicon with Bromothymol Blue to achieve a sensitive ammonia sensor suitable for low gas concentrations. The propagated light intensity is measured at the output of the waveguide. The sensitivity at low concentrations and the short time of reaction of the sensor are enhanced by a confinement effect of the gas molecules inside the pores. The dependence of the output signal with gas concentration is demonstrated. When the ammonia flow is stopped, the reversibility of the initial characteristics of the propagated light is naturally obtained with the disappearance of the gas molecules.

Chaillou, A.; Charrier, J.; Lorrain, N.; Sarret, M.; Haji, L.

2006-03-01

259

Catalytic Organometallic Reactions of Ammonia  

PubMed Central

Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen-containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross-coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity.

Klinkenberg, Jessica L.

2012-01-01

260

Colorimetric Analysis of Ammonia in Water.  

National Technical Information Service (NTIS)

An accurate, reliable method of determing concentration of ammonia in water solution was developed using colorimetric techniques. The procedure involves formation of a colored complex of ammonia with 2,5-dimethoxyoxolane and (E)-p-dimethylamino-cinnamalde...

F. W. Carson R. L. Gross

1977-01-01

261

Zeolite Ammonia Removal from Catfish Pond Waters,  

National Technical Information Service (NTIS)

The research focused on developing a zeolite filtration system which will prevent toxic ammonia build-up in catfish ponds. Zeolites are ion exchangers and some natural species are capable of selectively removing ammonia from various types of water systems...

W. R. Reynolds C. W. Williford

1987-01-01

262

Recycling Decisions and Green Design.  

ERIC Educational Resources Information Center

Explores the facts and perceptions regarding recycling, what can be done to make products more environmentally compatible, and how to think about recycling decisions in a more helpful way. (Contains 39 references.) (MDH)

Lave, Lester B.; And Others

1994-01-01

263

Recycling Opportunities for Neighbourhoods and Communities.  

National Technical Information Service (NTIS)

This paper discusses recycling paper, glass, plastics, and metals. It presents a community technology approach to recycling, and reviews present efforts in repair and renovation, reuse, and recycling. A final chapter on the appropriateness of recycling te...

C. Thomas

1981-01-01

264

Ammonia regeneration for a combined lime\\/ammonia spray dryer for SOâ control. Final report  

Microsoft Academic Search

A research project designed to study the feasibility of ammonia regeneration for a combined lime\\/ammonia FGD process was conducted at the University of Cincinnati. The major objective for this project was to regenerate ammonia from a combined ammonia\\/calcium hydroxide spray dryer FGD byproduct for reuse which would reduce the operating cost of this FGD process. This final report covers the

Xinjian

1992-01-01

265

Ammonia regeneration for a combined lime\\/ammonia spray dryer for SO[sub 2] control  

Microsoft Academic Search

A research project designed to study the feasibility of ammonia regeneration for a combined lime\\/ammonia FGD process was conducted at the University of Cincinnati. The major objective for this project was to regenerate ammonia from a combined ammonia\\/calcium hydroxide spray dryer FGD byproduct for reuse which would reduce the operating cost of this FGD process. This final report covers the

Xinjian

1992-01-01

266

Electrooxidation of ammonia in waste water  

Microsoft Academic Search

A study was undertaken of the electro-oxidation of ammonia as a possible new method of ammonia removal during waste-water treatment. Reaction rates were measured in the concentration range of 1.2×10-4 M to 1×10-2 M ammonia and at pH values of 5–13. The influence of the polarization rate (0.05–0.5 V min-1) and the ammonia concentrations on the oxidation peak current were

L. Marin?i?; F. B. Leitz

1978-01-01

267

The electrical conductivity of binary disordered systems, percolation clusters, fractals and related models  

Microsoft Academic Search

We review theoretical and experimental studies of the AC dielectric response of inhomogeneous materials, modelled as bond percolation networks, with a binary (conductor-dielectric) distribution of bond conductances. We first summarize the key results of percolation theory, concerning mostly geometrical and static (DC) transport properties, with emphasis on the scaling properties of the critical region around the percolation threshold. The frequency-dependent

J. P. Clerc; G. Giraud; J. M. Laugier; J. M. Luck

1990-01-01

268

Recycle Your Own Paper!  

NSDL National Science Digital Library

In this activity (page 2 of PDF), learners will prepare sheets of homemade recycled paper from several different source pulps. Once dry, each sample will be drawn on with a marker to test how far ink spreads in the fibers of the different kinds of papers. Relates to the linked video, DragonflyTV GPS: Garbology.

Twin Cities Public Television, Inc.

2007-01-01

269

Computer Recycling Farm USA  

USGS Multimedia Gallery

USGS conducted a study of plastic pollution at this rural US site in the Midwest.  The recycler was receiving computers from companies at a rate which greatly exceeded the capacity of the operation.  Approximately 50,000 computers remained outdoors on 15 acres for nearly a decade.  The site has sinc...

2010-08-13

270

Recycle of Waste Paper.  

National Technical Information Service (NTIS)

One of the Oak Ridge Y-12 Plant's long range goals is to reduce the amount of waste from the plant. The large amount of waste paper generated by the plant is currently buried in the state permitted landfill. Methods of recycling cardboard and paper which ...

G. D. Hackett G. E. Harris

1988-01-01

271

Recycled Insect Models  

ERIC Educational Resources Information Center

This article presents an engaging activity in which high school students use a dichotomous key to guide the creation and classification of model insects from recycled plastic lids and containers. Besides teaching the use of a dichotomous key and the effect of evolutionary descent upon groupings of organisms, this activity focuses on an…

Rule, Audrey C.; Meyer, Mary Ann

2007-01-01

272

Recycling Study Guide.  

ERIC Educational Resources Information Center

This study guide was designed to help teachers and students understand the problems surrounding solid wastes. It includes an overview of solid waste and recycling, a glossary, suggested activities and a list of resource publications, audiovisual materials and organizations. There are 19 activity suggestions included in this guide designed for use…

Hallowell, Anne; And Others

273

Helium-Recycling Plant  

NASA Technical Reports Server (NTRS)

Proposed system recovers and stores helium gas for reuse. Maintains helium at 99.99-percent purity, preventing water vapor from atmosphere or lubricating oil from pumps from contaminating gas. System takes in gas at nearly constant low back pressure near atmospheric pressure; introduces little or no back pressure into source of helium. Concept also extended to recycling of other gases.

Cook, Joseph

1996-01-01

274

Reduce, Reuse, and Recycle  

NSDL National Science Digital Library

Boys and girls, grab your nose-plugs because today we are going to be digging through some garbage! We use a lot of garbage; the average American throws away nearly four pounds everyday. That\\'s a whopping 1,600 pounds a year! That means that every year, EACH one of you toss enough trash to equal the weight of all the students in our class...COMBINED! That\\'s a lot of garbage. Our world is big, but you might not have realized just how small it really is when it comes to holding all this trash. Would you want garbage in your backyard? Your playground? The park? There\\'s only so many places to store our waste. So, what do we do? We RECYCLE! What Does It Mean To Recycle? Recycling is taking things we use and would normally through into the trash can and putting them in a separate container. Instead of going to the dump, it goes to a recycling plant. Things like paper, newspaper, cardboard, plastic, glass, and aluminum are all products ...

Nicole

2008-11-19

275

Fuels from Recycling Systems  

ERIC Educational Resources Information Center

Three systems, operating at sufficient scale, produce fuels that may be alternatives to oil and gas. These three recycling systems are: Black Clawson Fiberclaim, Franklin, Ohio; Union Carbide, South Charleston, West Virginia; and Union Electric, St. Louis, Missouri. These produce a wet fuel, a pyrolytic gas, and a dry fuel, respectively. (BT)

Tillman, David A.

1975-01-01

276

Minerals Yearbook, 1992: Materials Recycling.  

National Technical Information Service (NTIS)

A large variety of materials are recycled by different sectors of our society. The materials recycling that is mainly addressed in this writing is from waste that is generated after manufacturing and use. Included is recycling that is generally more obvio...

A. O. Tanner

1992-01-01

277

Recycling incineration: Evaluating the choices  

Microsoft Academic Search

Conflicts between proponents of municipal solid waste incineration and advocates of recycling have escalated with efforts to reduce the volume of waste that ends up in landfills. Central to this debate is competition for materials that are both combustible and recyclable. Environmental and economic concerns also play a major role. This book, produced by the Environmental Defense Fund, compares recycling

R. A. Denison; J. Ruston

1993-01-01

278

Recycling Behavior: A Multidimensional Approach  

ERIC Educational Resources Information Center

This work centers on the study of consumer recycling roles to examine the sociodemographic and psychographic profile of the distribution of recycling tasks and roles within the household. With this aim in mind, an empirical work was carried out, the results of which suggest that recycling behavior is multidimensional and comprises the undertaking…

Meneses, Gonzalo Diaz; Palacio, Asuncion Beerli

2005-01-01

279

21 CFR 573.180 - Anhydrous ammonia.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Anhydrous ammonia. 573.180 Section 573.180 Food and...Additive Listing § 573.180 Anhydrous ammonia. (a) The food additive anhydrous ammonia is applied directly to corn plant...

2010-04-01

280

21 CFR 573.180 - Anhydrous ammonia.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Anhydrous ammonia. 573.180 Section 573.180 Food and...Additive Listing § 573.180 Anhydrous ammonia. (a) The food additive anhydrous ammonia is applied directly to corn plant...

2009-04-01

281

46 CFR 154.1760 - Liquid ammonia.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Liquid ammonia. 154.1760 Section 154.1760 ...Operating Requirements § 154.1760 Liquid ammonia. The master shall ensure that no person sprays liquid ammonia into a cargo tank containing more...

2013-10-01

282

Optical fiber-based evanescent ammonia sensor  

Microsoft Academic Search

An optical fiber-based evanescent gaseous ammonia sensor is designed and developed. The sensing dye, bromocresol purple (BCP), is immobilized in the substitutional cladding using sol–gel process. The sensing properties of the optical fiber sensor to gaseous ammonia at room temperature are presented. This newly developed ammonia sensor exhibits good reversibility and repeatability. The effect of different carrier gases, argon, nitrogen,

Wenqing Cao; Yixiang Duan

2005-01-01

283

Update on cerebral uptake of blood ammonia.  

PubMed

Ammonia is believed to play a key role in the development of hepatic encephalopathy (HE) with increased formation of glutamine playing a central role. It has been debated whether blood ammonia enters the brain by passive diffusion and/or active transport by ion-transporters and that changes in blood pH could affect the blood-to-brain transfer of ammonia. It has also been proposed that the permeability-surface area product for ammonia across the blood-brain barrier (PSBBB) should be increased in cirrhosis and HE. In the present paper it is argued that changes in blood pH does not alter PSBBB for ammonia and the question of passive diffusion versus active transport of ammonia remains unresolved. Furthermore, recent studies do not find evidence for increased PSBBB for ammonia in cirrhosis. The main determent for cerebral uptake of blood ammonia (i.e. flux) is the arterial blood ammonia concentration. This means that the only way to protect the brain from hyperammonemia is by lowering blood ammonia, inhibit cerebral uptake of ammonia, or by manipulating cerebral ammonia metabolism so that less glutamine is produced. PMID:23479402

Sørensen, Michael

2013-06-01

284

Fabrication, Microstructure, Magnetic, and Recording Properties of Percolated Perpendicular Media  

Microsoft Academic Search

In this paper, a new type of perpendicular magnetic media which we have termed percolated perpendicular media is discussed. We present the method we used to fabricate the media as well as an energetic rationale for the driving force to produce the desired microstructure. The microstructures of samples with various amounts of oxide material are presented and the optimum one

David E. Laughlin; Yingguo Peng; Yue-Ling Qin; Mark Lin; Jian-Gang Zhu

2007-01-01

285

Analysis of percolation and seepage through paddy bunds  

Microsoft Academic Search

This study investigates percolation and seepage through the bunds of flat and terraced paddies. Field experiments were conducted in Hsin-Pu of Hsin-Chu County, Taiwan, to measure the soil water content of various types of bund. Measurements revealed that the soil was unsaturated along the sloped surface of the terrace. Experimental results also indicated that seepage face flow did not develop

Han-Chen Huang; Chen-Wuing Liu; Shih-Kai Chen; Jui-Sheng Chen

2003-01-01

286

Anomalous Aharonov-Bohm effect in percolating superconducting films  

Microsoft Academic Search

We have studied the superconducting transition in thin films of Pb and Al as a function of temperature and magnetic field. Examination of the films in a transmission electron microscope shows a percolative structure with typical small loop sizes of a few thousand angstroms in Pb and about a thousand in Al. An ac current passing through the sample is

A. Gerber; G. Deutscher

1989-01-01

287

Percolation induced heat transfer in deep unsaturated zones  

USGS Publications Warehouse

Subsurface temperature data from a borehole located in a desert wash were measured and used to delineate the conductive and advective heat transfer regimes, and to estimate the percolation quantity associated with the 1997-1998 El Ni??no precipitation. In an arid environment, conductive heat transfer dominates the variation of shallow subsurface temperature most of the time, except during sporadic precipitation periods. The subsurface time-varying temperature due to conductive heat transfer is highly correlated with the surface atmospheric temperature variation, whereas temperature variation due to advective heat transfer is strongly correlated with precipitation events. The advective heat transfer associated with precipitation and infiltration is the focus of this paper. Disruptions of the subsurface conductive temperature regime, associated with the 1997-1998 El Ni??no precipitation, were detected and used to quantify the percolation quantity. Modeling synthesis using a one-dimensional coupled heat and unsaturated flow model indicated that a percolation per unit area of 0.7 to 1.3 m height of water in two weeks during February 1998 was responsible for the observed temperature deviations down to a depth of 35.2 m. The reported study demonstrated quantitatively, for the first time, that the near surface temperature variation due to advective heat transfer can be significant at a depth greater than 10 m in unsaturated soils and can be used to infer the percolation amount in thick unsaturated soils.

Lu, N.; LeCain, G. D.

2003-01-01

288

Impact of complex geometries on the percolation in nanocomposites  

NASA Astrophysics Data System (ADS)

As utilization of nanocomposites (polymer matrix doped with a nanoparticle) expands, the prevalence of composites with complex morphologies is increasing. Nanocomposite materials are desirable in that the addition of a nanoparticle can produce a significant alteration in properties such as electrical conductivity, while retaining some of the processability associated with the neat polymer. Enhancements of the mechanical or electrical properties are dependent on the formation of continuous networks of particle within the composite volume. This percolation process may be significantly influenced by the specific geometry of the composite. In this work the nanostructure of interest is a mat of electrospun nanofibers with diameters of ˜100 nm and high porosity. To understand percolation within these mats, two series of Monte Carlo calculations are performed. The critical volume percent is investigated in continuous samples (purposefully non-complex structures) to determine the effect of sample size and shape; this is representative of the percolation in a single fiber. In addition, computational realizations of experimentally produced electrospun mats are tested for critical volume percentages; the aim being to establish which factors of the nanostructure influence the percolation process and how do these results compare to the continuous system.

Stevens, D. R.; Downen, L. N.; Clarke, L. I.

2008-10-01

289

Novel percolation phenomena and mechanism of strengthening elastomers by nanofillers.  

PubMed

Nano-strengthening by employing nanoparticles is necessary for high-efficiency strengthening of elastomers, which has already been validated by numerous researches and industrial applications, but the underlying mechanism is still an open challenge. In this work, we mainly focus our attention on studying the variation of the tensile strength of nanofilled elastomers by gradually increasing the filler content, within a low loading range. Interestingly, the percolation phenomenon is observed in the relationship between the tensile strength and the filler loading, which shares some similarities with the percolation phenomenon occurring in rubber toughened plastics. That is, as the loading of nanofillers (carbon black, zinc oxide) increases, the tensile strength of rubber nanocomposites (SBR, EPDM) increases slowly at first, then increases abruptly and finally levels off. Meanwhile, the bigger the particle size, the higher the filler content at the percolation point, and the lower the corresponding tensile strength of rubber nanocomposites. The concept of a critical particle-particle distance (CPD) is proposed to explain the observed percolation phenomenon. It is suggested that rubber strengthening through nanoparticles is attributed to the formation of stretched straight polymer chains between neighbor particles, induced by the slippage of adsorbed polymer chains on the filler surface during tension. Meanwhile, the factors to govern this CPD and the critical minimum particle size (CMPS) figured out in this work are both discussed and analyzed in detail. Within the framework of this percolation phenomenon, this paper also clearly answers two important and intriguing issues: (1) why is it necessary and essential to strengthen elastomers through nanofillers; (2) why does it need enough loading of nanofillers to effectively strengthen elastomers. Moreover, on the basis of the percolation phenomenon, we give out some guidance for reinforcement design of rubbery materials: the interfacial interactions between rubber and fillers cannot be complete chemical bonding, and partial physical absorption of macromolecular chains on the filler surface is necessary, otherwise the formation of stretched straight chains would be seriously hindered. There should exist such an optimum crosslinking density for a certain filler reinforced rubber system, and as well an optimum filler loading for rubber strengthening. Additionally, the different percolation behaviors of Young's modulus, the tensile strength and the electrical conductivity are compared and analyzed in our work. Lastly, molecular simulation indicates that it is not possible to strengthen glassy or hard polymer matrices by incorporating spherical nanoparticles. In general, by providing substantial experimental data and detailed analyses, this work is believed to promote the fundamental understanding of rubber reinforcement, as well provide better guidance for the design of high-performance and multi-functional rubber nanocomposites. PMID:20449394

Wang, Zhenhua; Liu, Jun; Wu, Sizhu; Wang, Wenchuan; Zhang, Liqun

2010-03-28

290

Integrated-optic ammonia sensor  

Microsoft Academic Search

Fibre coupled optical sensors for chemical and biologial species are important for process control, environmental control and pollution detection. An integrated optic ammonia sensor is described here; this is based on evanescent field absorption. The sensitive element of this sensor is a strip waveguide, fabricated by field assisted ion exchange, coated with a immobilized indicator dye. The sensor has a

Rainer Klein; Edgar Voges

1994-01-01

291

Hydrogen production using ammonia borane  

DOEpatents

Hydrogen ("H.sub.2") is produced when ammonia borane reacts with a catalyst complex of the formula L.sub.nM-X wherein M is a base metal such as iron, X is an anionic nitrogen- or phosphorus-based ligand or hydride, and L is a neutral ancillary ligand that is a neutral monodentate or polydentate ligand.

Hamilton, Charles W; Baker, R. Thomas; Semelsberger, Troy A; Shrestha, Roshan P

2013-12-24

292

THE OPTIMAL LOCATION OF TWO RECYCLING CENTERS  

Microsoft Academic Search

Suppose a municipality optimally locates two recycling\\/sorting centers to minimize the sum of the transportation costs from i) households to the recycling centers and ii) recycling centers to the landfill. Assume that all household waste is taken to a recycling center, sorted, and the non-recyclables are subsequently transported to the landfill. The landfill location and the proportion of waste recycled

Jannett Highfill; Michael McAsey; Libin Mou

293

Improved purification of Piscirickettsia salmonis using Percoll gradients.  

PubMed

Viable preparations of intact Piscirickettsia salmonis, purified from host cell material, are necessary for studying characteristics associated with this bacterium. However, purification of the organism is difficult due to its obligate intracellular nature. A simple and effective method for isolating whole P. salmonis, which is quick and easy to perform, but still maintains the viability and antigenicity of the bacterium is described. P. salmonis was purified by differential pelleting and density gradient centrifugation using 30%, 40%, or 50% (v/v) Percoll gradients. Following fractionation, a band with a density of 1.056-1.080 was found to be composed entirely of rickettsiae, confirmed by fluorescent antibody technique (IFAT). Purity of the P. salmonis from different stages of the purification process was assessed by light and transmission electron microscopy, and the viability of yields determined from a plaque assay and a tissue culture infective dose (TCID(50) ml(-1)). P. salmonis recovered from the 30% Percoll gradient appeared to retain their intracellular structure better than P. salmonis obtained from the 40% and 50% Percoll gradients, and appeared to have a greater viability. Differences were seen between P. salmonis-infected CHSE-214 cells and purified P. salmonis when compared by SDS-PAGE and Western blotting, and less host cell contamination was present in preparations obtained from the 30% Percoll gradient. Finally ten different P. salmonis isolates obtained from three different geographical locations and four different fish species, were purified using the 30% Percoll gradient. When the morphology of these was compared by transmission electron microscopy (TEM), they appeared similar in size and appearance, although isolate R980769 was highly pleomorphic and isolate R-29 was larger than the other isolates examined. PMID:16434115

Yuksel, S A; Thompson, K D; Ellis, A E; Adams, A

2006-08-01

294

Transcriptional Response of the Archaeal Ammonia Oxidizer Nitrosopumilus maritimus to Low and Environmentally Relevant Ammonia Concentrations  

PubMed Central

The ability of chemoautotrophic ammonia-oxidizing archaea to compete for ammonia among marine microorganisms at low ambient concentrations has been in part attributed to their extremely high affinity for ammonia, but as yet there is no mechanistic understanding of supporting metabolism. We examined transcription of selected genes for anabolic functions (CO2 fixation, ammonia transport, and cell wall synthesis) and a central catabolic function (ammonia oxidation) in the thaumarchaeon Nitrosopumilus maritimus SCM1 growing at two ammonia concentrations, as measured by combined ammonia and ammonium, one well above the Km for ammonia oxidation (?500 ?M) and the other well below the Km (<10 nM). Transcript levels were generally immediately and differentially repressed when cells transitioned from ammonia-replete to ammonia-limiting conditions. Transcript levels for ammonia oxidation, CO2 fixation, and one of the ammonia transport genes were approximately the same at high and low ammonia availability. Transcripts for all analyzed genes decreased with time in the complete absence of ammonia, but with various rates of decay. The new steady-state mRNA levels established are presumably more reflective of the natural physiological state of ammonia-oxidizing archaea and offer a reference for interpreting message abundance patterns in the natural environment.

Stahl, David A.

2013-01-01

295

COPPER CABLE RECYCLING TECHNOLOGY  

SciTech Connect

The United States Department of Energy (DOE) continually seeks safer and more cost-effective technologies for use in deactivation and decommissioning (D&D) of nuclear facilities. The Deactivation and Decommissioning Focus Area (DDFA) of the DOE's Office of Science and Technology (OST) sponsors large-scale demonstration and deployment projects (LSDDPs). At these LSDDPs, developers and vendors of improved or innovative technologies showcase products that are potentially beneficial to the DOE's projects and to others in the D&D community. Benefits sought include decreased health and safety risks to personnel and the environment, increased productivity, and decreased costs of operation. The Idaho National Engineering and Environmental Laboratory (INEEL) generated a list of statements defining specific needs and problems where improved technology could be incorporated into ongoing D&D tasks. One such need is to reduce the volume of waste copper wire and cable generated by D&D. Deactivation and decommissioning activities of nuclear facilities generates hundreds of tons of contaminated copper cable, which are sent to radioactive waste disposal sites. The Copper Cable Recycling Technology separates the clean copper from contaminated insulation and dust materials in these cables. The recovered copper can then be reclaimed and, more importantly, landfill disposal volumes can be reduced. The existing baseline technology for disposing radioactively contaminated cables is to package the cables in wooden storage boxes and dispose of the cables in radioactive waste disposal sites. The Copper Cable Recycling Technology is applicable to facility decommissioning projects at many Department of Energy (DOE) nuclear facilities and commercial nuclear power plants undergoing decommissioning activities. The INEEL Copper Cable Recycling Technology Demonstration investigated the effectiveness and efficiency to recycle 13.5 tons of copper cable. To determine the effectiveness of separating out radioactive contamination, the copper cable was coated with a surrogate contaminant. The demonstration took place at the Bonneville County Technology Center in Idaho Falls, Idaho.

Chelsea Hubbard

2001-05-01

296

Refrigerator recycling and CFCs  

Microsoft Academic Search

Utility-sponsored refrigerator and freezer pick-up programs have removed almost 900,000 inefficient appliances from the North American electric grid to date. While the CFC-12 refrigerant from the discarded appliances is typically removed and recycled, in all but a few programs the CFC-11 in the foam insulation is not. About a quarter-billion pounds of CFC-11 are banked in refrigerator foam in the

M. Shepard; W. Hawthorne; A. Wilson

1994-01-01

297

Percolation effects on entangled polymer rheology and the glass transition  

NASA Astrophysics Data System (ADS)

Current thinking on the fundamentals of entangled polymer melt rheology suggests that stress relaxation in the terminal zone occurs via Reptation, chain-end fluctuation and (convective) constraint release. This scenario is not correct. It is shown through a series of experiments with selectively deuterated model polymers that relaxation occurs through a percolation process which permits large clusters of entangled polymers to stress relax before their conformations are fully relaxed. The percolation model of entanglements (R.P. Wool, Macromolecules 26, 1564, 1993) makes unique predictions regarding the dynamics of polymer chains in the terminal relaxation zone. These include: (a) Reptating homopolymer chains with molecular weight M >> Mc appear to be non-Reptating as their ends and centers relax at the same rate in a Rouse-like manner during percolation. (b) The mechanical relaxation time ?(M) is related to the Reptation time Tr~ M3 by ?(M) = Tr[(1-Mc/M)Me/Mc]2, which is the origin of the zero shear viscosity behaving as ?o~M3.4 (c) The biggest surprise is that during stress relaxation, the random coil dimensions Rg(//) and Rg(?) are not fully relaxed when the stress and birefringence relax to zero. (d) Matrix molecular weight P effects on relaxation time ?(M) of the probe chain M are as follows: When the probe chain M>>P, the matrix P-chains percolate and Rouse-like dynamics is observed for the M-Reptating chains with ?(M) ~ P1M2. (e) When the matrix P>>M, percolation does not occur for the M-chain and the relaxation time of the probe chain ?(M) ~ PoM3 is in accord with DeGennes Reptation theory. These unusual results predicted by entanglement percolation are supported by extensive experimental data (NR, SANS, DSIMS, FTIR, BR) from selectively deuterated polystyrene chains HDH, DHD, HPS and DPS. These results clearly suggest that current notions of polymer rheology need to be reconsidered. Near Tg, a new perspective on the Glass Transition of amorphous materials is offered by the Twinkling Fractal Theory (TFT). [R. P. Wool, J. Polym. Sci, Part B: Polym Phys. 46, 2765 (2008)]. TFT applications to entangled polymers include: (a) rate dependence of dynamical mechanical properties, particularly the tan delta damping peak used to measure Tg, (b) derivation of the empirical WLF and Vogel Fulcher time-temperature superposition empirical relation, (c) Physical Aging and (d) Nanoconfinement.

Wool, Richard P.

2012-07-01

298

Municipal solid waste recycling issues  

SciTech Connect

Municipal solid waste (MSW) recycling targets have been set nationally and in many states. Unfortunately, the definitions of recycling, rates of recycling, and the appropriate components of MSW vary. MSW recycling has been found to be costly for most municipalities compared to landfill disposal. MSW recycling policy should be determined by the cost to the community and to society more generally. In particular, recycling is a good policy only if environmental impacts and the resources used to collect, sort, and recycle a material are less than the environmental impacts and resources needed to provide equivalent virgin material plus the resources needed to dispose of the postconsumer material safely. From a review of the existing economic experience with recycling and an analysis of the environmental benefits (including estimation of external social costs), the authors find that, for most communities, curbside recycling is only justifiable for some postconsumer waste, such as aluminum and other metals. They argue that alternatives to curbside recycling collection should be explored, including product takeback for products with a toxic content (such as batteries) or product redesign to permit more effective product remanufacture.

Lave, L.B.; Hendrickson, C.T.; Conway-Schempf, N.M.; McMichael, F.C. [Carnegie-Mellon Univ., Pittsburgh, PA (United States)] [Carnegie-Mellon Univ., Pittsburgh, PA (United States)

1999-10-01

299

Ammonia abundances in four comets  

NASA Technical Reports Server (NTRS)

NH2 emission band strengths were measured in four comets and the NH2 column densities were determined in order to measure the ammonia content of the comets. The mean ammonia/water abundance ratio derived for the four comets is found to be 0.13 + or - 0.06 percent, with no significant variation among the comets. The uniformity of this abundance attests to a remarkable degree of chemical homogeneity over large scales in the comet-forming region of the primordial solar nebula, and contrasts with the CO abundance variations found previously in comets. The N2 and NH3 abundances indicate a condensation temperature in the range 20-160 K, consistent with virtually all comet formation hypotheses.

Wickoff, Susan; Tegler, Stephen C.; Engel, Lisa

1991-01-01

300

Ammonium removal from wastewater via struvite pyrolysate recycling with Mg(OH)2 addition.  

PubMed

Magnesium ammonium phosphate (MAP) pyrolysate recycling technology was investigated with Mg(OH)2-mediated pyrolysis. The results revealed that the removal ratio of ammonium was stable at about 75%, and could be increased to 79% after additional acidolysis. The phosphate concentration in the supernate was low at 2 mg/L. The optimum conditions for ammonia release were a 1:1 molar ratio of Mg(OH)2:NH4(+), a heating temperature of 110 °C and a heating time of 3 h. With continual additions of Mg(OH)2 to release ammonia, magnesium phosphate (Mg3(PO4)2) was suggested as a possible derivative. However, with Mg(OH)2-mediated pyrolysis, the growth and nucleation of MAP was inhibited during MAP pyrolysate recycling. PMID:24355855

Yu, Rongtai; Cheng, Subin; Ren, Hongqiang; Wang, Yanru; Ding, Lili; Geng, Jinju; Xu, Ke; Zhang, Yan

2013-01-01

301

Fiber-Optic Ammonia Sensors  

NASA Technical Reports Server (NTRS)

Reversible, colorimetric fiber-optic sensors are undergoing development for use in measuring concentrations of ammonia in air at levels relevant to human health [0 to 50 parts per million (ppm)]. A sensor of this type includes an optical fiber that has been modified by replacing a portion of its cladding with a polymer coat that contains a dye that reacts reversibly with ammonia and changes color when it does so. The change in color is measured as a change in the amount of light transmitted from one end of the fiber to the other. Responses are reversible and proportional to the concentration of ammonia over the range from 9 to 175 ppm and in some cases the range of reversibility extends up to 270 ppm. The characteristic time for the response of a sensor to rise from 10 to 90 percent of full scale is about 25 seconds. These sensors are fully operational in pure carbon dioxide and are not adversely affected by humidity. This work was done by Michael T. Carter

Carter, Michael T.

2003-01-01

302

Vulnerability of networks: Fractional percolation on random graphs  

NASA Astrophysics Data System (ADS)

We present a theoretical framework for understanding nonbinary, nonindependent percolation on networks with general degree distributions. The model incorporates a partially functional (PF) state of nodes so that both intensity and extensity of error are characterized. Two connected nodes in a PF state cannot sustain the load and therefore break their link. We give exact solutions for the percolation threshold, the fraction of giant cluster, and the mean size of small clusters. The robustness-fragility transition point for scale-free networks with a degree distribution pk?k-? is identified to be ? =3. The analysis reveals that scale-free networks are vulnerable to targeted attack at hubs: a more complete picture of their Achilles' heel turns out to be not only the hubs themselves but also the edges linking them together.

Shang, Yilun

2014-01-01

303

Diffusion in lattice Lorentz gases with a percolation threshold  

NASA Astrophysics Data System (ADS)

A mean-field approximation for the diffusion coefficient in lattice Lorentz gases with an arbitrary mixture of pointlike stochastic scatterers in the low-density limit is proposed. In this approximation, the diffusion coefficient is directly related to the first return probability of the moving particle in the corresponding Cayley tree through an effective ring operator. A renormalization scheme for the approximate determination of the first return probability is constructed. The predictions of this mean-field theory and those of the repeated ring approximation (RRA) are compared with computer simulation results for models in which a fraction xB of the scatterers are deterministic backscatterers, so that the diffusion coefficient vanishes beyond a certain percolation threshold xcB. The approximation proposed in this paper is seen to be in good agreement with the simulation results, in contrast to the RRA, which already fails to give the correct percolation threshold.

Acedo, L.; Santos, A.

1999-08-01

304

Mesoscale modeling of intergranular bubble percolation in nuclear fuels  

NASA Astrophysics Data System (ADS)

Phase-field simulations are used to examine the variability of intergranular fission gas bubble growth and percolation on uranium dioxide grain boundaries on a mesoscopic length scale. Three key parameters are systematically varied in this study: the contact angle (or dihedral angle) defining the bubble shape, the initial bubble density on the grain boundary plane, and the ratio of the gas diffusivity on the grain boundary versus the grain interiors. The simulation results agree well with previous experimental data obtained for bubble densities and average bubble areas during coalescence events. Interestingly, the rate of percolation is found to be highly variable, with a large dependency on the contact angle and the initial bubble density and little-to-no dependency on the grain boundary gas diffusivity.

Millett, Paul C.; Tonks, Michael; Biner, S. B.

2012-04-01

305

Quantum percolation in cuprate high-temperature superconductors  

PubMed Central

Although it is now generally acknowledged that electron–phonon interactions cause cuprate superconductivity with Tc values ?100 K, the complexities of atomic arrangements in these marginally stable multilayer materials have frustrated both experimental analysis and theoretical modeling of the remarkably rich data obtained both by angle-resolved photoemission (ARPES) and high-resolution, large-area scanning tunneling microscopy (STM). Here, we analyze the theoretical background in terms of our original (1989) model of dopant-assisted quantum percolation (DAQP), as developed further in some two dozen articles, and apply these ideas to recent STM data. We conclude that despite all of the many difficulties, with improved data analysis it may yet be possible to identify quantum percolative paths.

Phillips, J. C.

2008-01-01

306

Temporal Percolation of the Susceptible Network in an Epidemic Spreading  

PubMed Central

In this work, we study the evolution of the susceptible individuals during the spread of an epidemic modeled by the susceptible-infected-recovered (SIR) process spreading on the top of complex networks. Using an edge-based compartmental approach and percolation tools, we find that a time-dependent quantity , namely, the probability that a given neighbor of a node is susceptible at time , is the control parameter of a node void percolation process involving those nodes on the network not-reached by the disease. We show that there exists a critical time above which the giant susceptible component is destroyed. As a consequence, in order to preserve a macroscopic connected fraction of the network composed by healthy individuals which guarantee its functionality, any mitigation strategy should be implemented before this critical time . Our theoretical results are confirmed by extensive simulations of the SIR process.

Valdez, Lucas Daniel; Macri, Pablo Alejandro; Braunstein, Lidia Adriana

2012-01-01

307

Percolation modeling of self-damaging of composite materials  

NASA Astrophysics Data System (ADS)

We propose the concept of autonomous self-damaging in “smart” composite materials, controlled by activation of added nanosize “damaging” capsules. Percolation-type modeling approach earlier applied to the related concept of self-healing materials, is used to investigate the behavior of the initial material's fatigue. We aim at achieving a relatively sharp drop in the material's integrity after some initial limited fatigue develops in the course of the sample's usage. Our theoretical study considers a two-dimensional lattice model and involves Monte Carlo simulations of the connectivity and conductance in the high-connectivity regime of percolation. We give several examples of local capsule-lattice and capsule-capsule activation rules and show that the desired self-damaging property can only be obtained with rather sophisticated “smart” material's response involving not just damaging but also healing capsules.

Domanskyi, Sergii; Privman, Vladimir

2014-07-01

308

Percolation of interacting classical dimers on the square lattice  

NASA Astrophysics Data System (ADS)

We study the percolation properties of the interacting classical dimer model on the square lattice by means of Monte Carlo simulations and finite-size scaling analysis. We define Ising clusters based on the dimer configuration; the percolation point of the clusters coincides with the critical point of the Kosterlitz–Thouless transition of the dimer model, which is Tc=0.654(2). Furthermore, we find that the largest cluster at the Kosterlitz–Thouless point is a fractal, with fractal dimension Dc=1.874(2), which coincides with the critical exponent describing the critical behavior of the dimer–dimer correlation function, which is theoretically predicted to be 15/8.

Li, Yang; Wu, Dayan; Huang, Xianshan; Ding, Chengxiang

2014-06-01

309

Percolation of annotation errors through hierarchically structured protein sequence databases.  

PubMed

Databases of protein sequences have grown rapidly in recent years as a result of genome sequencing projects. Annotating protein sequences with descriptions of their biological function ideally requires careful experimentation, but this work lags far behind. Instead, biological function is often imputed by copying annotations from similar protein sequences. This gives rise to annotation errors, and more seriously, to chains of misannotation. [Percolation of annotation errors in a database of protein sequences (2002)] developed a probabilistic framework for exploring the consequences of this percolation of errors through protein databases, and applied their theory to a simple database model. Here we apply the theory to hierarchically structured protein sequence databases, and draw conclusions about database quality at different levels of the hierarchy. PMID:15748731

Gilks, Walter R; Audit, Benjamin; de Angelis, Daniela; Tsoka, Sophia; Ouzounis, Christos A

2005-02-01

310

Unusual percolation in simple small-world networks.  

PubMed

We present an exact solution of percolation in a generalized class of Watts-Strogatz graphs defined on a one-dimensional underlying lattice. We find a nonclassical critical point in the limit of the number of long-range bonds in the system going to zero, with a discontinuity in the percolation probability and a divergence in the mean finite-cluster size. We show that the critical behavior falls into one of three regimes depending on the proportion of occupied long-range to unoccupied nearest-neighbor bonds, with each regime being characterized by different critical exponents. The three regimes can be united by a single scaling function around the critical point. These results can be used to identify the number of long-range links necessary to secure connectivity in a communication or transportation chain. As an example, we can resolve the communication problem in a game of "telephone." PMID:19658569

Cohen, Reuven; Dawid, Daryush Jonathan; Kardar, Mehran; Bar-Yam, Yaneer

2009-06-01

311

Percolation model of polydisperse composite solid propellant combustion  

SciTech Connect

The composition dependence of the burn rate of polydisperse composite solid propellants is predicted by analyzing the least-time path of the burn front through the propellant. The predicted burn rate is the average burn rate along the least-time path divided by the tortuosity, or arc length per streamwise interval, of the least-time path. The tortuosity analysis is based on percolation theory. Aspects of percolation theory which are pertinent to the analysis are introduced in a self-contained Appendix. The model, which contains four adjustable parameters, is validated by comparison to measured burn rates for a suite of polydisperse ammonium perchlorate composites. The data correlations are found to be significantly better than for a three-parameter version of the model which omits tortuosity considerations.

Kerstein, A.R.

1987-07-01

312

Nonuniversality of invasion percolation in two-dimensional systems.  

PubMed

Employing highly efficient algorithms for simulating invasion percolation (IP) with trapping, we obtain precise estimates for the fractal dimensions of the sample-spanning cluster, the backbone, and the minimal path in a variety of two-dimensional lattices. The results indicate that these quantities are nonuniversal and vary with the coordination number Z of the lattices. In particular, while the fractal dimension D(f) of the sample-spanning cluster in lattices with low Z has the generally accepted value of about 1.82, it crosses over to the value of random percolation, D(f) approximately equal to 1.896, if Z is large enough. Since optimal paths in strongly disordered media and minimum spanning trees on random graphs are related to IP, the implication is that these problems do not also possess universal scaling properties. PMID:11909136

Knackstedt, Mark A; Sahimi, Muhammad; Sheppard, Adrian P

2002-03-01

313

Minimal spanning trees at the percolation threshold: a numerical calculation.  

PubMed

The fractal dimension of minimal spanning trees on percolation clusters is estimated for dimensions d up to d=5. A robust analysis technique is developed for correlated data, as seen in such trees. This should be a robust method suitable for analyzing a wide array of randomly generated fractal structures. The trees analyzed using these techniques are built using a combination of Prim's and Kruskal's algorithms for finding minimal spanning trees. This combination reduces memory usage and allows for simulation of larger systems than would otherwise be possible. The path length fractal dimension d_{s} of MSTs on critical percolation clusters is found to be compatible with the predictions of the perturbation expansion developed by T. S. Jackson and N. Read [Phys. Rev. E 81, 021131 (2010)]. PMID:24125235

Sweeney, Sean M; Middleton, A Alan

2013-09-01

314

Percolation in aggregates of nanoclusters immersed in superfluid helium  

NASA Astrophysics Data System (ADS)

Impurity-helium condensates created by injection of hydrogen (deuterium) atoms and molecules as well as rare gas (RG) atoms (Ne and Kr) into superfluid He4 have been studied via electron spin resonance (ESR) techniques. Measurements of the ground-state spectroscopic parameters of hydrogen and deuterium atoms show that the nanoclusters have a shell structure. H and D atoms reside in solid molecular layers of H2 and D2, respectively. These layers form on the surfaces of RG (Ne or Kr) nanoclusters. By monitoring the recombination of H atoms in the collection of hydrogen-neon nanoclusters, we show that nanoclusters form a gel-like porous structure which enables the H atoms to be transported through the structure via percolation. Observation of percolation in the collection of nanoclusters containing stabilized hydrogen atoms may open possibilities for a search for macroscopic collective quantum phenomena at ultralow temperatures accessible by a dilution refrigerator.

Mao, S.; Meraki, A.; Boltnev, R. E.; Khmelenko, V. V.; Lee, D. M.

2014-04-01

315

Percolative diffusion of CO during CO oxidation on Pt(100)  

SciTech Connect

During CO-oxidation on Pt(100), CO diffuses in a {open_quote}{open_quote}disordered environment{close_quote}{close_quote} produced by a complex pattern of reconstructed and unreconstructed regions of the substrate. Macroscopic diffusion of CO is effectively only possible on percolating 1{times}1-regions of the substrate. We treat the spatio-temporal behavior observed in this reaction system accounting in the simple way for the percolative nature of CO-diffusion. This is done via incorporation into the reaction-diffusion equations of a suitable chemical diffusion coefficient, exploiting ideas from the theory of transport in disordered media. We use these equations to analyze the propagation of reactive, O-rich pulses into a CO-covered 1{times}1-background. {copyright} {ital 1996 American Institute of Physics.}

Tammaro, M. [Ames Laboratory and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States); Evans, J.W. [Ames Laboratory and Department of Mathematics, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory and Department of Mathematics, Iowa State University, Ames, Iowa 50011 (United States)

1996-03-01

316

Percolation approach to initial stage effects in high energy collisions  

NASA Astrophysics Data System (ADS)

Possible phase transition of strongly interacting matter from hadron to a quark-gluon plasma state have in the past received considerable interest. The clustering of color sources provides a framework of the partonic interactions in the initial stage of the collisions. The onset of deconfinement transition is identified by the spanning percolation cluster in 2D percolation. In this talk results are presented both for the multiplicity and the elliptic flow at RHIC and LHC energies. The thermodynamic quantities temperature, equation of state and transport coefficient are obtained in the framework of clustering of color sources. It is shown that the results are in excellent agreement with the recent lattice QCD calculations (LQCD).

Srivastava, Brijesh K.

2014-06-01

317

Temporal percolation of the susceptible network in an epidemic spreading.  

PubMed

In this work, we study the evolution of the susceptible individuals during the spread of an epidemic modeled by the susceptible-infected-recovered (SIR) process spreading on the top of complex networks. Using an edge-based compartmental approach and percolation tools, we find that a time-dependent quantity ?S(t), namely, the probability that a given neighbor of a node is susceptible at time t, is the control parameter of a node void percolation process involving those nodes on the network not-reached by the disease. We show that there exists a critical time t(c) above which the giant susceptible component is destroyed. As a consequence, in order to preserve a macroscopic connected fraction of the network composed by healthy individuals which guarantee its functionality, any mitigation strategy should be implemented before this critical time t(c). Our theoretical results are confirmed by extensive simulations of the SIR process. PMID:23028498

Valdez, Lucas Daniel; Macri, Pablo Alejandro; Braunstein, Lidia Adriana

2012-01-01

318

Dimensional Analysis of Percolation Theory: Applications to Polymer Composites  

NASA Astrophysics Data System (ADS)

Percolation theory is well known to describe functional phenomena in polymer composites such as electrical conductivity, when combining a conducting particle and insulating matrix. Nanostructured composites can, however, present unique morphologies that are not easily described by the typical one, two, or three-dimensional viewpoint. One example is random mats of polymer/carbon nanotube (or silver nanoparticle) composite nanofibers. With this motivation, Monte Carlo simulations were developed to investigate various effects within such a fibrous geometry, including changes to the critical volume fraction due to the dimensionality: particle aspect ratio, relative size of particle and fiber (or film), sample size, continuous vs. porous structure. From these simulations a model was developed to predict the percolation threshold based on the dimensionality of the system. The results of these simulations and the derived model will be presented.

Stevens, Derrick; Hoffman, Torissa; Gorga, Russell; Clark, Laura

2008-03-01

319

Why recycle? A comparison of recycling motivations in four communities  

NASA Astrophysics Data System (ADS)

Four Illinois communities with different sociode-mographic compositions and at various stages of planning for solid waste management were surveyed to determine the influence of sociodemographic variables and planning stages on the factors that motivate recycling behavior. A factor analysis of importance ratings of reasons for recycling and for not recycling yielded five factors interpreted as altruism, personal inconvenience, social influences, economic incentives, and household storage. The four communities were shown to be significantly different in multivariate analyses of the five motivational factors. However, attempts to explain these community differences with regression analyses, which predicted the motivational factors with dummy codes for planning stages, a measure of self-reported recycling behavior, and sociodemographic measures were unsatisfactory. Contrary to expectation, the solid waste management planning stages of the cities (curbside pickup, recycling dropoff center, and planning in progress) contributed only very slightly to the prediction of motivational factors for recycling. Community differences were better explained by different underlying motivational structures among the four communities. Altruistic reasons for recycling (e.g., conserving resources) composed the only factor which was similar across the four communities. This factor was also perceived to be the most important reason for recycling by respondents from all four communities. The results of the study supported the notion that convenient, voluntary recycling programs that rely on environmental concern and conscience for motivation are useful approaches to reducing waste.

Vining, Joanne; Linn, Nancy; Burdge, Rabel J.

1992-11-01

320

Understanding recycling behavior in Kentucky: Who recycles and why  

NASA Astrophysics Data System (ADS)

Recycling behavior and the motivations behind recycling are being analyzed in a collaborative study between the Sloan Industry Center for a Sustainable Aluminum Industry, the Center for Aluminum Technology, Secat, and the Gatton College of Business and Economics at the University of Kentucky in Lexington. The goals of this study are to determine why people recycle and to find ways to motivate people to recycle more, using Fayette County, Kentucky, as a sample study. It is hoped that the information gathered through educational and motivational efforts in this county can be used on a larger scale in communities throughout the United States.

Morgan, Fred W.; Hughes, Margaret V.

2006-08-01

321

Percolation in networks with long-range connections  

NASA Astrophysics Data System (ADS)

Two-dimensional lattices of points are connected with long-range links, whose lengths are distributed according to P(r)?r. By changing the decay exponent ? one can go from d-dimensional short-range networks to ?-dimensional networks topologically similar to random graphs. Percolation on these networks is numerically studied for systems of up to 107 sites. The shortest-path, fractal and chemical dimensions are determined at the critical threshold, as a function of the decay exponent ?.

Moukarzel, Cristian F.

2006-12-01

322

Rapidity long range correlations, parton percolation and color glass condensate  

SciTech Connect

The similarities between string percolation and Glasma results are emphasized, special attention being paid to rapidity long range correlations, ridge structure and elliptic flow. As the string density of high multiplicity pp collisions at LHC energies has similar value as the corresponding to Au-Au semi-central collisions at RHIC we also expect in pp collisions long rapidity correlations and ridge structure, extended more than 8 units in rapidity.

Bautista, I.; Pajares, C. [IGFAE and Departamento de Fisica de Particulas, Univ. of Santiago de Compostela, 15782, Santiago de Compostela (Spain); Dias de Deus, J. [CENTRA, Departamento de Fisica, IST, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

2011-05-23

323

Transfer matrix computation of generalized critical polynomials in percolation  

NASA Astrophysics Data System (ADS)

Percolation thresholds have recently been studied by means of a graph polynomial PB(p), henceforth referred to as the critical polynomial, that may be defined on any periodic lattice. The polynomial depends on a finite subgraph B, called the basis, and the way in which the basis is tiled to form the lattice. The unique root of PB(p) in [0, 1] either gives the exact percolation threshold for the lattice, or provides an approximation that becomes more accurate with appropriately increasing size of B. Initially PB(p) was defined by a contraction-deletion identity, similar to that satisfied by the Tutte polynomial. Here, we give an alternative probabilistic definition of PB(p), which allows for much more efficient computations, by using the transfer matrix, than was previously possible with contraction-deletion. We present bond percolation polynomials for the (4, 82), kagome, and (3, 122) lattices for bases of up to respectively 96, 162 and 243 edges, much larger than the previous limit of 36 edges using contraction-deletion. We discuss in detail the role of the symmetries and the embedding of B. For the largest bases, we obtain the thresholds pc(4, 82) = 0.676?803?329…, pc(kagome) = 0.524?404?998…, pc(3, 122) = 0.740?420?798…, comparable to the best simulation results. We also show that the alternative definition of PB(p) can be applied to study site percolation problems. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.

Scullard, Christian R.; Lykke Jacobsen, Jesper

2012-12-01

324

Vector Percolation Analysis of Triglyceride-based Thermoset Polymers  

NASA Astrophysics Data System (ADS)

Thermosetting Acrylated triglycerides (ATG) were prepared from various oils and model triglycerides. The distribution of acrylate groups was calculated from the distribution of unsaturation sites on unmodified oils, assuming a binomial distribution of acrylate groups. The ATG were both homopolymerized and copolymerized with styrene. The cross-link density v, of the polymers was calculated using the recursive method of Miller and Macosko from a knowledge of the acrylate distribution. The cross-link density was found to increase with the level of acrylation A, in a vector percolation manner, and the trends in the cross-link density predictions matched the experimental results. The deviation in the experimental results and model predictions were the result of intramolecular cross-linking. Approximately 0.5 and 0.8 acrylates per triglyceride were lost to intramolecular cyclization for homopolymerized acrylated triglycerides and triglycerides copolymerized with styrene, respectively. Equations for the level of perfection p, of the triglyceride networks and the percolation threshold pc, were developed using the calculated number of acrylates lost to cyclization. Polymers with p < 0.1 without styrene, and p < 0.39 with styrene did not have mechanical integrity, validating the definition of the level of perfection and percolation threshold pc. The tensile strength, S ˜ [p-p]^1/2 and modulus E ˜ [p-pc]^3 , were in accord with vector percolation theory, where p could be derived experimentally via A ˜ [p-pc] , v ˜ A and FTIR analysis of the extent of reaction of the C=C groups. These results also indicated how mechanical properties were controlled by the fatty acid distribution function of the plant oils, and which oil would give the best particular property. Supported by EPA and DoE.

Lascala, John J.; Wool, Richard P.

2003-03-01

325

Percolating contact subnetworks on the edge of isostaticity  

Microsoft Academic Search

We search for a percolating, strong subnetwork of contacts in a quasi-statically deforming, frictional granular material.\\u000a Of specific interest in this study is that subnetwork which contributes to the majority of the total deviator stress and is,\\u000a or is on the edge of being, isostatic. We argue that a subnetwork derived from the minimal spanning trees of a graph—optimized\\u000a to

David M. Walker; Antoinette Tordesillas; Colin Thornton; Robert P. Behringer; Jie Zhang; John F. Peters

2011-01-01

326

Controlling electrical percolation in multicomponent carbon nanotube dispersions.  

PubMed

Carbon nanotube reinforced polymeric composites can have favourable electrical properties, which make them useful for applications such as flat-panel displays and photovoltaic devices. However, using aqueous dispersions to fabricate composites with specific physical properties requires that the processing of the nanotube dispersion be understood and controlled while in the liquid phase. Here, using a combination of experiment and theory, we study the electrical percolation of carbon nanotubes introduced into a polymer matrix, and show that the percolation threshold can be substantially lowered by adding small quantities of a conductive polymer latex. Mixing colloidal particles of different sizes and shapes (in this case, spherical latex particles and rod-like nanotubes) introduces competing length scales that can strongly influence the formation of the system-spanning networks that are needed to produce electrically conductive composites. Interplay between the different species in the dispersions leads to synergetic or antagonistic percolation, depending on the ease of charge transport between the various conductive components. PMID:21478868

Kyrylyuk, Andriy V; Hermant, Marie Claire; Schilling, Tanja; Klumperman, Bert; Koning, Cor E; van der Schoot, Paul

2011-06-01

327

A chemical percolation model for coal devolatilization: Milestone report  

SciTech Connect

The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated coal based on the chemical structure of the parent coal. This document provides complete details of the development of the CPD model. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the infinite coal lattice. The chemical percolation devolatilization model described here includes treatment of vapor- liquid equilibrium and a crosslinking mechanism. The crosslinking mechanism permits reattachment of metaplast to the infinite char matrix. A generalized vapor pressure correlation for high molecular weight hydrocarbons, such as coal tar, is proposed based on data from coal liquids. Coal-independent kinetic parameters are employed. Coal-dependent chemical structure coefficients for the CPD model are taken directly from {sup 13}C NMR measurements, with the exception of one empirical parameter representing the population of char bridges in the parent coal. This is in contrast to the previous and common practice of adjusting input coefficients to precisely match measured tar and total volatiles yields.

Fletcher, T.H.; Kerstein, A.R. (Sandia National Labs., Livermore, CA (United States)); Pugmire, R.J.; Solum, M.; Grant, D.M. (Utah Univ., Salt Lake City, UT (United States))

1992-05-01

328

Theory of percolation and tunneling regimes in nanogranular metal films  

NASA Astrophysics Data System (ADS)

Nanogranular metal composites, consisting of immiscible metallic and insulating phases deposited on a substrate, are characterized by two distinct electronic transport regimes depending on the relative amount of the metallic phase. At sufficiently large metallic loadings, granular metals behave as percolating systems with a well-defined critical concentration above which macroscopic clusters of physically connected conductive particles span the entire sample. Below the critical loading, granular metal films are in the dielectric regime, where current can flow throughout the composite only via hopping or tunneling processes between isolated nanosized particles or clusters. In this case transport is intrinsically nonpercolative in the sense that no critical concentration can be identified for the onset of transport. It is shown here that, although being very different in nature, these two regimes can be described by treating percolation and hopping on equal footing. By considering general features of the microstructure and of the electrical connectedness, the concentration dependence of the dc conductivity of several nanogranular metal films is reproduced to high accuracy within an effective-medium approach. In particular, fits to published experimental data enable us to extract the values of microscopic parameters that govern the percolation and tunneling regimes, explaining thus the transport properties observed in nanogranular metal films.

Grimaldi, Claudio

2014-06-01

329

Loopless nontrapping invasion-percolation model for fracking  

NASA Astrophysics Data System (ADS)

Recent developments in hydraulic fracturing (fracking) have enabled the recovery of large quantities of natural gas and oil from old, low-permeability shales. These developments include a change from low-volume, high-viscosity fluid injection to high-volume, low-viscosity injection. The injected fluid introduces distributed damage that provides fracture permeability for the extraction of the gas and oil. In order to model this process, we utilize a loopless nontrapping invasion percolation previously introduced to model optimal polymers in a strongly disordered medium and for determining minimum energy spanning trees on a lattice. We performed numerical simulations on a two-dimensional square lattice and find significant differences from other percolation models. Additionally, we find that the growing fracture network satisfies both Horton-Strahler and Tokunaga network statistics. As with other invasion percolation models, our model displays burst dynamics, in which the cluster extends rapidly into a connected region. We introduce an alternative definition of bursts to be a consecutive series of opened bonds whose strengths are all below a specified value. Using this definition of bursts, we find good agreement with a power-law frequency-area distribution. These results are generally consistent with the observed distribution of microseismicity observed during a high-volume frack.

Norris, J. Quinn; Turcotte, Donald L.; Rundle, John B.

2014-02-01

330

Reversible intercalation of ammonia molecules into a layered double hydroxide structure without exchanging nitrate counter-ions  

SciTech Connect

A zinc/aluminum LDH was precipitated with recycled ammonia from a chemical vapor deposition reaction. The LDH presented a crystalline phase with basal distance of 8.9 A, typical for nitrate-containing LDHs, and another phase with a basal distance of 13.9 A. Thermal treatment at 150 {sup o}C eliminated the phase with the bigger basal distance leaving only the anhydrous nitrate-intercalated LDH structure with 8.9 A. Intense N-H stretching modes in the FTIR spectra suggested that the expansion was due to intercalation of ammonia in the form of [NH{sub 4}(NH{sub 3}){sub n}]{sup +} species. When additional samples were precipitated with pure ammonia, the conventional LDH nitrate structure was obtained (8.9 A basal distance) at pH=7, as well as a pure crystalline phase with 13.9 A basal distance at pH=10 due to ammonia intercalation that can be removed by heating at 150 {sup o}C or by stirring in acetone, confirming a unusual sensu stricto intercalation process into a LDH without exchanging nitrate ions. - Graphical abstract: LDH-nitrate precipitated with ammonia expands the interlayer space if ammonia is bubbled up to pH 10. The basal distance decreased when the compound was heated at 150 {sup o}C or stirred in acetone. Nitrate ions are not exchanged.

Carbajal Arizaga, Gregorio Guadalupe, E-mail: gregoriocarbajal@yahoo.com.m [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Km. 107 Carretera Tijuana-Ensenada, Apdo. Postal 14, C.P. 22800. Ensenada, Baja California (Mexico); Wypych, Fernando [CEPESQ-Research Centre of Applied Chemistry, Department of Chemistry, Federal University of Parana, P.O. Box 19081, 81531-980 Curitiba, PR (Brazil); Castillon Barraza, Felipe; Contreras Lopez, Oscar Edel [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Km. 107 Carretera Tijuana-Ensenada, Apdo. Postal 14, C.P. 22800. Ensenada, Baja California (Mexico)

2010-10-15

331

Thermodynamic Properties of Aqueous Solution of Ammonia  

NASA Astrophysics Data System (ADS)

Present status on the thermodynamic properties of experimental data and their correlations of both ammonia and aqueous solution of ammonia was introduced in this paper. The aqueous solution of ammonia is used for not only a working fluid in absorption refrigerator cycles but also working fluids in bottoming cycles of steam power plants and other heat recovering systems. Therefore, the thermodynamic properties of this substance are required in a wide range of temperatures, pressures and compositions. The experimental results of pVTx properties for ammonia and aqueous solution of ammonia and their comparisons with a formulation by Tillner-Roth and Friend1) were critically surveyed. The “Guideline on the IAPWS Formulation 2000 for the Thermodynamic Properties of Ammonia-Water Mixtures”, correlated by Tillner-Roth and Friend1), was approved on September, 2001, by the International Association for the Properties of Water and Steam (IAPWS) 2).

Kitamura, Hiroshi; Oguchi, Kosei

332

Ammonia and ammonium hydroxide sensors for ammonia/water absorption machines: Literature review and data compilation.  

National Technical Information Service (NTIS)

This report describes an evaluation of various sensing techniques for determining the ammonia concentration in the working fluid of ammonia/water absorption cycle systems. The purpose of this work was to determine if any existing sensor technology or inst...

N. C. Anheier C. E. McDonald J. M. Cuta F. M. Cuta K. B. Olsen

1995-01-01

333

Recycler barrier RF buckets  

SciTech Connect

The Recycler Ring at Fermilab uses a barrier rf systems for all of its rf manipulations. In this paper, I will give an overview of historical perspective on barrier rf system, the longitudinal beam dynamics issues, aspects of rf linearization to produce long flat bunches and methods used for emittance measurements of the beam in the RR barrier rf buckets. Current rf manipulation schemes used for antiproton beam stacking and longitudinal momentum mining of the RR beam for the Tevatron collider operation are explained along with their importance in spectacular success of the Tevatron luminosity performance.

Bhat, C.M.; /Fermilab

2011-03-01

334

Energy and Recycling  

NSDL National Science Digital Library

Energy and Garbage is one section of a US Department of Energy's educational Web site for kids. Features of this Web site include a section detailing the connection between energy and garbage, a thorough introduction to the history of garbage that includes facts and figures on how much waste we produce, information on recycling and reducing garbage at the source, and much more. The information in this Web site is presented in a friendly, narrative style. A short downloadable activity titled Energy from Garbage, created by the National Energy Education Development Project, is also available (grades 4-6).

335

Adsorption of ammonia on multilayer iron phthalocyanine  

SciTech Connect

The adsorption of ammonia on multilayers of well-ordered, flat-lying iron phthalocyanine (FePc) molecules on a Au(111) support was investigated by x-ray photoelectron spectroscopy. We find that the electron-donating ammonia molecules coordinate to the metal centers of iron phthlalocyanine. The coordination of ammonia induces changes of the electronic structure of the iron phthalocyanine layer, which, in particular, lead to a modification of the FePc valence electron spin.

Isvoranu, Cristina; Knudsen, Jan; Ataman, Evren; Andersen, Jesper N.; Schnadt, Joachim [Division of Synchrotron Radiation Research, Department of Physics, Lund University, Box 118, 221 00 Lund (Sweden); Schulte, Karina [MAX-lab, Lund University, Box 118, 221 00 Lund (Sweden); Wang Bin; Bocquet, Marie-Laure [Laboratoire de chimie, Ecole normale superieure de Lyon, 46, Allee d'Italie, 69364 Lyon Cedex 07 (France)

2011-03-21

336

A polypyrrole-based amperometric ammonia sensor  

Microsoft Academic Search

An ammonia sensor is described in this work. The sensing membrane is a thin layer of oxidized polypyrrole (PPy) on a platinum substrate. This sensor is used as the working electrode in a conventional three-electrode system for amperometric measurement of ammonia in aqueous solutions in the potential range of + 0.2 to + 0.4 V (vs. Ag\\/AgCl). Contact with ammonia

Ilkka Lähdesmäki; Andrzej Lewenstam; Ari Ivaska

1996-01-01

337

Polyaniline-based optical ammonia detector  

DOEpatents

Electronic absorption spectroscopy of a polyaniline film deposited on a polyethylene surface by chemical oxidation of aniline monomer at room temperature was used to quantitatively detect ammonia gas. The present optical ammonia gas detector was found to have a response time of less than 15 s, a regeneration time of less than 2 min. at room temperature, and a detection limit of 1 ppm (v/v) for ammonia, with a linear dynamic range from 180 ppm to 18,000 ppm.

Duan, Yixiang (Los Alamos, NM); Jin, Zhe (Los Alamos, NM); Su, Yongxuan (Los Alamos, NM)

2002-01-01

338

Ammonia Assimilation by Rhizobium Cultures and Bacteroids  

Microsoft Academic Search

SUMMARY The enzymes involved in the assimilation of ammonia by free-living cultures of Rhizobium spp. are glutamine synthetase (EC. 6.3. I. 2), glutamate synthase (L- glutamine : a-oxoglutarate amino transferase) and glutamate dehydrogenase (EC I.4. I.4). Under conditions of ammonia or nitrate limitation in a chemostat the assimilation of ammonia by cultures of R. leguminosarum, R. trifolii and R. japonicum

C. M. BROWN; M. J. DILWORTH

1975-01-01

339

Estimating ammonia emission factors in Europe. Summary of the work of the UNECE ammonia expert panel  

NASA Astrophysics Data System (ADS)

The UNECE ammonia expert panel presents emission factors for the ammonia emissions from agriculture. Included are emissions from animal husbandry (housing, storage of the wastes outside the building, grazing and application of the wastes), application of fertilizers to crops and grasslands, stubble burning of agricultural residues and finally ammonia emissions from latrines.

Van Der Hoek, K. W.

340

Stability of Aqueous Solutions of Hcn in the Presence of Ammonia or Ammonia and CO2.  

National Technical Information Service (NTIS)

The stability of aqueous solutions of HCN in the presence of ammonia or ammonia and CO2 was studied as one link in the fundamental research concerning the separation of HCN and ammonia from HCN synthetic gas without using sulfuric acid. The effects of the...

S. Fujise S. Nagai T. Numata

1973-01-01

341

CFC recycling system  

SciTech Connect

This patent describes a method for recycling freon. It comprises attaching a freon removal valve to a freon supply located in an appliance such as an air conditioner, refrigerator, freezer or the like, positioning a substantially empty freon collecting vessel in gas flow relationship to the valve by providing the freon removal valve with a puncture needle extending upwardly and adapted to puncture a freon supply tubing in the appliance, below the puncture needle is positioned a spring means, and below the spring means is positioned a piercing means adapted to pierce a closure in the collecting vessel to thereby establish a gas passage means extending from the supply tube, through the needle, through the piercing means to the collecting vessel, collecting the freon thereby in the collecting vessel, providing a substantially gas-free sealing means on the collecting vessel to insure substantial total containment of the freon within the collecting vessel, and delivering the collecting vessel to a collection center for reuse and recycling of the freon.

Furmanek, D.J.

1991-06-25

342

40 CFR 141.76 - Recycle provisions.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Recycle provisions. 141.76 Section 141...Filtration and Disinfection § 141.76 Recycle provisions. (a) Applicability...or direct filtration treatment and that recycle spent filter backwash water,...

2010-07-01

343

40 CFR 141.76 - Recycle provisions.  

Code of Federal Regulations, 2010 CFR

...and Disinfection] [Sec. 141.76 - Recycle provisions.] 40 PROTECTION OF ENVIRONMENT...Filtration and Disinfection Sec. 141.76 Recycle provisions. (a) Applicability. All...or direct filtration treatment and that recycle spent filter backwash water,...

2009-07-01

344

State Strategy for Recycling Market Development.  

National Technical Information Service (NTIS)

The ultimate importance of developing recycling markets is to accomplish these five objectives: Assist local governments and state offices in achieving the recycling goals in the SCORE (Select Committee on Recycling and the Environment) legislation throug...

L. Millberg

1991-01-01

345

Enhanced electrical properties in percolative low-density polyethylene\\/carbon nanotubes nanocomposites  

Microsoft Academic Search

Enhanced dielectric permittivity and conductivity are observed in low-density polyethylene\\/multiwall carbon nanotubes (LDPE\\/MWCNT) nanocomposites prepared via a melt-blending process and subsequent a hot-molding procedure when the volume fraction of MWCNT is near the percolation threshold. In comparison to some reported results, the present percolation threshold is high. The high percolation threshold may be attributed to the MWCNT, which are fractured

Hong-Tao Song; Zhi-Min Dang; Jing Lv; Sheng-Hong Yao; Jun-Wei Zha; Yi Yin

2010-01-01

346

Bacterial cell-wall recycling  

PubMed Central

Many Gram-negative and Gram-positive bacteria recycle a significant proportion of the peptidoglycan components of their cell walls during their growth and septation. In many—and quite possibly all—bacteria, the peptidoglycan fragments are recovered and recycled. While cell-wall recycling is beneficial for the recovery of resources, it also serves as a mechanism to detect cell-wall–targeting antibiotics and to regulate resistance mechanisms. In several Gram-negative pathogens, anhydro-MurNAc-peptide cell-wall fragments regulate AmpC ?-lactamase induction. In some Gram-positive organisms, short peptides derived from the cell wall regulate the induction of both ?-lactamase and ?-lactam-resistant penicillin-binding proteins. The involvement of peptidoglycan recycling with resistance regulation suggests that inhibitors of the enzymes involved in the recycling might synergize with cell-wall-targeted antibiotics. Indeed, such inhibitors improve the potency of ?-lactams in vitro against inducible AmpC ?-lactamase-producing bacteria. We describe the key steps of cell-wall remodeling and recycling, the regulation of resistance mechanisms by cell-wall recycling, and recent advances toward the discovery of cell-wall recycling inhibitors.

Johnson, Jarrod W.; Fisher, Jed F.; Mobashery, Shahriar

2012-01-01

347

Recycling Study Guide [Resource Packet].  

ERIC Educational Resources Information Center

This resource packet contains six documents developed by the Wisconsin Department of Natural Resources in order to help teachers infuse the environmental education topics of recycling and solid waste into social studies, art, English, health, mathematics, science, and environmental education classes. "Recycling Study Guide" contains 19 activities…

Wisconsin State Dept. of Natural Resources, Madison.

348

The Dynamic Earth: Recycling Naturally!  

ERIC Educational Resources Information Center

This article begins with a thought-provoking question: What do you think of when you hear the term "recycle?" Many think about paper, glass, aluminum cans, landfills, and reducing waste by reusing some of these materials. How many of us ever consider the way the systems of Earth dynamically recycle its materials? In the following…

Goldston, M. Jenice; Allison, Elizabeth; Fowler, Lisa; Glaze, Amanda

2013-01-01

349

Tomato Cleaning and Water Recycle.  

National Technical Information Service (NTIS)

A full-scale dump tank water recycle system was developed and demonstrated. A false bottom-ejector transport system removed soil from the water. Clarified water was either recycled back to the dump tank or discharged to the sewer. A vacuum belt was develo...

W. W. Rose

1982-01-01

350

Recycling Solid Waste in Chattanooga  

ERIC Educational Resources Information Center

Students undertook a group project in collaboration with city officials to study garbage types in the community and possibilities of recycling solid wastes. Data collected from various sources revealed that public attitude was favorable for recycling efforts and that it was feasible economically. (PS)

Vredeveld, Ruth; Martin, Robin

1973-01-01

351

Climate Kids: Recycling Program Educator  

NSDL National Science Digital Library

Using her countywide program as an example, a recycling educator offers incentives for recycling by providing data on energy savings and explaining how her county in Michigan supports the program. The Climate Kids website is a NASA education resource featuring articles, videos, images and games focused on the science of climate change.

352

Information Sources on Rural Recycling.  

ERIC Educational Resources Information Center

Provides resources for rural recycling operations with the principle aim of assisting rural government officials, planners, residents, and educators to encourage recycling as an integral part of an individual's or community's solid waste management plan. Sources range from bibliographies, directories, and government documents to case studies. (49…

Notess, Greg; Kuske, Jodee

1992-01-01

353

TOMATO CLEANING AND WATER RECYCLE  

EPA Science Inventory

A full-scale dump tank water recycle system was developed and demonstrated. A false bottom-ejector transport system removed soil from the water. Clarified water was either recycled back to the dump tank or discharged to the sewer. A vacuum belt was developed for dewatering the mu...

354

Performance of additives in reducing ammonia emissions from cow slurry.  

National Technical Information Service (NTIS)

Ammonia emissions contribute substantially to environmental pollution and cause severe acidification. In Sweden, 20-25% of the total ammonia emission derives from manure in animal buildings. One technique to decrease ammonia emissions from animal building...

M. Andersson

1994-01-01

355

Electro Decomposition of Ammonia into Hydrogen for Fuel Cell Use.  

National Technical Information Service (NTIS)

This work was undertaken to create an efficient process for electrolyzing ammonia, by clarifying the electrolytic decomposition path-ways of ammonia and urea. This project demonstrated the feasibility of using ammonia and urea electrolysis technologies to...

C. A. Feickert G. G. Bottle

2012-01-01

356

pp v-viii Percolation transport in random flows with weak dissipation effects  

NASA Astrophysics Data System (ADS)

In the present paper, we consider the influence of weak dissipative effects on the passive scalar behavior in the framework of continuum percolation approach. The renormalization method of a small parameter in continuum percolation models is reviewed. It is shown that there is a characteristic velocity scale, which corresponds to the dissipative process. The modification of the renormalization condition of the small percolation parameter is suggested in accordance with additional external influences superimposed on the system. In the framework of mean-field arguments, the balance of correlation scales is considered. This gives the characteristic time that corresponds to the percolation regime. The expression for the effective coefficient of diffusion is obtained.

Bakunin, O. G.

2005-01-01

357

Nitric oxide: interaction with the ammonia monooxygenase and regulation of metabolic activities in ammonia oxidizers.  

PubMed

The biological nitrogen cycle is a complex interplay of many microorganisms. In the past, oxidation of the inorganic nitrogen compound ammonia by the ammonia oxidizing bacteria was thought to be restricted to oxic environments, and the metabolic flexibility of these organisms seemed to be limited. The discovery of an anaerobic metabolism in the late 1990s showed that these assumptions are no longer valid. NO and NO(2) are essential intermediates in ammonia oxidation. Both gases have wide-ranging regulatory effects on ammonia oxidation, denitrification, and biofilm formation of the ammonia oxidizing bacteria. PMID:18423214

Schmidt, Ingo

2008-01-01

358

Magnetically separable and recyclable urchin-like Co-P hollow nanocomposites for catalytic hydrogen generation  

NASA Astrophysics Data System (ADS)

One-pot well-controlled synthetic strategy was developed to achieve urchin-like Co-P hollow nanocomposites with tailorable magnetic properties which enable them to perform as magnetically recyclable nanocatalysts in a “quasi-homogeneous” system for the catalytic hydrogen generation via hydrolysis of Ammonia-Borane (AB). The key point of this strategy was that ferromagnetic Co nanoparticles (NPs) were embedded into paramagnetic Co2P matrix to form magnetic nanocomposites. The as-prepared Co-P NPs showed appreciable catalytic activity, recyclability and durability in hydrolysis of AB. Moreover, the chemical regeneration of AB from the “hydrolyzate” may also benefit from these magnetically recyclable catalysts. We further highlighted the excellent high-temperature resistance of Co-P NPs by calcining them at 300 °C and 600 °C. Our research may facilitate the practical application of AB as a sustainable hydrogen storage material for hydrogen-based energy.

Guo, Huizhang; Liu, Xiang; Hou, Yuhui; Xie, QingShui; Wang, Laisen; Geng, Hao; Peng, Dong-Liang

359

Ammonia-oxidizing archaea involved in nitrogen removal  

Microsoft Academic Search

Ammonia oxidation is critical to global nitrogen cycling and is often thought to be driven only by ammonia-oxidizing bacteria. The recent finding of new ammonia-oxidizing organisms belonging to the archaeal domain challenges this perception. Two major microbial groups are now believed to be involved in ammonia oxidation: chemolithotrophic ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Candidatus “Nitrosopumilus maritimus”, the first

Jia You; Atreyee Das; Elizabeth M. Dolan; Zhiqiang Hu

2009-01-01

360

Novel surface mount LED ammonia sensors  

Microsoft Academic Search

Low-cost colorimetric ammonia gas sensors have been developed using a pair of surface mount light emitting diodes (LEDs), ammonia specific chemochromic reagent and a simple PIC microcontroller circuit. The key feature of this sensor is the use of an LED, rather than a photodiode, for light detection. The use of surface mount diodes means a significant reduction in the final

Roderick L. Shepherd; William S. Yerazunis; King Tong Lau; Dermot Diamond

2004-01-01

361

Fabrication of Functional Nanofibrous Ammonia Sensor  

Microsoft Academic Search

A nanofibrous sensor for ammonia gas is fabricated by electrospinning the composite of poly(diphenylamine) (PDPA) with poly(methyl methacrylate) (PMMA) onto the patterned interdigit electrode. The composite electrospun membrane shows interconnected fibrous morphology. Functional groups in PDPA and the high active surface area of the fibrous membrane make the device detect a lower concentration of ammonia with a good reproducibility. The

Kalayil Manian Manesh; Anantha Iyengar Gopalan; Kwang-Pill Lee; Padmanabhan Santhosh; Kap-Duk Song; Duk-Dong Lee

2007-01-01

362

METHODOLOGY AND INSTRUMENTATION TO MEASURE GASEOUS AMMONIA  

EPA Science Inventory

Methodology for the time integrated collection and analysis of atmospheric ammonia was developed. Ammonia is primarily measured because it can react with SOx to produce ammonium sulfate. Since SOx is one of the principle air pollutants, it is important to determine its atmospheri...

363

Photoinactivation of Ammonia Oxidation in Nitrosomonas  

PubMed Central

Photoinactivation of ammonia oxidation in cells of Nitrosomonas was shown to follow first-order kinetics with a rate constant proportional to incident light intensity. The action spectrum for photoinactivation consisted of a broad peak in the ultraviolet range, where both hydroxylamine and ammonia oxidation were affected, and a shoulder at approximately 410 nm where only ammonia oxidation was affected. In photoinactivated cells, hydroxylamine but not ammonia was oxidized to nitrite and hydroxylamine but not ammonia caused reduction of cytochromes in vivo. The amount per cell of the following constituents was not measurably altered by photoinactivation: cytochromes b, c, a, and P460; ubiquinone; phospholipid; free amino acids; hydroxylamine-dependent nitrite synthetase; nitrite reductase; p-phenylenediamine oxidase; and cytochrome c oxidase. Malonaldehyde or lipid peroxides were not detected in photoinactivated cells. Photoinactivation was prevented (i) under anaerobic conditions, (ii) in the presence of methanol, allylthiourea, thiosemicarbazide, hydroxylamine, ethylxanthate, or CO at concentrations wich caused 100% inhibition of ammonia oxidation, and (iii) at concentrations of ammonia or hydroxylamine which gave a rapid rate of nitrite production. Recovery of ammonia oxidation activity in 90% inactivated cells took place in 6 h, required an energy and/or nitrogen source, and was inhibited by 400 ?g of chloramphenicol per ml.

Hooper, Alan B.; Terry, Kathleen R.

1974-01-01

364

Regeneration of ammonia borane from polyborazylene  

DOEpatents

Method of producing ammonia borane, comprising providing a reagent comprising a dehydrogenated material in a suitable solvent; and combining the reagent with a reducing agent comprising hydrazine, a hydrazine derivative, or combinations thereof, in a reaction which produces a mixture comprising ammonia borane.

Sutton, Andrew; Gordon, John C; Ott, Kevin C; Burrell, Anthony K

2013-02-05

365

Jupiter's ammonia clouds—localized or ubiquitous?  

Microsoft Academic Search

From an analysis of the Galileo Near Infrared Imaging Spectrometer (NIMS) data, Baines et al. (Icarus 159 (2002) 74) have reported that spectrally identifiable ammonia clouds (SIACs) cover less than 1% of Jupiter. Localized ammonia clouds have been identified also in the Cassini Composite Infrared Spectrometer (CIRS) observations (Planet. Space Sci. 52 (2004a) 385). Yet, ground-based, satellite and spacecraft observations

S. K. Atreya; A. S. Wong; K. H. Baines; M. H. Wong; T. C. Owen

2005-01-01

366

Recycle of waste paper  

SciTech Connect

One of the Oak Ridge Y-12 Plant's long range goals is to reduce the amount of waste from the plant. The large amount of waste paper generated by the plant is currently buried in the state permitted landfill. Methods of recycling cardboard and paper which comply with all security requirements, health, safety, and environmental regulations of the Y-12 Plant are sought to conserve the landfill. A process to compact paper into a form which may be used as fuel and fed into the existing steam plant has been developed. A water-resistant briquette has been made from waste paper, a binder, and coal. Laboratory and pilot scale briquetting and pulverizing tests have been completed. These briquettes have physical properties similar to those of coal. 12 tabs.

Hackett, G.D.; Harris, G.E.

1988-01-01

367

Percolation simulation of laser-guided electrical discharges.  

PubMed

A three-dimensional simulation of laser-guided discharges based on percolation is presented. The model includes both local growth of a streamer due to the enhanced electric field at the streamer's tip and propagation of a leader by remote ionization such as that caused by runaway electrons. The stochastic behavior of the discharge through a preformed plasma channel is reproduced by the calculation, which shows complex path with detouring and bifurcation. The probability of guiding is investigated with respect to the ionized, conductive fraction along the channel. PMID:20868054

Sasaki, Akira; Kishimoto, Yasuaki; Takahashi, Eiichi; Kato, Susumu; Fujii, Takashi; Kanazawa, Seiji

2010-08-13

368

Percolative phenomena and electrorheological structures in reverse micelles  

NASA Astrophysics Data System (ADS)

Structural relaxations in AOT (sodium bis(2-ethylhexyl) sulphosuccinate) and lecithin reverse micelles are investigated by means of dielectric relaxation and conductivity measurements. The different behaviours exhibited by the two systems are interpreted in terms of the different kinds of interaction between the water and the surfactant molecules. In the case of lecithin, the application of an external electric field induces the establishing of some electrorheological structure. The temperature dependence of the observed electrorheological effects agrees with the hypothesis of a structural arrangement consisting in a percolated network of branched cylindrical micelles. The experimental results are compared with other literature data and discussed within the framework of the current theories.

Aliotta, F.

2002-03-01

369

Evidence of percolative phenomena in a lecithin-based gel  

NASA Astrophysics Data System (ADS)

The structure of the gel-phase, observed in a number of lecithin-in-oil microemulsions after addition of water, is the topic of a controversy actually taking place in the literature. In this paper, we will show how the dynamical properties of water confined in the inner core of the micelles, as investigated by QENS and INS, turn out to be inconsistent with the usually proposed model of entangled (not interconnected) polymer-like micelles. A percolated structure of branched cylindrical aggregates could agree with the presented data.

Aliotta, F.; Vasi, C.; Lechner, R. E.; Ruffle, B.

2000-03-01

370

From damage percolation to crack nucleation through finite size criticality.  

PubMed

We present a unified theory of fracture in disordered brittle media that reconciles apparently conflicting results reported in the literature. Our renormalization group based approach yields a phase diagram in which the percolation fixed point, expected for infinite disorder, is unstable for finite disorder and flows to a zero-disorder nucleation-type fixed point, thus showing that fracture has a mixed first order and continuous character. In a region of intermediate disorder and finite system sizes, we predict a crossover with mean-field avalanche scaling. We discuss intriguing connections to other phenomena where critical scaling is only observed in finite size systems and disappears in the thermodynamic limit. PMID:23683218

Shekhawat, Ashivni; Zapperi, Stefano; Sethna, James P

2013-05-01

371

Second harmonic generation enhancement at the percolation threshold  

NASA Astrophysics Data System (ADS)

We systematically investigate the second harmonic generated (SHG) signal created by metallic semi-continuous thin films as a function of the effective layer thickness for a large number of samples. The control of the film thickness allows us to precisely map the region around the percolation threshold. We obtain a sharp and intense SHG peak at the critical thickness where the near static permittivity diverges. This happens in the regime of almost touching particles while the thin film does not behave as a metal yet. This large SHG signal is obtained with samples fabricated using a thin film deposition technique that is easily wafer scalable.

De Zuani, Stefano; Peterseim, Tobias; Berrier, Audrey; Gompf, Bruno; Dressel, Martin

2014-06-01

372

Emergent Spin Excitations in a Bethe Lattice at Percolation  

NASA Astrophysics Data System (ADS)

We study the spin-1/2 quantum Heisenberg antiferromagnet on a Bethe lattice diluted to the percolation threshold. Dilution creates areas of even or odd sublattice imbalance resulting in “dangling spins” [L. Wang and A. W. Sandvik, Phys. Rev. Lett. 97, 117204 (2006); Phys. Rev. B 81, 054417 (2010)]. These collectively act as “emergent” spin-1/2 degrees of freedom and are responsible for the creation of a set of low-lying “quasidegenerate states.” Using density matrix renormalization group calculations, we detect the presence and location of these emergent spins. We find an effective Hamiltonian of these emergent spins, with Heisenberg interactions that decay exponentially with the distance between them.

Changlani, Hitesh J.; Ghosh, Shivam; Pujari, Sumiran; Henley, Christopher L.

2013-10-01

373

Fixed-Energy Sandpiles Belong Generically to Directed Percolation  

NASA Astrophysics Data System (ADS)

Fixed-energy sandpiles with stochastic update rules are known to exhibit a nonequilibrium phase transition from an active phase into infinitely many absorbing states. Examples include the conserved Manna model, the conserved lattice gas, and the conserved threshold transfer process. It is believed that the transitions in these models belong to an autonomous universality class of nonequilibrium phase transitions, the so-called Manna class. Contrarily, the present numerical study of selected (1+1)-dimensional models in this class suggests that their critical behavior converges to directed percolation after very long time, questioning the existence of an independent Manna class.

Basu, Mahashweta; Basu, Urna; Bondyopadhyay, Sourish; Mohanty, P. K.; Hinrichsen, Haye

2012-07-01

374

Corner contribution to percolation cluster numbers in three dimensions  

NASA Astrophysics Data System (ADS)

In three-dimensional critical percolation we study numerically the number of clusters N? which intersect a given subset of bonds ?. If ? represents the interface between a subsystem and the environment, then N? is related to the entanglement entropy of the critical diluted quantum Ising model. Due to corners in ? there are singular corrections to N?, which scale as b?lnL?, with L? being the linear size of ? and the prefactor b? is found to be universal. This result indicates that logarithmic finite-size corrections exist in the free energy of three-dimensional critical systems.

Kovács, István A.; Iglói, Ferenc

2014-05-01

375

Crosslinked biopolymers: Experimental evidence for scalar percolation theory  

NASA Astrophysics Data System (ADS)

Rheological measurements have been performed on pectin biopolymers close to the sol-gel transition. From these measurements scaling exponents were determined independently for the viscosity, s=0.82(5), for the elastic modulus, t=1.93(8), for the frequency-dependent modulus, ?=0.71(2), and for the relaxation times below and above the transition, ?z=2.67(12) and ?z'=2.65(9). The exponents satisfy the scaling relations predicted by the theory and their numerical values agree with those from scalar elasticity percolation. Universal scaling functions were constructed from the data for the complex modulus and the dynamic viscosity.

Axelos, M. A. V.; Kolb, M.

1990-03-01

376

Performance Testing of the Vapor Phase Catalytic Ammonia Removal Engineering Development Unit  

NASA Technical Reports Server (NTRS)

This paper describes the results of performance testing of the Vapor Phase Catalytic Ammonia Removal (VPCAR) technology. The VPCAR technology is currently being developed by NASA as a Mars transit vehicle water recycling system. NASA has recently completed-a grant-to develop a next generation VPCAR system. This grant concluded with the shipment of the final deliverable to NASA on 8/31/03. This paper presents the results of mass, power, volume, and acoustic measurements for the delivered system. Product water purity analysis for a Mars transit mission and a simulated planetary base wastewater ersatz are also provided.

Flynn, Michael; Tleimat, Maher; Nalette, Tim; Quinn, Gregory

2005-01-01

377

Open-loop recycling: A LCA case study of PET bottle-to-fibre recycling  

Microsoft Academic Search

This study assesses the environmental impact of polyethylene terephthalate (PET) bottle-to-fibre recycling using the methodology of life-cycle assessment (LCA). Four recycling cases, including mechanical recycling, semi-mechanical recycling, back-to-oligomer recycling and back-to-monomer recycling were analysed. Three allocation methods are applied for open-loop recycling, i.e. the “cut-off” approach, the “waste valuation” approach and the “system expansion” approach. Nine environmental impact indicators were

Li Shen; Ernst Worrell; Martin K. Patel

2010-01-01

378

Plastics recycling: challenges and opportunities  

PubMed Central

Plastics are inexpensive, lightweight and durable materials, which can readily be moulded into a variety of products that find use in a wide range of applications. As a consequence, the production of plastics has increased markedly over the last 60 years. However, current levels of their usage and disposal generate several environmental problems. Around 4 per cent of world oil and gas production, a non-renewable resource, is used as feedstock for plastics and a further 3–4% is expended to provide energy for their manufacture. A major portion of plastic produced each year is used to make disposable items of packaging or other short-lived products that are discarded within a year of manufacture. These two observations alone indicate that our current use of plastics is not sustainable. In addition, because of the durability of the polymers involved, substantial quantities of discarded end-of-life plastics are accumulating as debris in landfills and in natural habitats worldwide. Recycling is one of the most important actions currently available to reduce these impacts and represents one of the most dynamic areas in the plastics industry today. Recycling provides opportunities to reduce oil usage, carbon dioxide emissions and the quantities of waste requiring disposal. Here, we briefly set recycling into context against other waste-reduction strategies, namely reduction in material use through downgauging or product reuse, the use of alternative biodegradable materials and energy recovery as fuel. While plastics have been recycled since the 1970s, the quantities that are recycled vary geographically, according to plastic type and application. Recycling of packaging materials has seen rapid expansion over the last decades in a number of countries. Advances in technologies and systems for the collection, sorting and reprocessing of recyclable plastics are creating new opportunities for recycling, and with the combined actions of the public, industry and governments it may be possible to divert the majority of plastic waste from landfills to recycling over the next decades.

Hopewell, Jefferson; Dvorak, Robert; Kosior, Edward

2009-01-01

379

Coal liquefaction with preasphaltene recycle  

DOEpatents

A coal liquefaction system is disclosed with a novel preasphaltene recycle from a supercritical extraction unit to the slurry mix tank wherein the recycle stream contains at least 90% preasphaltenes (benzene insoluble, pyridine soluble organics) with other residual materials such as unconverted coal and ash. This subject process results in the production of asphaltene materials which can be subjected to hydrotreating to acquire a substitute for No. 6 fuel oil. The preasphaltene-predominant recycle reduces the hydrogen consumption for a process where asphaltene material is being sought.

Weimer, Robert F. (Allentown, PA); Miller, Robert N. (Allentown, PA)

1986-01-01

380

Recycling and Life Cycle Issues  

SciTech Connect

This chapter addresses recycling and life cycle considerations related to the growing use of lightweight materials in vehicles. The chapter first addresses the benefit of a life cycle perspective in materials choice, and the role that recycling plays in reducing energy inputs and environmental impacts in a vehicle s life cycle. Some limitations of life cycle analysis and results of several vehicle- and fleet-level assessments are drawn from published studies. With emphasis on lightweight materials such as aluminum, magnesium, and polymer composites, the status of the existing recycling infrastructure and technological challenges being faced by the industry also are discussed.

Das, Sujit [ORNL

2010-01-01

381

Clustering of asbestos fibres in cell damage: A percolational perspective  

NASA Astrophysics Data System (ADS)

In vitro researches on rat cells exposed to several types of thin asbestos fibres show a saturation in cytotoxicity as one increases the fibre concentration n on the cell surface. For given average fibre lengths, the saturation occurs at values that are 2-3 times the critical concentration nc for a percolative arrangement of randomly thrown sticks on a surface. Measurements of the threshold for genotoxic damage give concentrations that are about 0.1nc. One expects that, somewhere between these concentrations, large scale "critical fluctuations" will be observed in the data. These fluctuations are indeed seen in chrysotile treated rat pleural mesothelial cells, exhibiting DNA damage and chromosomal-number aberrations. We hypothesize that at such concentrations that fibre-clustering occurs, the fibres lock together and are hindered from traversing the cell membranes and internalizing. Some damage processes are thereby impeded. The kinetics of internalization is worked out with models involving continuum percolation. Pieces of evidence from in vivo results that support the theory are noted.

Englman, Robert; Jaurand, Marie-Claude

1997-03-01

382

Ultralow percolation threshold in aerogel and cryogel templated composites.  

PubMed

We demonstrate a novel concept for preparing percolating composites with ultralow filler content by utilizing nanofiller-loaded aerogel and cryogels as a conductive template. This concept is investigated for several porous systems, including resorcinol-formaldehyde (RF), silica, and polyacrylamide (PAM) gels, and both graphene and carbon nanotubes are utilized as nanofiller. In each case, a stable, aqueous nanofiller dispersion is mixed with a sol-gel precursor and polymerized to form a hydrogel, which can then be converted to an aerogel by critical point drying or cryogel by freeze-drying. Epoxy resin is infused into the pores of the gels by capillary action without disrupting the monolithic structure. We show that conductive graphene/epoxy composites are formed with a very low graphene loading; a percolation threshold as low as 0.012 vol % is obtained for graphene-RF cryogel/epoxy composite. This is the lowest reported threshold of any graphene-based nanocomposites. Similar values are achieved in other aerogel and nanofiller systems, which demonstrates the versatility of this method. PMID:23927050

Irin, Fahmida; Das, Sriya; Atore, Francis O; Green, Micah J

2013-09-10

383

Percolation phenomenon in ternary microemulsions: The effect of pressure  

NASA Astrophysics Data System (ADS)

The electrical conductivity ? and dynamic viscosity ? of water-based water-AOT-undecane [AOT:sodium bis(2-ethylhexyl) sulfosuccinate] microemulsions and waterless glycerol-AOT-isooctane microemulsions were studied as a function of volume fraction ? in dispersed matter (water plus AOT or glycerol plus AOT) and pressure up to 1000 bar. The realm of existence of the single-phase zone was also determined versus pressure P. The curves ?(P) and ?(P) at constant ? and temperature T, and the curves ?(?) and ?(?) at constant P and T were analyzed within the framework of percolation theory. For water-based microemulsions the percolation threshold ?c decreases when P increases, corresponding to an increase in interactions. For waterless microemulsions ?c varies very little. The scaling exponents are ~=2 above the threshold and ~=-1.2 below, whatever the pressure, the system, and the property studied (values which have already between obtained at 1 bar). This corresponds to the fact that these systems belong to the same class of universality.

Boned, C.; Saidi, Z.; Xans, P.; Peyrelasse, J.

1994-06-01

384

Role of local and global geometry in entanglement percolation  

NASA Astrophysics Data System (ADS)

We prove that enhanced entanglement percolation via lattice transformation is possible even if the new lattice is more poorly connected in that (i) the coordination number (a local property) decreases, or (ii) the classical percolation threshold (a global property) increases. In searching for protocols to transport entanglement across a network, it seems reasonable to try transformations that increase connectivity. In fact, all examples that we are aware of violate both conditions (i) and (ii). One might therefore conjecture that all good transformations must violate them. Here we introduce a method, partial entanglement swapping, and use it to construct a counterexample that satisfies conditions (i) and (ii). The example lowers the threshold, relative to all known protocols, of the amount of initial entanglement required for deterministic long-range entanglement. This result shows that a transformation may not be rejected on the basis of satisfying conditions (i) or (ii). Both the result and the method constitute steps toward answering basic questions, such as whether there is a minimum amount of local entanglement required to achieve long-range entanglement.

Lapeyre, Gerald John

2014-01-01

385

Epoxy resin/carbon black composites below the percolation threshold.  

PubMed

A set of epoxy resin composites filled with 0.25-2.0 wt.% of commercially available ENSACO carbon black (CB) of high and low surface area (CBH and CBL respectively) has been produced. The results of broadband dielectric spectroscopy of manufactured CB/epoxy below the percolation threshold in broad temperature (200 K to 450 K) and frequency (20 Hz to 1 MHz) ranges are reported. The dielectric properties of composites below the percolation threshold are mostly determined by alpha relaxation in pure polymer matrix. The glass transition temperature for CB/epoxy decreases in comparison with neat epoxy resin due to the extra free volume at the polymer-filler interface. At room temperature, the dielectric permittivity is higher for epoxy loaded with CBH additives. In contrast, at high temperature, the electrical conductivity was found to be higher for composites with CBL embedded. The established influence of the CB surface area on the broadband dielectric characteristics can be exploited for the production of effective low-cost antistatic paints and coatings working at different temperatures. PMID:23882775

Macutkevic, J; Kuzhir, P; Paddubskaya, A; Maksimenko, S; Banys, J; Celzard, A; Fierro, V; Stefanutti, E; Cataldo, A; Micciulla, F; Bellucci, S

2013-08-01

386

Percolation theory and connectivity of multiscale porous media  

NASA Astrophysics Data System (ADS)

It is well known that flow and transport properties in porous media vary as non-linear functions of the porosity and that the macroscopic conductivity of a soil sample is stronly dependent on the connectivity of the pore network observed at a microscopic scale. Connectivity is a key parameter which is still difficult to quantify. We present first a review on the basic concepts of percolation theory and on their application to the standard modelling of critical transitions in the connectivity of pore or fracture subnetworks. Then we show how these concepts have to be revisited when the pore network is non longer randomly distributed, and namely when the medium is structured on multiple embedded organisation scales. We finally present some novel research results obtained on multiscale fractal soil models as regards the probability for pore or solid networks to percolate as a function of the type of geometrical organization : in particular we highligt the possibility of high porosity structures supporting impaired flow and transport. The presentation of several computer simulations illustrates the theoretical concepts. In turn, the theoretical formalism will serve as a guide for assessing the asymptotic behavior of multiscale simulated networks, in the growing research field of network modelling applied to complex natural systems.

Perrier, E.; Bird, N.

2009-04-01

387

Experimental and computational investigation of percolation in complex polymer nanocomposites  

NASA Astrophysics Data System (ADS)

The continuing development of polymer nanocomposites has led to increasingly complex morphology, such as the mats of composite nanofibers formed from electrospinning. The formation of particle networks within the composite volume that leads to enhanced properties, such as electrical conductivity, may be influenced by this complex sample geometry. In this work, experimental and computational efforts are utilized to understand and predict the percolation threshold (critical volume fraction) for two cases: single ultra-high aspect ratio fibers (where fiber diameter can be similar to the particle dimensions) and these same fibers arranged in a random mat with up to 80% porosity. 2D and 3D Monte Carlo simulations, modeled on the actual parameters of our experimental system [1], are utilized and the results are compared with our experimental findings. In particular, confinement to fibers increases the percolation threshold; however the multi-fiber pathways available in mats partially reduce this constraint [2]. [1] S.S. Ojha, D.R. Stevens, K. Stano, T. Hoffman, L.I. Clarke, R.E. Gorga, Macromolecules 41, 2509 (2008). [2] D.R. Stevens, L.N. Downen, L.I. Clarke, Phys. Rev. B in press (2008).

Stevens, Derrick; Downen, Lori; Gorga, Russell; Clarke, Laura

2009-03-01

388

From Earth to Space: Application of Biological Treatment for the Removal of Ammonia from Water  

NASA Technical Reports Server (NTRS)

Managing ammonia is often a challenge in both drinking water and wastewater treatment facilities. Ammonia is unregulated in drinking water, but its presence may result in numerous water quality issues in the distribution system such as loss of residual disinfectant, nitrification, and corrosion. Ammonia concentrations need to be managed in wastewater effluent to sustain the health of receiving water bodies. Biological treatment involves the microbiological oxidation of ammonia to nitrate through a two-step process. While nitrification is common in the environment, and nitrifying bacteria can grow rapidly on filtration media, appropriate conditions, such as the presence of dissolved oxygen and required nutrients, need to be established. This presentation will highlight results from two ongoing research programs - one at NASA's Johnson Space Center, and the other at a drinking water facility in California. Both programs are designed to demonstrate nitrification through biological treatment. The objective of NASA's research is to be able to recycle wastewater to potable water for spaceflight missions. To this end, a biological water processor (BWP) has been integrated with a forward osmosis secondary treatment system (FOST). Bacteria mineralize organic carbon to carbon dioxide as well as ammonia-nitrogen present in the wastewater to nitrogen gas, through a combination of nitrification and denitrification. The effluent from the BWP system is low in organic contaminants, but high in total dissolved solids. The FOST system, integrated downstream of the BWP, removes dissolved solids through a combination of concentration-driven forward osmosis and pressure driven reverse osmosis. The integrated system testing planned for this year is expected to produce water that requires only a polishing step to meet potable water requirements for spaceflight. The pilot study in California is being conducted on Golden State Water Company's Yukon wells that have hydrogen sulfide odor, color, total organic carbon, bromide, iron and manganese in addition to ammonia. A treatment evaluation, conducted in 2011, recommended the testing of biological oxidation filtration for the removal of ammonia and production of biologically stable water. An 8-month pilot testing program was conducted to develop and optimize key design and operational variables. Steadystate operational data was collected to demonstrate long-term performance and inform California Department of Public Health permitting of the full-scale process. As ammonia continues to present challenges to water and wastewater systems, innovative strategies such as biological treatment can be applied to successfully manage it. This presentation will discuss application of cutting-age research being conducted by NASA that will bridge existing information gaps, and benefit municipal utilities.

Pickering, Karen; Adam, Niklas; White, Dawn; Ghosh, Amlan; Seidel, Chad

2014-01-01

389

From Earth to Space: Application of Biological Treatment for the Removal of Ammonia from Water  

NASA Technical Reports Server (NTRS)

Managing ammonia is often a challenge in both drinking water and wastewater treatment facilities. Ammonia is unregulated in drinking water, but its presence may result in numerous water quality issues in the distribution system such as loss of residual disinfectant, nitrification, and corrosion. Ammonia concentrations need to be managed in wastewater effluent to sustain the health of receiving water bodies. Biological treatment involves the microbiological oxidation of ammonia to nitrate through a two-step process. While nitrification is common in the environment, and nitrifying bacteria can grow rapidly on filtration media, appropriate conditions, such as the presence of dissolved oxygen and required nutrients, need to be established. This presentation will highlight results from two ongoing research programs - one at NASA's Johnson Space Center, and the other at a drinking water facility in California. Both programs are designed to demonstrate nitrification through biological treatment. The objective of NASA's research is to be able to recycle wastewater to potable water for spaceflight mission. To this end, a biological water processor (BWP) has been integrated with a forward osmosis secondary treatment system (FOST). Bacteria mineralize organic carbon to carbon dioxide as well as ammonia-nitrogen present in the wastewater to nitrogen gas, through a combination of nitrification and denitrification. The effluent from the BWP system is low in organic contaminants, but high in total dissolved solids. The FOST system, integrated downstream of the BWP, removes dissolved solids through a combination of concentration-driven forward osmosis and pressure driven reverse osmosis. The integrated system testing planned for this year is expected to produce water that requires only a polishing step to meet potable water requirements for spaceflight. The pilot study in California is being conducted on Golden State Water Company's Yukon wellsthat have hydrogen sulfide odor, color, total organic carbon, bromide, iron and manganese in addition to ammonia. A treatment evaluation, conducted in 2011, recommended the testing of biological oxidation filtration for the removal of ammonia and production of biologically stable water. A 8-month pilot testing program was conducted to develop and optimize key design and operational variables. Steadystate operational data was collected to demonstrate long-term performance and inform California Department of Public Health permitting of the full-scale process. As ammonia continues to present challenges to water and wastewater systems, innovative strategies such as biological treatment can be applied to successfully manage it. This presentation will discuss application of cutting-age research being conducted by NASA that will bridge existing information gaps, and benefit municipal utilities.

Ghosh, Amlan; Seidel, Chad; Adam, Niklas; Pickering, Karen; White, Dawn

2014-01-01

390

Percolation path and dielectric-breakdown-induced-epitaxy evolution during ultrathin gate dielectric breakdown transient  

Microsoft Academic Search

A physical model has been developed which complies with the experimental observation on the failure mechanism of ultrathin gate oxide breakdown during constant voltage stress. Dynamic equilibrium needs to be established between the percolation conductive path and the dielectric breakdown induced epitaxy (DBIE) formation during gate dielectric breakdown transient. The model is capable of linking the percolation model, soft breakdown,

Chih Hang Tung; Kin Leong Pey; Lei Jun Tang; M. K. Radhakrishnan; Wen He Lin; Felix Palumbo; Salvatore Lombardo

2003-01-01

391

Effect of particle size ratio on the conducting percolation threshold of granular conductive insulating composites  

Microsoft Academic Search

In this paper, we apply Monte Carlo simulation to investigate the conductive percolation threshold of granular composite of conductive and insulating powders with amorphous structure. We focus on the effect of insulating to conductive particle size ratio lgr = di\\/dc on the conducting percolation threshold pc (the volume fraction of the conductive powder). Simulation results show that, for lgr =

Da He; N. N. Ekere

2004-01-01

392

Ammonia synthesis using magnetic induction method (MIM)  

NASA Astrophysics Data System (ADS)

The most challenging issues for ammonia synthesis is to get the high yield. New approach of ammonia synthesis by using Magnetic Induction Method (MIM) and the Helmholtz Coils has been proposed. The ammonia detection was done by using Kjeldahl Method and FTIR. The system was designed by using Autocad software. The magnetic field of MIM was vary from 100mT-200mT and the magnetic field for the Helmholtz coils was 14mT. The FTIR result shows that ammonia has been successfully formed at stretching peaks 1097,1119,1162,1236, 1377, and 1464 cm-1. UV-VIS result shows the ammonia bond at 195nm of wavelength. The ammonia yield was increase to 244.72?mole/g.h by using the MIM and six pairs of Helmholtz coils. Therefore this new method will be a new promising method to achieve the high yield ammonia at ambient condition (at 25?C and 1atm), under the Magnetic Induction Method (MIM).

Puspitasari, P.; Razak, J. Abd; Yahya, N.

2012-09-01

393

INFRARED SPECTRA OF AMMONIA-WATER ICES  

SciTech Connect

We conducted a systematic study of the near-IR and mid-IR spectra of ammonia-water ices at various NH{sub 3}/H{sub 2}O ratios. The differences between the spectra of amorphous and crystalline ammonia-water ices were also investigated. The 2.0 {mu}m ammonia band central wavelength is a function of the ammonia/water ratio. It shifts from 2.006 {+-} 0.003 {mu}m (4985 {+-} 5 cm{sup -1}) to 1.993 {+-} 0.003 {mu}m (5018 {+-} 5 cm{sup -1}) as the percentage of ammonia decreases from 100% to 1%. The 2.2 {mu}m ammonia band center shifts from 2.229 {+-} 0.003 {mu}m (4486 {+-} 5 cm{sup -1}) to 2.208 {+-} 0.003 {mu}m (4528 {+-} 5 cm{sup -1}) over the same range. Temperature-dependent shifts of those bands are below the uncertainty of the measurement, and therefore are not detectable. These results are important for comparison with astronomical observations as well as for estimating the concentration of ammonia in outer solar system ices.

Zheng Weijun; Jewitt, David [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Kaiser, Ralf I. [Department of Chemistry, University of Hawaii, Honolulu, HI 96822 (United States)], E-mail: jewitt@ifa.hawaii.edu, E-mail: ralfk@hawaii.edu, E-mail: zhengwj@iccas.ac.cn

2009-03-15

394

Low-cost anodes for ammonia electrooxidation  

NASA Astrophysics Data System (ADS)

This research focused on the development of low-cost electrodes for the electrochemical oxidation of ammonia to nitrogen, a reaction that has possible applications in hydrogen generation, direct ammonia fuel cells, water treatment, and sensors. Statistical design of experiments was used to help develop an efficient and scalable process for electrodeposition of platinum with a specific electrochemical surface area of over 25 m2 /g. Catalyst surface area and activity were evaluated using cyclic voltammetry, and the material microstructure and morphology were investigated using x-ray diffraction and scanning electron microscopy. The synthesized electrodes were found to be active toward the ammonia electrooxidation reaction, particularly when supporting electrolyte was added. However, supporting electrolyte was not required in order to oxidize the ammonia. As proof of concept, a homemade direct ammonia fuel cell employing a commercial anion exchange membrane was tested at room temperature with gravity-fed fuel and without supporting electrolyte. At room temperature, with passive reactant supply and using dissolved oxygen at the cathode, the cell produced about one quarter the power of a direct methanol fuel cell that used active transport of humidified oxygen and preheated (50 °C) methanol. With continued development of the membrane, cathode and membrane electrode assembly, the passive direct ammonia fuel cell using anion exchange membrane could have performance similar to the equivalent direct methanol fuel cell, and it could benefit from many advantages of ammonia over methanol such as lower cost, higher energy density, and reduced greenhouse gas emissions.

Selverston, Steven M.

395

Infrared Spectra of Ammonia-Water Ices  

NASA Astrophysics Data System (ADS)

We conducted a systematic study of the near-IR and mid-IR spectra of ammonia-water ices at various NH3/H2O ratios. The differences between the spectra of amorphous and crystalline ammonia-water ices were also investigated. The 2.0 ?m ammonia band central wavelength is a function of the ammonia/water ratio. It shifts from 2.006 ± 0.003 ?m (4985 ± 5 cm-1) to 1.993 ± 0.003 ?m (5018 ± 5 cm-1) as the percentage of ammonia decreases from 100% to 1%. The 2.2 ?m ammonia band center shifts from 2.229 ± 0.003 ?m (4486 ± 5 cm-1) to 2.208 ± 0.003 ?m (4528 ± 5 cm-1) over the same range. Temperature-dependent shifts of those bands are below the uncertainty of the measurement, and therefore are not detectable. These results are important for comparison with astronomical observations as well as for estimating the concentration of ammonia in outer solar system ices.

Zheng, Weijun; Jewitt, David; Kaiser, Ralf I.

2009-03-01

396

The Three Rs: Reduce, Reuse, Recycle.  

ERIC Educational Resources Information Center

A student hand-out for a recycling unit defines the terms reduce, recycle, and reuse as they relate to solid waste management. Presents the characteristics of recyclable items such as yard wastes, metals, glass, and paper. Lists organizations through which more information about recycling can be obtained. (MCO)

Science Activities, 1991

1991-01-01

397

EXPLAINING RURAL HOUSEHOLD PARTICIPATION IN RECYCLING  

Microsoft Academic Search

Rising landfill costs have forced solid waste managers to consider waste stream reduction alternatives such as household recycling. Explaining the factors which motivate households to recycle is important to regions where households must bear a large portion of the recycling cost because unit-based garbage disposal fees and curbside recycling are not feasible options. Empirical results indicate that residents are responsive

Paul M. Jakus; Kelly H. Tiller; William M. Park

1997-01-01

398

An industry response to recycle 2000  

Microsoft Academic Search

The US DOE is expected to issue a policy early this year articulating DOE`s position on the recycle of DOE radioactive scrap metal. In anticipation of this `Recycle 2000` initiative, the nuclear industry has formed a new trade association called the Association of Radioactive Metal Recyclers (ARMR). This article describes the Recycle 2000 initiative, provides some background on the ARMR

G. P. Motl; V. Loiselle

1996-01-01

399

Ammonia blockade of intestinal epithelial K+ conductance.  

PubMed

Ammonia profoundly inhibits cAMP-dependent Cl- secretion in model T84 human intestinal crypt epithelia. Because colonic lumen concentrations of ammonia are high (10-70 mM), ammonia may be a novel regulator of secretory diarrheal responsiveness. We defined the target of ammonia action by structure-function analysis with a series of primary amines (ammonia, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, and octylamine) that vary principally in size and lipid solubilities. The amine concentrations required for 50% inhibition of Cl- secretion in intact monolayers and 50% inhibition of outward K+ current (IK) in apically permeabilized monolayers vs. the logs of the respective amine partition coefficients give two plots that are strikingly similar in character. Half-maximal inhibition of short-circuit current (Isc) by ammonia was seen at 6 mM and for IK at 4 mM; half-maximal inhibition for octylamine was 0.24 mM and 0.19 mM for Isc and IK, respectively. The preferentially water-soluble hydrophilic amines (ammonia, methylamine, ethylamine) increase in blocking ability with decreasing size and lipophilicity. Conversely, the preferentially lipid-soluble hydrophobic (propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine) amines increase in blocking ability with increasing size and lipophilicity. Ammonia does not affect isolated apical Cl- conductance; amine-induced changes in cytosolic and endosomal pH do not correlate with secretory inhibition. We propose that ammonia in its protonated ammonium form (NH4+) inhibits cAMP-dependent Cl- secretion in T84 monolayers by blocking basolateral K+ channels. PMID:10484376

Hrnjez, B J; Song, J C; Prasad, M; Mayol, J M; Matthews, J B

1999-09-01

400

Recycling Plant for Paint Sludges.  

National Technical Information Service (NTIS)

The efficiency of paint spraying is, according to present technology, not satisfactory because the percentage of overspraying is too big. A pilot plant demonstrated that the amount of overspray can be reduced and the paint sludge can be recycled, resultin...

K. H. Berewinkel

1981-01-01

401

Recycling Practices for Environmental Materials.  

National Technical Information Service (NTIS)

Two environmental materials, tree and brush debris and large animal roadkill carcasses were investigated. The disposal methods for these materials were reviewed as opportunities/methods for possible recycling. KYTC established several pilot composting ope...

S. Palle S. Higgins T. Hopwood

2007-01-01

402

Disposal, Degradation, and Recycling; Bioplastics  

NSDL National Science Digital Library

Everyone is familiar with plastic waste. We throw away large volumes of it, at home, at school, at work, at fast food restaurants, on vacation. Much of it ends up in the trash. We see some of it as litter along the sides of roads, streams and lakes, and floating up on beaches. We probably recycle some used plastics, although how much depends upon where we live. In many localities, only items produced from PET (polyethylene terephthalate) and HDPE (high-density polyethylene) are collected for recycling. Why don't we recycle more of it? Why not LDPE (low-density polyethylene) and polystyrene? And what happens to it when we do? We'll develop some basic principles in this chapter on some of the avenues that help us follow the U.S. Environmental Protection Agency's advice to "reduce, reuse, recycle."

Teegarden, David

2004-01-01

403

Proliferation aspects of plutonium recycling  

Microsoft Academic Search

Plutonium recycling offers benefits in an energy perspective of sustainable development, and, moreover it contributes to non-proliferation. Prior to recycling, reactor-grade plutonium from light-water reactors does not lend itself easily to the assembly of explosive nuclear devices; thereafter, practically not at all. Control systems for material security and non-proliferation should identify and adopt several categories of plutonium covering various isotopic

Bruno Pellaud

2002-01-01

404

National Recycling Directory. Final report  

SciTech Connect

The directory focuses on manufacturers and/or distributors of products made from waste materials. Companies listed in the directory manufacture products which contain some recycled or recovered material. The directory consists of separate sections for the types of recycled materials used: glass, ferrous metals, non-ferrous metals, paper, plastic, rubber, and textiles. The states are listed alphabetically within each subsection, and the companies are listed alphabetically under the state in which they are located.

Not Available

1982-01-01

405

A feasibility study of implementing an Ammonia Economy  

Microsoft Academic Search

This thesis reports the results of a feasibility study performed on the concept of an Ammonia Economy, which treats ammonia as an alternative fuel and energy storage mechanism. As part of the Ammonia Economy, costs for production, storage, and transportation of this alternative fuel are also presented. The cost of hydrogen, which is the main feedstock for ammonia production, was

Jeffrey Ralph Bartels

2008-01-01

406

Percolative Theory of Organic Magnetoresistance and Fringe-Field Magnetoresistance  

NASA Astrophysics Data System (ADS)

A recently-introduced percolation theory [1,2] for spin transport and magnetoresistance in organic semiconductors describes the effects of spin dynamics on hopping transport by considering changes in the effective density of hopping sites, a key quantity determining the properties of percolative transport. Increases in the spin-flip rate open up ``spin-blocked'' pathways to become viable conduction channels and hence, as the spin-flip rate changes with magnetic field, produce magnetoresistance. Features of this percolative magnetoresistance can be found analytically in several regimes, and agree with measurements of the shape and saturation of measured magnetoresistance curves [3-5]. We find that the threshold hopping distance is analogous to the branching parameter of a phenomenological two-site model [6], and that the distinction between slow and fast hopping is contingent on the threshold hopping distance. Regimes of slow and fast hopping magnetoresistance are uniquely characterized by their line shapes. Studies of magnetoresistance in known systems with controllable positional disorder would provide an additional stringent test of this theory. Extensions to this theory also describe fringe-field magnetoresistance, which is the influence of fringe magnetic fields from a nearby unsaturated magnetic electrode on the conductance of an organic film [7]. This theory agrees with several key features of the experimental fringe-field magnetoresistance, including the applied fields where the magnetoresistance reaches extrema, the applied field range of large magnetoresistance effects from the fringe fields, and the sign of the effect. [4pt] All work done in collaboration with N. J. Harmon, and fringe-field magnetoresistance work in collaboration also with F. Macià, F. Wang, M. Wohlgenannt and A. D. Kent. This work was supported by an ARO MURI.[4pt] [1] N. J. Harmon and M. E. Flatté, PRL 108, 186602 (2012).[0pt] [2] N. J. Harmon and M. E. Flatté, PRB 85, 075204 (2012).[0pt] [3] F. L. Bloom et al, PRL 99, 257201 (2007).[0pt] [4] T. D. Nguyen et al., Nature Materials 9, 345 (2010)[0pt] [5] J. A. Gomez et al., Synth. Met. 160, 317 (2010)[0pt] [6] W. Wagemans et al., JAP 103, 07F303 (2008).[0pt] [7] F. Wang et al., PRX 2, 021013 (2012).

Flatté, Michael E.

2013-03-01

407

Direct Ammonia-Air Fuel Cell.  

National Technical Information Service (NTIS)

Experimental runs were conducted on direct ammonia fuel cells. Effects of temperature, composition, as well as run effect and block effect were investigated extensively through a statistical study program. The block effect was due to the employment of two...

R. E. Kuppinger

1964-01-01

408

Ammonia emissions during vermicomposting of sheep manure.  

PubMed

The effect of C:N ratio, temperature and water content on ammonia volatilization during two-phase composting of sheep manure was evaluated. The aerobic phase was conducted under field conditions. This was followed by Phase II, vermicomposting, conducted in the laboratory under controlled conditions of water content (70% and 80%) and temperature (15 and 22 °C). The addition of extra straw lead to a 10% reduction in NH3 volatilization compared to sheep manure composted without extra straw. Temperature and water content significantly effected ammonia volatilization at 0 day in Phase II, with a water content of 70% and temperature of 22 °C leading to greater losses of ammonia. Nitrogen loss by ammonia volatilization during vermicomposting ranged from 8% to 15% of the initial N content. The addition of extra straw did not result in significant differences in total carbon content following vermicomposting. PMID:21996478

Velasco-Velasco, Joel; Parkinson, Robert; Kuri, Victor

2011-12-01

409

Final Report: Sensor System to Monitor Ammonia.  

National Technical Information Service (NTIS)

This final technical report summarizes the results of a project to develop a prototype integrated optic ammonia NHJ sensor for agricultural and industrial applications. The majority of the support for this project was provided by the Department of Energy ...

J. G. Edwards

1999-01-01

410

INVESTIGATION OF THE ORION RESEARCH AMMONIA MONITOR  

EPA Science Inventory

The Orion Research ammonia monitor was investigated using the Orion specifications and environmental considerations as a guide. Laboratory tests under controlled environmental conditions showed the electronic stability (drift) to be well within + or - 10 percent of reading over t...

411

Zeolite Ammonia Removal from Catfish Pond Waters.  

National Technical Information Service (NTIS)

The problem of fish production can also be resolved by increasing fish density in existing ponds. Unfortunately, increasing fish density would also produce toxic buildup of ammonia and nitrate. The problem, however, can be alleviated by employing an ammon...

W. R. Reynolds C. W. Williford

1988-01-01

412

Defences against ammonia toxicity in tropical air-breathing fishes exposed to high concentrations of environmental ammonia: a review  

Microsoft Academic Search

In the tropics, air-breathing fishes can be exposed to environmental ammonia when stranded in puddles of water during the dry season, during a stay inside a burrow, or after agricultural fertilization. At low concentrations of environmental ammonia, NH 3 excretion is impeded, as in aerial exposure, leading to the accumulation of endogenous ammonia. At high concentrations of environmental ammonia, which

Y. K. Ip; S. F. Chew; J. M. Wilson; D. J. Randall

2004-01-01

413

Rethinking Recycling in Arcs  

NASA Astrophysics Data System (ADS)

Hacker et al EPSL 2011 and Behn et al Nature Geosci 2011 investigated pathways for return of buoyant, subducted material to arc crust. These include (1) diapirs rising into the hot mantle wedge, with extensive melts adding a component to arc magmas, (2) flow of material back up a relatively cold "subduction channel", adding solids to the lower crust and small-degree partial melts to the upper crust, (3) flow from the forearc along the base of arc crust, and (4) imbrication of forearc material into arc crust. These processes add felsic, incompatible-element-rich components to arc crust. The flux of incompatible elements such as Th in arc lavas, thought to be mainly recycled from subducted sediments, is > sediment subduction flux. There are large uncertainties: arc crustal growth rates are imprecise; young, primitive arc lavas may not be representative of magmatic flux into arc crust; sediment subduction flux may have varied. Nevertheless, this result is found for all arcs examined, using recently published growth rates. Perhaps arc growth rates that include subduction erosion are systematically overestimated. Instead or in addition, maybe significant Th comes from material other than sediments. Here, we consider the implications of pathways 1-4 for arc growth rates and incompatible element enrichment, in the context of subduction erosion and arc-arc collision. Subducting arc lithologies can become separated, with only felsic components returned to arc crust. Buoyant lithologies are mobile in viscous instabilities at > 700-800°C. Whereas thin layers such as sediments may become mobile all at once, instabilities may periodically strip the hottest parts from the top of thick buoyant layers, replacing them with hot mantle. In arc-arc collision, the top of a subducting plate starts at about 0°C on the seafloor, so heating is slow. In subduction erosion, forearc material in the subducting package can be > 200°C before erosion so buoyant lithologies reach 700-800°C faster, and in larger volumes at a given time. Subduction erosion rarely, if ever, transports significant amounts of buoyant material deep into the convecting mantle. Because buoyant material can remain part of the crust, it may often be a mistake to add all of the eroded material to the observed arc volume to derive crustal growth rates. Buoyancy instabilities during subduction erosion or arc-arc collision will accumulate felsic arc crust. For example, > 50% of Aleutian arc lavas and exposed plutons are more buoyant than mantle peridotite at 700-800°C, 3-4 GPa. The buoyant material has an average of 60-62 wt% SiO2, molar Mg/(Mg+Fe) 0.4-0.5, and trace elements identical to bulk continental crust, though western Aleutian lavas have the most depleted Sr, Nd and Pb isotope ratios of all arc lavas worldwide. In general, density sorting of arc lithologies, and subsequent partial melting as buoyant rocks rise through the mantle wedge or along a subduction channel, could lead to a kind of double and triple distillation. Incompatible elements such as Th would be enriched in arc crust, retaining correlations with isotopic indicators of a recycled sediment component, while Th-poor, dense, mafic lavas and lower crustal cumulates return to the convecting mantle.

Kelemen, P.; Behn, M. D.; Jagoutz, O.

2012-12-01

414

Deep Recycling of Carbon  

NASA Astrophysics Data System (ADS)

While most of the subducted H2O is recycled at shallow and subarc depths, carbon is less readily mobilized and susceptive to complex redox processes involving CO2 in solids, fluids and melts, elemental carbon, Fe- and Si- carbides, and methane. Here I review the various ways of recycling carbon during subduction and present a spectrum of possible reaction products in the mantle. Metamorphic reactions liberate <20% of the subducted CO2 to the subarc region (Connolly 2005, EPSL). Larger amounts might be mobilized through (sediment) melting. Although the wet pelite solidus is only shifted by 30-50 oC (at 3 GPa) with carbonates, the latter remain stable with melts that are saturated in a H2O+CO2-fluid. Complete dissolution of carbonates requires temperatures above any predicted subduction geotherm. Carbonated sediments yield CO2-rich phonolites to 5 GPa but carbonatites at higher pressures. The silicate melts become increasingly potassic with pressure, while the alkali-rich carbonatites have their highest K/Na at 8 GPa, slightly decreasing to 13 GPa and become sodic with the disappearance of residual cpx at ~16 GPa. What may happen when carbonated pelite derived melts migrate into the mantle is illustrated in Central Italy: in this case, it can be experimentally demonstrated that hybridization of ultrapotassic phonolitic melts with ~2 wt% H2O and ~6 wt% CO2 in the mantle results in the primitive parents of the ultrapotassic kamafugite suites which have ~43 wt% SiO2. Hence, despite a crustal isotopic signature of C, O, and Sr in these rocks, the CO2 of the Italian magmatism does not stem from assimilation in the crust but from melts derived from subducted marine carbonates mixed with pelagic clays and then reacted in the mantle. The migration of CO2-bearing fluids and melts into the mantle may lead to a redox-shock. Where high liquid/mantle ratios prevail, carbonatites rest in their oxidized form and may only freeze in relatively cold lithospheric keels where they form metasomatic zones prone to generate kimberlites in the context of a much later remelting event. Where the redox-capacity of the oxidized crust-derived material is subequal to the reduced mantle, iron carbides are to be expected. The eutectic in the Fe-Ni-C system is at lower temperatures than the mantle adiabat, leading to the distinct possibility that such zones entrained in global mantle convection will contain ~1% of eutectic Fe-C-melt. When the amount of subduction derived CO2 is small compared to the redox capacity of a metal bearing reduced mantle, diamond will form, but diamond itself is not truly reducing at high pressures. The most extreme reducing case leads to moissanite (found together with diamond), which isotopic signature implies involvement of organically derived carbon. Moissanite (SiC) only forms at fO2 <6-8 log units below iron-wustite and coexists with mantle silicates that have an XMg of 0.995-0.998. Our calculations show that a fluid or melt with a bulk, which is slightly more reduced than the CO2-H2O-tieline in C-O-H, may evolve to ultra-reduced residual C-H-rich fluids through removal of CO2 (through carbonate precipitation) followed by removal of H2O (through hydrous silicate formation). As SiC may only be in grain scale equilibrium with the mantle and requires a protracted fluid-fractionation, we propose that SiC is generally a low temperature phase formed from originally already reducing fluids involving organic carbon and hence subduction.

Schmidt, M. W.

2012-12-01

415

Hoso haikibutsu recycle system ni kansuru chosa. (Survey on the package waste recycling system).  

National Technical Information Service (NTIS)

On the establishment of 'the Package Recycling Law,' a survey on the present situation and extraction of subjects were made to expedite the recycling of package containers. Conventionally, package recycling has been regarded as a job peculiar to each loca...

1996-01-01

416

50 Simple Things Kids Can Do To Recycle. California Edition.  

ERIC Educational Resources Information Center

This book provides 50 recycling ideas for children and features Recycle Rex, the state of California's "spokesdinosaur" for recycling. An introduction contains recycling background information on waste disposal options and reducing, reusing, and recycling. Recycling suggestions are divided into nine sections: (1) "Learn What You Can Recycle"…

Javna, John

417

Process studies of water percolation in a Mediterranean karst area  

NASA Astrophysics Data System (ADS)

In drylands karst environments comprise large areas and their groundwater resources are important for local and regional water supply. Recharge estimations are usually based on long term averages and hence uncertain, because they do not explicitly account for the accentuated variability of dryland precipitation, where a large fraction of annual rainfall is concentrated in a small number of high magnitude events. To provide process information in adequate temporal resolution the present study directly investigates percolation processes in an Eastern Mediterranean karst system, Mt. Carmel, Israel. Therefore the drip response of stalactites in a karstic cave 28m below a sprinkling experiment was measured. Besides hydrometric measurements (soil moisture, surface runoff, stalactite dripping rates) also tracers were applied. Sprinkling water was pumped from two wells of the underlying karst aquifer. The experiment took place at the end of the dry season. Simulating a series of two high intensity storms, 190 mm of artificial rainfall was sprinkled over two days on a 143 m2 plot. Two types of tracers were used: (i) the relatively high conductivity of the sprinkling water facilitated the separation between old (pre-sprinkling) and new (sprinkling) water by mixing analysis, (ii) before second day sprinkling bromide was injected as a dirac impulse on top of selected soil pockets to facilitate direct insights into percolation fluxes. On the plot surface saturation excess runoff was observed towards the end of first day sprinkling and entire soil saturation occurred down to the deepest soil moisture sensor. During the second day the entire soil reached quickly saturation and remained at field capacity until the end of data collection. In the cave the drip response depended on stalactite type: (i) perennial stalactites were already dripping continuously before sprinkling onset. Conductivity dynamics resulted in high percentages of pre-sprinkling water suggesting continuous input from the fissured rock matrix. (ii) dripping at the other stalactites initiated only after sprinkling and was mainly made of event water following preferential flow paths. Although bromide was injected prior to second day sprinkling its breakthrough was delayed at every location compared to drip response. This suggested piston flow effects at high moisture states. Two-part recession dynamics of the bromide breakthrough curves suggested different percolation mechanisms: Until about 24h after sprinkling a quick recession indicated preferential flow paths, while thereafter a delayed recession suggested mixing in epikarst reservoirs. Over the entire experiment quick percolation as collected in the drips was in the same range as estimated evaporation losses during the 2 days sprinkling (both about 6%). Most water filled up empty soil pockets (about 32%) or epikarst storages (about 53%). Despite soil saturation very little surface runoff (about 2%) was generated. In a 36 km2 catchment the experimental findings are now being used as input for high-resolution water balance modelling.

Lange, J.; Arbel, Y.; Greenbaum, N.; Grodek, T.

2009-04-01

418

Field-Induced Percolation of Polar Nanoregions in Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

A first-principles-based effective Hamiltonian is used to investigate low-temperature properties of Ba(Zr,Ti)O3 relaxor ferroelectrics under an increasing dc electric field. This system progressively develops an electric polarization that is highly nonlinear with the dc field. This development leads to a maximum of the static dielectric response at a critical field, Eth, and involves four different field regimes. Each of these regimes is associated with its own behavior of polar nanoregions, such as shrinking, flipping, and elongation of dipoles or change in morphology. The clusters propagating inside the whole sample, with dipoles being parallel to the field direction, begin to form at precisely the Eth critical field. Such a result, and further analysis we perform, therefore, reveal that field-induced percolation of polar nanoregions is the driving mechanism for the transition from the relaxor to ferroelectric state.

Prosandeev, S.; Wang, Dawei; Akbarzadeh, A. R.; Dkhil, B.; Bellaiche, L.

2013-05-01

419

Emergent spin excitations in a Bethe lattice at percolation.  

PubMed

We study the spin-1/2 quantum Heisenberg antiferromagnet on a Bethe lattice diluted to the percolation threshold. Dilution creates areas of even or odd sublattice imbalance resulting in "dangling spins" [L. Wang and A. W. Sandvik, Phys. Rev. Lett. 97, 117204 (2006); Phys. Rev. B 81, 054417 (2010)]. These collectively act as "emergent" spin-1/2 degrees of freedom and are responsible for the creation of a set of low-lying "quasidegenerate states." Using density matrix renormalization group calculations, we detect the presence and location of these emergent spins. We find an effective Hamiltonian of these emergent spins, with Heisenberg interactions that decay exponentially with the distance between them. PMID:24160622

Changlani, Hitesh J; Ghosh, Shivam; Pujari, Sumiran; Henley, Christopher L

2013-10-11

420

Evidence for enhanced thermal conduction through percolating structures in nanofluids.  

PubMed

The unusually large enhancement of thermal conductivity (k/k(f)?4.0, where k and k(f) are the thermal conductivities of the nanofluid and the base fluid, respectively) observed in a nanofluid containing linear chain-like aggregates provides direct evidence for efficient transport of heat through percolating paths. The nanofluid used was a stable colloidal suspension of magnetite (Fe(3)O(4)) nanoparticles of average diameter 6.7 nm, coated with oleic acid and dispersed in kerosene. The maximum enhancement under magnetic field was about 48? (where ? is the volume fraction). The maximum enhancement is observed when chain-like aggregates are uniformly dispersed without clumping. These results also suggest that nanofluids containing well-dispersed nanoparticles (without aggregates) do not exhibit significant enhancement of thermal conductivity. Our findings offer promising applications for developing a new generation of nanofluids with tunable thermal conductivity. PMID:21828773

Philip, John; Shima, P D; Raj, Baldev

2008-07-30

421

Percolation and permeability of fracture networks in Excavated Damaged Zones  

NASA Astrophysics Data System (ADS)

Generally, the excavation process of a gallery generates fractures in its immediate vicinity. The corresponding zone which is called the Excavated Damaged Zone (EDZ), has a larger permeability than the intact surrounding medium. The properties of the EDZ are attracting more and more attention because of their potential importance in repositories of nuclear wastes. The EDZ which is induced by the excavation process may create along the galleries of the repositories a high permeability zone which could directly connect the storage area with the ground surface. Therefore, the studies of its properties are of crucial importance for applications such as the storage of nuclear wastes. Field observations (such as the ones which have been systematically performed at Mont Terri by [1, 2]) suggest that the fracture density is an exponentially decreasing function of the distance to the wall with a characteristic length of about 0.5 m and that the fracture orientation is anisotropic (most fractures are subparallel to the tunnel walls) and well approximated by a Fisher law whose pole is orthogonal to the wall. Numerical samples are generated according to these prescriptions. Their percolation status and hydraulic transmissivity can be calculated by the numerical codes which are detailed in [3]. Percolation is determined by a pseudo diffusion algorithm. Flow determination necessitates the meshing of the fracture networks and the discretisation of the Darcy equation by a finite volume technique; the resulting linear system is solved by a conjugate gradient algorithm. Only the flow properties of the EDZ along the directions which are parallel to the wall are of interest when a pressure gradient parallel to the wall is applied. The transmissivity T which relates the total flow rate per unit width Q along the wall through the whole EDZ to the pressure gradient grad p, is defined by Q = - T grad p/mu where mu is the fluid viscosity. The percolation status and hydraulic transmissivity are systematically determined for a wide range of decay lengths and anisotropy parameters. They can be modeled by comparison with anisotropic fracture networks with a constant density. A heuristic power-law model is proposed which accurately describes the results for the percolation threshold over the whole investigated range of heterogeneity and anisotropy. Then, the data for the EDZ transmissivity are presented. A simple parallel flow model is introduced. The flow properties of the EDZ vary with the distance z from the wall. However, the macroscopic pressure gradient does not depend on z, and the flow lines are in average parallel to the wall. Hence, the overall transmissivity is tentatively estimated by a parallel flow model, where a layer at depth z behaves as a fractured medium with uniform properties corresponding to the state at this position in the EDZ. It yields an explicit analytical expression for the transmissivity as a function of the heterogeneity and anisotropy parameters, and it successfully accounts for all the numerical data. Graphical tools are provided from which first estimates can be quickly and easily obtained. [1] Bossart P. et al, Eng. Geol., vol. 66, 19-38 (2002). [2] Thovert J.-F. et al, Eng. Geol., 117, 39-51 (2011). [3] Adler P.M. et al, Fractured porous media, Oxford U. Press, in press.

Mourzenko, V.; Thovert, J.; Adler, P. M.

2012-12-01

422

Benefits of current percolation in superconducting coated conductors  

SciTech Connect

The critical currents of coated conductors fabricated by metal-organic deposition (MOD) on rolling-assisted biaxially textured substrates (RABiTS) and by pulsed laser deposition (PLD) on ion-beam assisted deposition (IBAD) templates have been measured as a function of magnetic field orientation and compared to films grown on single crystal substrates. By varying the orientation of magnetic field applied in the plane of the film, we are able to determine the extent to which current flow in each type of conductor is percolative. Standard MOD/RABiTS conductors have also been compared to samples whose grain boundaries have been doped by diffusing Ca from an overlayer. We find that undoped MOD/RABiTS tapes have a less anisotropic in-plane field dependence than PLD/IBAD tapes and that the uniformity of critical current as a function of in-plane field angle is greater for MOD/RABiTS samples doped with Ca.

Rutter, N.A.; Durrell, J.H.; Blamire, M.G.; MacManus-Driscoll, J.L.; Wang, H.; Foltyn, S.R. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2005-10-17

423

Ammonia sensors based on metal oxide nanostructures  

Microsoft Academic Search

Ammonia sensing characteristics of nanoparticles as well as nanorods of ZnO, In2O3 and SnO2 have been investigated over a wide range of concentrations (1–800 ppm) and temperatures (100–300 °C). The best values of sensitivity are found with ZnO nanoparticles and SnO2 nanostructures. Considering all the characteristics, the SnO2 nanostructures appear to be good candidates for sensing ammonia, with sensitivities of

Chandra Sekhar Rout; Manu Hegde; A Govindaraj; C N R Rao

2007-01-01

424

A wireless, remote query ammonia sensor  

Microsoft Academic Search

This paper presents a wireless, remote query ammonia sensor comprised of a free-standing magnetoelastic thick-film coated with a polymer, poly(acrylic acid-co-isooctylacrylate), that changes mass in response to atmospheric ammonia concentration. The mass of the polymer layer modulates the resonant frequency the ferromagnetic magnetoelastic substrate, hence by monitoring the frequency response of the sensor, atmospheric NH3 concentration can be determined remotely,

Qing Y. Cai; Mahaveer K. Jain; Craig A. Grimes

2001-01-01

425

YBCO-FET room temperature ammonia sensor  

Microsoft Academic Search

A FET-ammonia sensor operating at room temperature is reported in this paper. The sensor employs a thin film of semiconducting Y:Ba:Cu:O (YBCO) compound, commonly known as 1-2-3 high temperature superconducting cuprate, as its sensing element. We observed that this material is highly and selectively sensitive to ammonia at and below room temperature. The measurements indicate that the non-amplified signal of

R. P Gupta; Z Gergintschew; D Schipanski; P. D Vyas

2000-01-01

426

Ammonia Policy Context and Future Challenges  

Microsoft Academic Search

Ammonia emissions are major contributors to eutrophication and acidification of ecosystems and secondary PM2.5 concentrations in Europe. Reduction of the ammonia emissions in Europe has been on the agenda for more than a decade, first\\u000a on a national scale, e.g. in Denmark and the Netherlands, followed by international efforts. The latter include the UNECE\\u000a CLRTAP Gothenburg Protocol and EU directives

Till Spranger; Zbigniew Klimont; Michel Sponar; Caroline Raes; Samantha M. H. Baker; Mark A. Sutton; Collin Gillespie; Y. Sim Tang; Helle Vibeke Andersen; Thomas Ellerman; Chris Flechard; Nick J. Hutchings

427

Energy retrofit study of an ammonia plant  

Microsoft Academic Search

Detailed energy integration study of the front-end of an existing ammonia plant has been performed, using recent advances in Pinch technology. Utility loads demanded by the existing process were found to be very close to the calculated minimum targets. This indicated that the selected ammonia plant is well integrated, and not much saving is expected through process-to-process energy integration. Alternatively,

Haitham M. S Lababidi; Imad M Alatiqi; Lutfi J Nayfeh

2000-01-01

428

An indirect ammonia-air fuel system  

Microsoft Academic Search

A rather simple ammonia-air fuel cell system has been developed in Wuhan University. Ammonia is cracked to give a 25% N2, 75% H2 gas mixture, which is consumed directly in the fuel cell stack. Scrubbed air is supplied to the air electrodes by the 'chimney effect'. No platinum-group metal catalysts are used to fabricate the electrodes and the system contains

C.-S. Cha; Z.-D. Wang; Y.-C. Chu; C.-T. Lo

1979-01-01

429

Scaling and percolation in the small-world network model.  

PubMed

In this paper we study the small-world network model of Watts and Strogatz, which mimics some aspects of the structure of networks of social interactions. We argue that there is one nontrivial length-scale in the model, analogous to the correlation length in other systems, which is well-defined in the limit of infinite system size and which diverges continuously as the randomness in the network tends to zero, giving a normal critical point in this limit. This length-scale governs the crossover from large- to small-world behavior in the model, as well as the number of vertices in a neighborhood of given radius on the network. We derive the value of the single critical exponent controlling behavior in the critical region and the finite size scaling form for the average vertex-vertex distance on the network, and, using series expansion and Padé approximants, find an approximate analytic form for the scaling function. We calculate the effective dimension of small-world graphs and show that this dimension varies as a function of the length-scale on which it is measured, in a manner reminiscent of multifractals. We also study the problem of site percolation on small-world networks as a simple model of disease propagation, and derive an approximate expression for the percolation probability at which a giant component of connected vertices first forms (in epidemiological terms, the point at which an epidemic occurs). The typical cluster radius satisfies the expected finite size scaling form with a cluster size exponent close to that for a random graph. All our analytic results are confirmed by extensive numerical simulations of the model. PMID:11970678

Newman, M E; Watts, D J

1999-12-01

430

Scaling and percolation in the small-world network model  

SciTech Connect

In this paper we study the small-world network model of Watts and Strogatz, which mimics some aspects of the structure of networks of social interactions. We argue that there is one nontrivial length-scale in the model, analogous to the correlation length in other systems, which is well-defined in the limit of infinite system size and which diverges continuously as the randomness in the network tends to zero, giving a normal critical point in this limit. This length-scale governs the crossover from large- to small-world behavior in the model, as well as the number of vertices in a neighborhood of given radius on the network. We derive the value of the single critical exponent controlling behavior in the critical region and the finite size scaling form for the average vertex-vertex distance on the network, and, using series expansion and Pade approximants, find an approximate analytic form for the scaling function. We calculate the effective dimension of small-world graphs and show that this dimension varies as a function of the length-scale on which it is measured, in a manner reminiscent of multifractals. We also study the problem of site percolation on small-world networks as a simple model of disease propagation, and derive an approximate expression for the percolation probability at which a giant component of connected vertices first forms (in epidemiological terms, the point at which an epidemic occurs). The typical cluster radius satisfies the expected finite size scaling form with a cluster size exponent close to that for a random graph. All our analytic results are confirmed by extensive numerical simulations of the model. (c) 1999 The American Physical Society.

Newman, M. E. J. [Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States)] [Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States); Watts, D. J. [Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States)] [Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States)

1999-12-01

431

Ammonia chemistry in a flameless jet  

SciTech Connect

In this paper, the nitrogen chemistry in an ammonia (NH{sub 3}) doped flameless jet is investigated using a kinetic reactor network model. The reactor network model is used to explain the main differences in ammonia chemistry for methane (CH{sub 4})-containing fuels and methane-free fuels. The chemical pathways of nitrogen oxides (NO{sub x}) formation and destruction are identified using rate-of-production analysis. The results show that in the case of natural gas, ammonia reacts relatively late at fuel lean condition leading to high NO{sub x} emissions. In the pre-ignition zone, the ammonia chemistry is blocked due to the absence of free radicals which are consumed by methane-methyl radical (CH{sub 3}) conversion. In the case of methane-free gas, the ammonia reacted very rapidly and complete decomposition was reached in the fuel rich region of the jet. In this case the necessary radicals for the ammonia conversion are generated from hydrogen (H{sub 2}) oxidation. (author)

Zieba, Mariusz; Schuster, Anja; Scheffknecht, Guenter [Institute of Process Engineering and Power Plant Technology, University of Stuttgart, Pfaffenwaldring 23, D-70569 Stuttgart (Germany); Brink, Anders; Hupa, Mikko [Process Chemistry Centre, Aabo Akademi University, Biskopsgatan 8, 20500 Aabo (Finland)

2009-10-15

432

Septic wastewater treatment using recycled rubber particles as biofiltration media.  

PubMed

Performance of the laboratory-scale recycled rubber particles (RRP) biofilter was compared to a conventional gravel system and a peat biofilter for treatment of septic tank effluent. During the study, the RRP biofilter provided similar or better performance than other systems in terms of organic removal and hydraulic capacity. After the start-up period, RRP biofilter achieved removal efficiencies for BOD5, total suspended solids (TSS), ammonia nitrogen of 96%, 93%, and 90%, respectively, over the range of hydraulic loading rates of 57-204 L/m2/d. On the other hand, the peat biofilter failed hydraulically and the gravel system showed high TSS concentrations in the effluent. RRP provided high surface area and sufficient time for biological treatment. In addition, RRP was observed to provide ammonia adsorption capacity. The results showed that RRP has the potential to be used as substitutes for natural aggregate such as gravel in septic system drainfields. The RRP biofilter can be used as alternative septic systems for the sites where an existing septic system has failed or site conditions, such as high groundwater table or small lot size, are not suitable for the installation of conventional septic systems. PMID:24645443

Oh, Jin Hwan; Park, Jaeyoung; Ellis, Timothy G

2014-01-01

433

What can recycling in thermal reactors accomplish?  

SciTech Connect

Thermal recycle provides several potential benefits when used as stop-gap, mixed, or backup recycling to recycling in fast reactors. These three roles involve a mixture of thermal and fast recycling; fast reactors are required to some degree at some time. Stop-gap uses thermal reactors only until fast reactors are adequately deployed and until any thermal-recycle-only facilities have met their economic lifetime. Mixed uses thermal and fast reactors symbiotically for an extended period of time. Backup uses thermal reactors only if problems later develop in the fast reactor portion of a recycling system. Thermal recycle can also provide benefits when used as pure thermal recycling, with no intention to use fast reactors. However, long term, the pure thermal recycling approach is inadequate to meet several objectives. (authors)

Piet, Steven J.; Matthern, Gretchen E.; Jacobson, Jacob J. [Idaho National Laboratory - INL, 2525 N. Fremont Avenue, Idaho Falls, ID 83415 (United States)

2007-07-01

434

What can Recycling in Thermal Reactors Accomplish?  

SciTech Connect

Thermal recycle provides several potential benefits when used as stop-gap, mixed, or backup recycling to recycling in fast reactors. These three roles involve a mixture of thermal and fast recycling; fast reactors are required to some degree at some time. Stop-gap uses thermal reactors only until fast reactors are adequately deployed and until any thermal-recycle-only facilities have met their economic lifetime. Mixed uses thermal and fast reactors symbiotically for an extended period of time. Backup uses thermal reactors only if problems later develop in the fast reactor portion of a recycling system. Thermal recycle can also provide benefits when used as pure thermal recycling, with no intention to use fast reactors. However, long term, the pure thermal recycling approach is inadequate to meet several objectives.

Steven Piet; Gretchen E. Matthern; Jacob J. Jacobson

2007-09-01

435

Two-dimensional continuum percolation threshold for diffusing particles of nonzero radius.  

PubMed

Lateral diffusion in the plasma membrane is obstructed by proteins bound to the cytoskeleton. The most important parameter describing obstructed diffusion is the percolation threshold. The thresholds are well known for point tracers, but for tracers of nonzero radius, the threshold depends on the excluded area, not just the obstacle concentration. Here thresholds are obtained for circular obstacles on the continuum. Random obstacle configurations are generated by Brownian dynamics or Monte Carlo methods, the obstacles are immobilized, and the percolation threshold is obtained by solving a bond percolation problem on the Voronoi diagram of the obstacles. The percolation threshold is expressed as the diameter of the largest tracer that can cross a set of immobile obstacles at a prescribed number density. For random overlapping obstacles, the results agree with the known analytical solution quantitatively. When the obstacles are soft disks with a 1/r(12) repulsion, the percolating diameter is approximately 20% lower than for overlapping obstacles. A percolation model predicts that the threshold is highly sensitive to the tracer radius. To our knowledge, such a strong dependence has so far not been reported for the plasma membrane, suggesting that percolation is not the factor controlling lateral diffusion. A definitive experiment is proposed. PMID:20816061

Saxton, Michael J

2010-09-01

436

Continuum percolation of overlapping disks with a distribution of radii having a power-law tail  

NASA Astrophysics Data System (ADS)

We study the continuum percolation problem of overlapping disks with a distribution of radii having a power-law tail; the probability that a given disk has a radius between R and R+dR is proportional to R-(a+1), where a>2. We show that in the low-density nonpercolating phase, the two-point function shows a power-law decay with distance, even at arbitrarily low densities of the disks, unlike the exponential decay in the usual percolation problem. As in the problem of fluids with long-range interaction, we argue that in our problem, the critical exponents take their short-range values for a>3-?sr whereas they depend on a for a<3-?sr where ?sr is the anomalous dimension for the usual percolation problem. The mean-field regime obtained in the fluid problem corresponds to the fully covered regime, a?2, in the percolation problem. We propose an approximate renormalization scheme to determine the correlation length exponent ? and the percolation threshold. We carry out Monte Carlo simulations and determine the exponent ? as a function of a. The determined values of ? show that it is independent of the parameter a for a>3-?sr and is equal to that for the lattice percolation problem, whereas ? varies with a for 2percolation threshold of the system as a function of the parameter a.

Sasidevan, V.

2013-08-01

437

Percolation, phase separation, and gelation in fluids and mixtures of spheres and rods.  

PubMed

The relationship between kinetic arrest, connectivity percolation, structure and phase separation in protein, nanoparticle, and colloidal suspensions is a rich and complex problem. Using a combination of integral equation theory, connectivity percolation methods, nai?ve mode coupling theory, and the activated dynamics nonlinear Langevin equation approach, we study this problem for isotropic one-component fluids of spheres and variable aspect ratio rigid rods, and also percolation in rod-sphere mixtures. The key control parameters are interparticle attraction strength and its (short) spatial range, total packing fraction, and mixture composition. For spherical particles, formation of a homogeneous one-phase kinetically stable and percolated physical gel is predicted to be possible, but depends on non-universal factors. On the other hand, the dynamic crossover to activated dynamics and physical bond formation, which signals discrete cluster formation below the percolation threshold, almost always occurs in the one phase region. Rods more easily gel in the homogeneous isotropic regime, but whether a percolation or kinetic arrest boundary is reached first upon increasing interparticle attraction depends sensitively on packing fraction, rod aspect ratio and attraction range. Overall, the connectivity percolation threshold is much more sensitive to attraction range than either the kinetic arrest or phase separation boundaries. Our results appear to be qualitatively consistent with recent experiments on polymer-colloid depletion systems and brush mediated attractive nanoparticle suspensions. PMID:22191900

Jadrich, Ryan; Schweizer, Kenneth S

2011-12-21

438

DWPF Recycle Evaporator Simulant Tests  

SciTech Connect

Testing was performed to determine the feasibility and processing characteristics of an evaporation process to reduce the volume of the recycle stream from the Defense Waste Processing Facility (DWPF). The concentrated recycle would be returned to DWPF while the overhead condensate would be transferred to the Effluent Treatment Plant. Various blends of evaporator feed were tested using simulants developed from characterization of actual recycle streams from DWPF and input from DWPF-Engineering. The simulated feed was evaporated in laboratory scale apparatus to target a 30X volume reduction. Condensate and concentrate samples from each run were analyzed and the process characteristics (foaming, scaling, etc) were visually monitored during each run. The following conclusions were made from the testing: Concentration of the ''typical'' recycle stream in DWPF by 30X was feasible. The addition of DWTT recycle streams to the typical recycle stream raises the solids content of the evaporator feed considerably and lowers the amount of concentration that can be achieved. Foaming was noted during all evaporation tests and must be addressed prior to operation of the full-scale evaporator. Tests were conducted that identified Dow Corning 2210 as an antifoam candidate that warrants further evaluation. The condensate has the potential to exceed the ETP WAC for mercury, silicon, and TOC. Controlling the amount of equipment decontamination recycle in the evaporator blend would help meet the TOC limits. The evaporator condensate will be saturated with mercury and elemental mercury will collect in the evaporator condensate collection vessel. No scaling on heating surfaces was noted during the tests, but splatter onto the walls of the evaporation vessels led to a buildup of solids. These solids were difficult to remove with 2M nitric acid. Precipitation of solids was not noted during the testing. Some of the aluminum present in the recycle streams was converted from gibbsite to aluminum oxide during the evaporation process. The following recommendations were made: Recycle from the DWTT should be metered in slowly to the ''typical'' recycle streams to avoid spikes in solids content to allow consistent processing and avoid process upsets. Additional studies should be conducted to determine acceptable volume ratios for the HEME dissolution and decontamination solutions in the evaporator feed. Dow Corning 2210 antifoam should be evaluated for use to control foaming. Additional tests are required to determine the concentration of antifoam required to prevent foaming during startup, the frequency of antifoam additions required to control foaming during steady state processing, and the ability of the antifoam to control foam over a range of potential feed compositions. This evaluation should also include evaluation of the degradation of the antifoam and impact on the silicon and TOC content of the condensate. The caustic HEME dissolution recycle stream should be neutralized to at least pH of 7 prior to blending with the acidic recycle streams. Dow Corning 2210 should be used during the evaporation testing using the radioactive recycle samples received from DWPF. Evaluation of additional antifoam candidates should be conducted as a backup for Dow Corning 2210. A camera and/or foam detection instrument should be included in the evaporator design to allow monitoring of the foaming behavior during operation. The potential for foam formation and high solids content should be considered during the design of the evaporator vessel.

Stone, M

2005-04-05

439

Recycling perturbations of supershot plasmas  

SciTech Connect

Thermal heat transport in the core (r/a {le} 0.5) of beam-heated TFTR plasmas vanes by more than a factor of five between L-mode and supershot plasmas for the same I{sub p}, B{sub T}, and P{sub b}. Operationally, this variation is strongly correlated with the particle recycling coefficient of the carbon-carbon composite inner bumper limiter. The mechanisms underlying this correlation are not understood. This paper describes studies of the edge ion temperature, which is an important parameter if {tau}{sub E} is controlled by ion temperature gradient driven turbulence. We find that a edge electron temperature scales simply with power per electron, irrespective of the recycling state of the limiter. By contrast, the scaling of edge ion temperature is strongly affected by the recycling state of the limiter. Much higher edge ion temperatures are attained in low-recycling plasmas for the same power per particle. In addition, perturbative studies of recycling effects on transport have been carried out by puffing in large amounts of helium into a supershot plasma. The local core transport coefficients increase on a transport time scale ({approximately}100 ms), much faster than the current relaxation time scale. This suggests that the current profile is not responsible for the favorable energy confinement of supershot plasmas relative to L-mode plasmas.

Scott, S.D.; McCune, D.C.; Bell, M.G.; Bell, R.; Budny, R.V.; Fredrickson, E.; Grek, B.; Hill, K.W.; Jassby, D.; Jobes, F.; Johnson, D.W.; Johnson, L.C.; Mansfield, H.K.; Park, H.K.; Ramsey, A.T.; Stratton, B.E.; Synakowski, E.J.; Taylor, G.; Towner, H.H.; Zarnstorff, M.C. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Snipes, J.A. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1993-03-01

440

Recycling perturbations of supershot plasmas  

SciTech Connect

Thermal heat transport in the core (r/a [le] 0.5) of beam-heated TFTR plasmas vanes by more than a factor of five between L-mode and supershot plasmas for the same I[sub p], B[sub T], and P[sub b]. Operationally, this variation is strongly correlated with the particle recycling coefficient of the carbon-carbon composite inner bumper limiter. The mechanisms underlying this correlation are not understood. This paper describes studies of the edge ion temperature, which is an important parameter if [tau][sub E] is controlled by ion temperature gradient driven turbulence. We find that a edge electron temperature scales simply with power per electron, irrespective of the recycling state of the limiter. By contrast, the scaling of edge ion temperature is strongly affected by the recycling state of the limiter. Much higher edge ion temperatures are attained in low-recycling plasmas for the same power per particle. In addition, perturbative studies of recycling effects on transport have been carried out by puffing in large amounts of helium into a supershot plasma. The local core transport coefficients increase on a transport time scale ([approximately]100 ms), much faster than the current relaxation time scale. This suggests that the current profile is not responsible for the favorable energy confinement of supershot plasmas relative to L-mode plasmas.

Scott, S.D.; McCune, D.C.; Bell, M.G.; Bell, R.; Budny, R.V.; Fredrickson, E.; Grek, B.; Hill, K.W.; Jassby, D.; Jobes, F.; Johnson, D.W.; Johnson, L.C.; Mansfield, H.K.; Park, H.K.; Ramsey, A.T.; Stratton, B.E.; Synakowski, E.J.; Taylor, G.; Towner, H.H.; Zarnstorff, M.C. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Snipes, J.A. (Massachusetts Inst. of Tech., Cambridge, MA (United States))

1993-03-01

441

Recycling of polymers: a review.  

PubMed

Plastics are inexpensive, easy to mold, and lightweight. These and many other advantages make them very promising candidates for commercial applications. In many areas, they have substantially suppressed traditional materials. However, the problem of recycling still is a major challenge. There are both technological and economic issues that restrain the progress in this field. Herein, a state-of-art overview of recycling is provided together with an outlook for the future by using popular polymers such as polyolefins, poly(vinyl chloride), polyurethane, and poly(ethylene terephthalate) as examples. Different types of recycling, primary, secondary, tertiary, quaternary, and biological recycling, are discussed together with related issues, such as compatibilization and cross-linking. There are various projects in the European Union on research and application of these recycling approaches; selected examples are provided in this article. Their progress is mirrored by granted patents, most of which have a very limited scope and narrowly cover certain technologies. Global introduction of waste utilization techniques to the polymer market is currently not fully developed, but has an enormous potential. PMID:24811748

Ignatyev, Igor A; Thielemans, Wim; Vander Beke, Bob

2014-06-01

442

Consolidated conversion of protein waste into biofuels and ammonia using Bacillus subtilis.  

PubMed

The non-recyclable use of nitrogen fertilizers in microbial production of fuels and chemicals remains environmentally detrimental. Conversion of protein wastes into biofuels and ammonia by engineering nitrogen flux in Escherichia coli has been demonstrated as a method to reclaim reduced-nitrogen and curb its environmental deposition. However, protein biomass requires a proteolysis process before it can be taken up and converted by any microbe. Here, we metabolically engineered Bacillus subtilis to hydrolyze polypeptides through its secreted proteases and to convert amino acids into advanced biofuels and ammonia fertilizer. Redirection of B. subtilis metabolism for amino-acid conversion required inactivation of the branched-chain amino-acid (BCAA) global regulator CodY. Additionally, the lipoamide acyltransferase (bkdB) was deleted to prevent conversion of branched-chain 2-keto acids into their acyl-CoA derivatives. With these deletions and heterologous expression of a keto-acid decarboxylase and an alcohol dehydrogenase, the final strain produced biofuels and ammonia from an amino-acid media with 18.9% and 46.6% of the maximum theoretical yield. The process was also demonstrated on several waste proteins. The results demonstrate the feasibility of direct microbial conversion of polypeptides into sustainable products. PMID:24566040

Choi, Kwon-Young; Wernick, David G; Tat, Christine A; Liao, James C

2014-05-01

443

Dynamical percolation transition in the Ising model studied using a pulsed magnetic field  

NASA Astrophysics Data System (ADS)

We study the dynamical percolation transition of the geometrical clusters in the two-dimensional Ising model when it is subjected to a pulsed field below the critical temperature. The critical exponents are independent of the temperature and pulse width and are different from the (static) percolation transition associated with the thermal transition. For a different model that belongs to the Ising universality class, the exponents are found to be same, confirming that the behavior is a common feature of the Ising class. These observations, along with a universal critical Binder cumulant value, characterize the dynamical percolation of the Ising universality class.

Biswas, Soumyajyoti; Kundu, Anasuya; Chandra, Anjan Kumar

2011-02-01

444

Measuring ammonia concentration over a grassland near livestock facilities using a semiconductor ammonia sensor  

Microsoft Academic Search

We demonstrated the effectiveness of a semiconductor ammonia sensor capable of performing diachronic measurements; its characteristics were checked in the laboratory by means including comparison with standard gases. We found as a result that the ammonia sensor's readings increased with increasing water vapor pressure. We compared sensor readings with values obtained by chemical analysis of samples collected in situ and

S. Kawashima; S. Yonemura

2001-01-01

445

The importance of the ammonia purification process in ammonia–water absorption systems  

Microsoft Academic Search

Practical experience in working with ammonia–water absorption systems shows that the ammonia purification process is a crucial issue in order to obtain an efficient and reliable system. In this paper, the detrimental effects of the residual water content in the vapour refrigerant are described and quantified based on the system design variables that determine the effectiveness of the purification process.

José Fernández-Seara; Jaime Sieres

2006-01-01

446

Nitrogen recycling and nutritional provisioning by Blattabacterium, the cockroach endosymbiont.  

PubMed

Nitrogen acquisition and assimilation is a primary concern of insects feeding on diets largely composed of plant material. Reclaiming nitrogen from waste products provides a rich reserve for this limited resource, provided that recycling mechanisms are in place. Cockroaches, unlike most terrestrial insects, excrete waste nitrogen within their fat bodies as uric acids, postulated to be a supplement when dietary nitrogen is limited. The fat bodies of most cockroaches are inhabited by Blattabacterium, which are vertically transmitted, Gram-negative bacteria that have been hypothesized to participate in uric acid degradation, nitrogen assimilation, and nutrient provisioning. We have sequenced completely the Blattabacterium genome from Periplaneta americana. Genomic analysis confirms that Blattabacterium is a member of the Flavobacteriales (Bacteroidetes), with its closest known relative being the endosymbiont Sulcia muelleri, which is found in many sap-feeding insects. Metabolic reconstruction indicates that it lacks recognizable uricolytic enzymes, but it can recycle nitrogen from urea and ammonia, which are uric acid degradation products, into glutamate, using urease and glutamate dehydrogenase. Subsequently, Blattabacterium can produce all of the essential amino acids, various vitamins, and other required compounds from a limited palette of metabolic substrates. The ancient association with Blattabacterium has allowed cockroaches to subsist successfully on nitrogen-poor diets and to exploit nitrogenous wastes, capabilities that are critical to the ecological range and global distribution of cockroach species. PMID:19880743

Sabree, Zakee L; Kambhampati, Srinivas; Moran, Nancy A

2009-11-17

447

Nitrogen recycling and nutritional provisioning by Blattabacterium, the cockroach endosymbiont  

PubMed Central

Nitrogen acquisition and assimilation is a primary concern of insects feeding on diets largely composed of plant material. Reclaiming nitrogen from waste products provides a rich reserve for this limited resource, provided that recycling mechanisms are in place. Cockroaches, unlike most terrestrial insects, excrete waste nitrogen within their fat bodies as uric acids, postulated to be a supplement when dietary nitrogen is limited. The fat bodies of most cockroaches are inhabited by Blattabacterium, which are vertically transmitted, Gram-negative bacteria that have been hypothesized to participate in uric acid degradation, nitrogen assimilation, and nutrient provisioning. We have sequenced completely the Blattabacterium genome from Periplaneta americana. Genomic analysis confirms that Blattabacterium is a member of the Flavobacteriales (Bacteroidetes), with its closest known relative being the endosymbiont Sulcia muelleri, which is found in many sap-feeding insects. Metabolic reconstruction indicates that it lacks recognizable uricolytic enzymes, but it can recycle nitrogen from urea and ammonia, which are uric acid degradation products, into glutamate, using urease and glutamate dehydrogenase. Subsequently, Blattabacterium can produce all of the essential amino acids, various vitamins, and other required compounds from a limited palette of metabolic substrates. The ancient association with Blattabacterium has allowed cockroaches to subsist successfully on nitrogen-poor diets and to exploit nitrogenous wastes, capabilities that are critical to the ecological range and global distribution of cockroach species.

Sabree, Zakee L.; Kambhampati, Srinivas; Moran, Nancy A.

2009-01-01

448

National Center for Electronics Recycling  

NSDL National Science Digital Library

Used cellphones and laptops can't go in the recycling with the empty soda cans and cereal boxes. So where do they go to be recycled once consumers find new ones? The National Center for Electronics Recycling (NCER) is working on that very problem. Visitors can click on the "Ecycling Basics" tab on the left side of the page to be taken to links to three websites that allow you to search by zip code or an interactive map of the U.S. In the "Resources" tab on the left side of the page, there are many links to resources that include Advocacy Group Reports, Electronics Disposal Studies, Environmentally Sound Management Guidelines, and International documents. Visitors interested in keeping up with the news from NCER, can sign up for their newsletter in the Google groups box, which is located below the menu on the left side of the page.

449

Universal scaling of the formation factor in porous media derived by combining percolation and effective medium theories  

NASA Astrophysics Data System (ADS)

porosity dependence of the formation factor for geologic media is examined from the perspective of universal scaling laws from percolation and effective medium theories. Over much of the range of observed porosity, the expected percolation scaling is observed, but the values of the numerical prefactor do not conform to the simple predictions from percolation theory. Combining effective medium and percolation theories produces a numerical prefactor whose value depends on both the threshold porosity and the porosity above which the formation factor crosses from percolation to effective medium scaling. This change allows extraction of a numerical value of the prefactor, which is reasonably close to experimental values. Subsequent evaluation of the porosity dependence of the formation factor shows that difficulties in prior comparisons of theory and experiment are largely removed when percolation scaling is allowed to transition to effective medium scaling far above the percolation threshold.

Ghanbarian, Behzad; Hunt, Allen G.; Ewing, Robert P.; Skinner, Thomas E.

2014-06-01

450

Treatment of wastewater from a low-temperature carbonization process industry through biological and chemical oxidation processes for recycle/reuse: a case study.  

PubMed

Low-temperature carbonization (LTC) of coal generates highly complex wastewater warranting stringent treatment. Developing a techno-economically viable treatment facility for such wastewaters is a challenging task. The paper discusses a case study pertaining to an existing non-performing effluent treatment plant (ETP). The existing ETP comprising an ammonia stripper followed by a single stage biological oxidation was unable to treat 1,050 m(3)/d of effluent as per the stipulated discharge norms. The treated effluent from the existing ETP was characterized with high concentrations of ammonia (75-345 mg N/l), COD (313-1,422 mg/l) and cyanide (0.5-4 mg/l). Studies were undertaken to facilitate recycling/reuse of the treated effluent within the plant. A second stage biooxidation process was investigated at pilot scale for the treatment of the effluent from the ETP. This was further subjected to tertiary treatment with 0.5% dose of 4% hypochlorite which resulted in effluent with pH: 6.6-6.8, COD: 73-121 mg/l, and BOD(5):<10 mg/l. Phenol, cyanide and ammonia were below detectable limits and the colourless effluent was suitable for recycle and reuse. Thus, a modified treatment scheme comprising ammonia pre-stripping followed by two-stage biooxidation process and a chemical oxidation step with hypochlorite at tertiary stage was proposed for recycle/reuse of LTC wastewater. PMID:20453329

Biswas, R; Bagchi, S; Urewar, C; Gupta, D; Nandy, T

2010-01-01

451

Recycler short kicker beam impedance  

SciTech Connect

Measured longitudinal and calculated transverse beam impedance is presented for the short kicker magnets being installed in the Fermilab Recycler. Fermi drawing number ME-457159. The longitudinal impedance was measured with a stretched wire and the Panofsky equation was used to estimate the transverse impedance. The impedance of 3319 meters (the Recycler circumference) of stainless vacuum pipe is provided for comparison. Although measurements where done to 3GHz, impedance was negligible above 30MHz. The beam power lost to the kicker impedance is shown for a range of bunch lengths. The measurements are for one kicker assuming a rotation frequency of 90KHz. Seven of these kickers are being installed.

Crisp, Jim; Fellenz, Brian; /Fermilab

2009-07-01

452

Process to recycle shredder residue  

DOEpatents

A system and process for recycling shredder residue, in which separating any polyurethane foam materials are first separated. Then separate a fines fraction of less than about 1/4 inch leaving a plastics-rich fraction. Thereafter, the plastics rich fraction is sequentially contacted with a series of solvents beginning with one or more of hexane or an alcohol to remove automotive fluids; acetone to remove ABS; one or more of EDC, THF or a ketone having a boiling point of not greater than about 125.degree. C. to remove PVC; and one or more of xylene or toluene to remove polypropylene and polyethylene. The solvents are recovered and recycled.

Jody, Bassam J. (Chicago, IL); Daniels, Edward J. (Oak Lawn, IL); Bonsignore, Patrick V. (Channahon, IL)

2001-01-01

453

The Recycling Solution: How I Increased Recycling on Dilworth Road  

ERIC Educational Resources Information Center

The grandson of Fred Keller, one of the founders of behavior analysis, Jacob was 10 years old when he conducted the project for his elementary school science fair. We recently contacted Jacob to learn more about his project. He told us the inspiration came from a class field trip to the county recycling center, which included seeing video footage…

Keller, J. Jacob

2010-01-01

454

Configuration of recycling networks for enhanced WEEE recycling  

Microsoft Academic Search

Due to product heterogeneity and complexity disassembly of Waste Electrical and Electronic Equipment (WEEE) is seldom supported by systematic planning methods. In particular, uncertainties owing to almost unpredictable quantities and types of returned, products hamper anticipatory disassembly planning, which is mandatory to ensure efficient recycling. This paper introduces an integrated approach focussing on both intra-plant and inter-plant level optimization, underlying

E. Hesselbach; M. Ohlendorf; C. Herrmann

2001-01-01

455

Food Service Recycling: Whose Responsibility Is It?  

ERIC Educational Resources Information Center

The food service department at a Pennsylvania school district recycles polystyrene "styrofoam" cups, plates, and food trays. In addition, the department recycles glass, aluminum, and paper. Offers advice on how to set up a school program. (MLF)

Settanni, Barbara

1990-01-01

456

Converting Garbage to Gold: Recycling Our Materials.  

ERIC Educational Resources Information Center

Recycling conserves energy, fights pollution and inflation, creates jobs, and improves the outlook for the future of materials. But converting a throwaway society to recycling will depend on finding good markets for waste paper and scrap metals. (RM)

Chandler, William U.

1984-01-01

457

Minerals Yearbook, 1992: Recycling-Nonferrous Metals.  

National Technical Information Service (NTIS)

Because of the increasing importance of recycling to domestic metal supply and the intense public interest, the United States Bureau of Mines (USBM) initiated this separate chapter on nonferrous metal recycling as part of its Annual Report series in 1991....

J. F. Carlin D. Edelstein J. H. Jolly J. L. W. Jolly J. F. Papp

1994-01-01

458

The Ammonia?Hydrogen System under Pressure  

SciTech Connect

Binary mixtures of hydrogen and ammonia were compressed in diamond anvil cells to 15 GPa at room temperature over a range of compositions. The phase behavior was characterized using optical microscopy, Raman spectroscopy, and synchrotron X-ray diffraction. Below 1.2 GPa we observed two-phase coexistence between liquid ammonia and fluid hydrogen phases with limited solubility of hydrogen within the ammonia-rich phase. Complete immiscibility was observed subsequent to the freezing of ammonia phase III at 1.2 GPa, although hydrogen may become metastably trapped within the disordered face-centered-cubic lattice upon rapid solidification. For all compositions studied, the phase III to phase IV transition of ammonia occurred at {approx}3.8 GPa and hydrogen solidified at {approx}5.5 GPa, transition pressures equivalent to those observed for the pure components. A P-x phase diagram for the NH{sub 3}-H{sub 2} system is proposed on the basis of these observations with implications for planetary ices, molecular compound formation, and possible hydrogen storage materials.

Chidester, Bethany A.; Strobel, Timothy A. (CIW)

2012-01-20

459

40 CFR 261.6 - Requirements for recyclable materials.  

Code of Federal Regulations, 2013 CFR

...6(d).) (2) Owners or operators of facilities that recycle recyclable materials without storing them before they are recycled...permitting requirements with hazardous waste management units that recycle hazardous wastes are subject to the requirements of...

2013-07-01

460

Mechanical Stabilization of Earth Slopes Using Recycled Materials  

Microsoft Academic Search

Recycled materials are increasingly being used or considered for mechanical stabilization of abutments and earth slopes associated with transportation facilities. Specifically, recycled plastic lumber, recycled railroad rails, recycled guardrail posts, used railroad ties, \\

J. Erik Loehr; Thomas W. Fennessey; John J. Bowders

461

Percolation in polydisperse systems of aligned rods: A lattice-based analysis.  

PubMed

A model is developed for percolation in polydisperse systems of oriented cylinders that integrates excluded volume arguments with an analogy to site percolation on a modified Bethe lattice. Results from this treatment are presented for the volume fraction at the percolation threshold (denoted ?c) as a function of the degree of polydispersity, mixture composition, and degree of orientational ordering. For monodisperse systems, ?c is found to be a monotonically increasing function of the traditional orientational order parameter that quantifies degree of alignment. The presence of a fraction of isotropically oriented rods of small aspect ratio is shown to lower the percolation threshold for systems in which the longer rods are strongly aligned. PMID:24880329

Chatterjee, Avik P

2014-05-28

462

Complete set of types of phase transition in generalized heterogeneous k-core percolation  

NASA Astrophysics Data System (ADS)

We study heterogeneous k-core (HKC) percolation with a general mixture of the threshold k, with kmin=2 on random networks. Based on the local tree approximation, the scaling behaviors of the percolation order parameter P?(p) are analytically obtained for general distributions of the threshold k. The analytic calculations predict that the generalized HKC percolation is completely described by the series of continuous transitions with order parameter exponents ?n=2/n, discontinuous hybrid transitions with ?H=1/2 or ?A_4=1/4, and three kinds of multiple transitions. Simulations of the generalized HKC percolations are carried out to confirm analytically predicted transition natures. Specifically, the exponents of the series of continuous transitions are shown to satisfy the hyperscaling relation 2?n+?n=?¯n.

Chae, Huiseung; Yook, Soon-Hyung; Kim, Yup

2014-05-01

463

Localization-delocalization transitions in a two-dimensional quantum percolation model: von Neumann entropy studies  

NASA Astrophysics Data System (ADS)

In two-dimensional quantum site-percolation square lattice models, the von Neumann entropy is extensively studied numerically. At a certain eigenenergy, the localization-delocalization transition is reflected by the derivative of von Neumann entropy which is maximal at the quantum percolation threshold pq . The phase diagram of localization-delocalization transitions is deduced in the extrapolation to infinite system sizes. The nonmonotonic eigenenergies dependence of pq and the lowest value pq?0.665 are found. At localized-delocalized transition points, the finite scaling analysis for the von Neumann entropy is performed and it is found the critical exponents ? not to be universal. These studies provide an evidence that the existence of a quantum percolation threshold pq<1 in the two-dimensional quantum percolation problem.

Gong, Longyan; Tong, Peiqing

2009-11-01

464

Effect of Percolation on the Cubic Susceptibility of Metal Nanoparticle Composites  

NASA Technical Reports Server (NTRS)

Generalized two-dimensional and three-dimensional Maxwell Garnett and Bruggeman geometries reveal that a sign reversal in the cubic susceptibility occurs for metal nanoparticle composites near the percolation threshold.

Smith, David D.; Bender, Matthew W.; Boyd, Robert W.

1998-01-01

465

Economic and ecological costs and benefits of streamflow augmentation using recycled water in a California coastal stream.  

PubMed

Streamflow augmentation has the potential to become an important application of recycled water in water scarce areas. We assessed the economic and ecological merits of a recycled water project that opted for an inland release of tertiary-treated recycled water in a small stream and wetland compared to an ocean outfall discharge. Costs for the status-quo scenario of discharging secondary-treated effluent to the ocean were compared to those of the implemented scenario of inland streamflow augmentation using recycled water. The benefits of the inland-discharge scenario were greater than the increase in associated costs by US$1.8M, with recreational value and scenic amenity generating the greatest value. We also compared physical habitat quality, water quality, and benthic macroinvertebrate community upstream and downstream of the recycled water discharge to estimate the effect of streamflow augmentation on the ecosystem. The physical-habitat quality was higher downstream of the discharge, although streamflow came in unnatural diurnal pulses. Water quality remained relatively unchanged with respect to dissolved oxygen, pH, and ammonia-nitrogen, although temperatures were elevated. Benthic macroinvertebrates were present in higher abundances, although the diversity was relatively low. A federally listed species, the California red-legged frog (Rana draytonii), was present. Our results may support decision-making for wastewater treatment alternatives and recycled water applications in Mediterranean climates. PMID:23688175

Halaburka, Brian J; Lawrence, Justin E; Bischel, Heather N; Hsiao, Janet; Plumlee, Megan H; Resh, Vincent H; Luthy, Richard G

2013-10-01

466

Proceedings of the waste recycling workshop  

SciTech Connect

Recorded are seventeen talks from five sessions at the workshop. FERMCO`s recycling program, state of the art recycling technology, and an integrated demonstration of deactivation, decommissioning and decommissioning are presented in the plenary session. In the concrete session, decontamination and recycling are discussed. In the transite session, regulations are considered along with recycling and decontamination. In the metals session, radioactive scrap metals are emphasized. And in the regulatory considerations and liabilities session, DOE and EPA viewpoints are discussed. (GHH)

Bailey, R.E.; Thomas, A.F.; Ries, M.A. [eds.] [Ohio State Univ., Columbus, OH (United States)] [eds.; Ohio State Univ., Columbus, OH (United States)

1993-12-31

467

What Makes a Recycler?A Comparison of Recyclers and Nonrecyclers  

Microsoft Academic Search

Knowledge and motivational factors represent important but neglected topics in the study of recycling behavior. This article examines differences in knowledge, motives, and demographic characteristics of people who have the opportunity to recycle voluntarily. Information on these variables was obtained for 197 households in Illinois. The results indicated that recyclers in general were more aware of publicity about recycling and

Joanne Vining; Angela Ebreo

1990-01-01

468

Recycling at Penn State's Beaver Stadium. "Recycle on the Go" Success Story  

ERIC Educational Resources Information Center

With a 13-year-old recycling program, The Pennsylvania State University's (Penn State) Beaver Stadium in the past diverted nearly 30 tons of recyclables per year from local landfills. A new initiative to promote recycling in the stadium's tailgating area has helped Penn State more than triple its old recycling record, collecting 112 tons in 2008.…

US Environmental Protection Agency, 2009

2009-01-01

469

Heat Tracing Percolation in Managed Aquifer Recharge Facilities using Fiber Optic Distributed Temperature Sensing  

NASA Astrophysics Data System (ADS)

Percolation rates in Managed Aquifer Rechage (MAR) facilities, such as recharge basins and stream channels, can vary widely through both time and space. Natural variations in sediment hydraulic conductivity can create 'dead zones' in which percolation rates are negligible. Clogging is a constant problem, leading to decays in facility percolation rates . Measuring percolation rate variations is important for management, maintenance, and remediation of surface MAR facilities We have used Fiber Optic Distributed Temperature Sensing (FODTS) to monitor percolation in two very different recharge facilities. The first is a small (2 ha) nearly round recharge basin of homogeneous sediment type in which water balance can be closely monitored. The second is a long narrow river channel separated from an active river by a levee. The alluvial sediment in the river channel varies widely in texture and water balance is difficult to monitor independently. Both facilities were monitored by trenching in fiber optic cable and measuring the propagation rate of the diurnal temperature oscillations carried downward with infiltrating water. In this way, heat was used as a tracer of percolation rates along the section defined by the trenched cable (400 and 1600 m, respectively). We were able to confirm the FODTS measurements of percolation in the recharge basin and demonstrate its wide applicability in the river channel. Results from the measurements have been used to understand both the hydraulic behavior of percolation in the facilities and to make management decisions regarding facility operations and the potential need for additional surface sediment remediation. Estimation of specific discharge (m/day) through the basin using the wavelet method. Basin stage is shown above

Becker, M.; Ellis, W.; Bauer, B.; Hutchinson, A.

2013-12-01

470

Voltage percolation thresholds evidenced in the electrical behaviour of different nanostructures  

Microsoft Academic Search

Percolation phenomena are investigated and discussed in three kinds of nanostructures: first two are nanocrystalline silicon-based systems, Si nanodots embedded in amorphous SiO2 matrix and porous silicon formed by an oxidized nanowire network, and the third consisting of a multi-walled carbon nanotube network embedded in amorphous SiN. The current-voltage characteristics measured on first two systems present voltage percolation thresholds with

I. Stavarache

2011-01-01

471

Note: optimization of the numerical data analysis for conductivity percolation studies of drying moist porous systems.  

PubMed

A simplified data analysis protocol, for dielectric spectroscopy use to study conductivity percolation in dehydrating granular media is discussed. To enhance visibility of the protonic conductivity contribution to the dielectric loss spectrum, detrimental effects of either low-frequency dielectric relaxation or electrode polarization are removed. Use of the directly measurable monofrequency dielectric loss factor rather than estimated DC conductivity to parameterize the percolation transition substantially reduces the analysis work and time. PMID:24593402

Moscicki, J K; Sokolowska, D; Kwiatkowski, L; Dziob, D; Nowak, J

2014-02-01

472

Percolation-like approach to resistivity behaviour of glassforming ionic melts  

Microsoft Academic Search

The Vogel–Fulcher equation (and percolation approach) predicts an infinite resistivity below the “ideal” glassification point T0 (correspondingly- percolation threshold). However, the ions still preserve a noticeable mobility within the real glasses even below T0. To model the finite resistivity in glass a resistance Rmax of a broken bond is introduced. The ratio of Rmax\\/Rmin in real glasses is about 1014

V. Sh Machavariani; A Voronel

1999-01-01

473

Modeling of Aqueous Transport in Rigid Porous Matrices near the Percolation Threshold  

Microsoft Academic Search

Purpose  To demonstrate control of passive diffusion of small molecules through rigid ceramic matrices via manipulation of matrix porosity near the percolation threshold, and to model such control using percolation scaling relationships on both infinite and finite lattices.Materials and Methods  Rigid alumina disks of controlled porosity were prepared using standard ceramic casting and sintering techniques. Structural void space distributions in sintered disks

Scott R. Ellis; James L. Wright

2006-01-01

474

Percolation model for elastic softening in intermetallic compounds during solid-state amorphization  

NASA Astrophysics Data System (ADS)

By using isobaric-isothermal molecular dynamics and an n-body effective potential, we show that the amorphization of NiZr2, mediated by chemical disorder, is preceded by an elastic softening and begins at the percolation threshold of the strain distortion regions associated with the antisite defects. The percolation model provides a unified description of the elastic softening and loss of crystalline order in intermetallic compounds resulting from irradiation or hydrogenation.

Massobrio, C.; Pontikis, V.

1992-02-01