Carbon nanotube growth density control

Method and system for combined coarse scale control and fine scale control of growth density of a carbon nanotube (CNT) array on a substrate, using a selected electrical field adjacent to a substrate surface for coarse scale density control (by one or more orders of magnitude) and a selected CNT growth temperature range for fine scale density control (by multiplicative factors of less than an order of magnitude) of CNT growth density. Two spaced apart regions on a substrate may have different CNT growth densities and/or may use different feed gases for CNT growth

Control of Carbon Nanotube Density and Tower Height in an Array

A method for controlling density or tower height of carbon nanotube (CNT) arrays grown in spaced apart first and second regions on a substrate. CNTs having a first density range (or first tower height range) are grown in the first region using a first source temperature range for growth. Subsequently or simultaneously, CNTs having a second density range (or second tower height range), having an average density (or average tower height) in the second region different from the average density (or average tower height) for the first region, are grown in the second region, using supplemental localized hearing for the second region. Application for thermal dissipation and/or dissipation of electrical charge or voltage in an electronic device are discussed

Robuustheid in een samengesteld mobiliteitssysteem; over tijdelijke optima en gelaagde bestuurskundige uitdagingen

Zowel in mobiliteitsonderzoek als in de beleidspraktijk valt er recentelijk een onmiskenbaar streven naar 'robuustheid' waar te nemen. Dit streven is vaak een reactie op een als zeer dynamisch ervaren omgeving. Het is daarbij echter opvallend dat er zeer uiteenlopende invullingen aan dit concept worden gegeven. Dit roept de vraag op of het concept ‘robuustheid’ wel van toegevoegde waarde is voor het bestuur in het mobiliteitsdomein. Maar vooral roept het de vraag op hoe het dat kan zijn. In deze bijdrage wordt geredeneerd vanuit de complexiteit van een samengesteld mobiliteitssysteem: De gehanteerde premisse is dat pogingen om mobiliteit te sturen of te beïnvloeden plaatsvinden in dynamische en slechts deels controleerbare omgevingen. Het streven naar robuustheid is zo beschouwd dus begrijpelijk, maar ook inherent moeizaam. De centrale vraag die moet worden beantwoord is: “Hoe kan het concept ‘robuustheid’ helpen richting te geven aan het handelen in een samengesteld, gelaagd en padafhankelijk mobiliteitssysteem?” De vraag wordt beantwoord vanuit een theoretische reflectie op de verschillende verschijningsvormen en interpretaties van ‘robuustheid’. Vanuit onze empirie (in zowel weg, water als rail) komt dan naar voren dat robuustheid soms meer en soms minder dynamisch wordt ingevuld, dat soms fysieke, soms juist sociale dimensies worden benadrukt, en dat het onder uiteenlopende randvoorwaarden wordt vormgegeven. Daarbij valt ook op dat robuustheid in deelsystemen niet altijd tot algehele robuustheid leidt, en vaak deeloplossingen biedt. Sterker nog, in de meer omvattende analyses van het mobiliteitssysteem is de systemische robuustheid eerder deel van het probleem dan de oplossing. Op ‘robuustheid’ gericht mobiliteitsbeleid betreft gewoonlijk het managen van deelsystemen. Deze doorgaans lokale en tijdelijke robuustheid zal bijsturing, onderhoud en aanpassing vergen. Maar daarbij zal ook beseft moeten worden dat deze robuustheid gelijktijdig weer deel uitmaakt van een gelaagd, vervlochten en in sommige opzichten ook wel hardnekkig mobiliteitssysteem

Friction and Contact Temperatures in the Cleaving of Bone and Wood Using Stone Tools – A Case Study in Palaeolithic Tribology

During archaeological fieldwork wedge-shaped quartz stones that show clearly visible “glossy patches” composed of high quartz have been found. It is generally accepted that these tools have been used to cleave or punch wood and bone materials. For the transformation from quartz to high-quartz to occur, the temperature should exceed 574 °C. The hypothesis tested in this manuscript is that the phase change in the stone tool results from frictional heating during the cleaving action. Dry sliding friction measurements were carried out on a reciprocating tribometer using four types of stone, representing the punch tool, and pine, oak and bovine bone, representing the work piece. Measured coefficients of friction were approximately 0.1 on oak, 0.2 on pine and up to 0.35 on bovine bone, with some minor fluctuations for the different types of stone. These coefficients of friction were inserted into a computational model describing the flash temperatures in a moving contact, from which it was shown that the hypothesis might hold in the case of lydite-bone contact. This means that the glossy patches on the stone tools may have been caused by frictional heating during the cleaving of bone.</p

Stick-slip behaviour of a viscoelastic flat sliding along a rigid indenter

The sliding contact of soft material surface due to a rigid indenter is different from metal and some other polymers. A stick-slip motion is more frequently obtained than a smooth motion. By modeling the soft material as low damping viscoelastic material, this study proposes an analytical model to identify the stick-slip behavior of sliding system. The sliding system is a fixed rigid indenter that slides against on a moving soft material surface. A stick-slip model is developed and the motion of the sliding system is assumed to be in a solely tangential direction. By implementing the simple coulomb friction law, an exact solution is presented in the case of no damping of the sliding system. Results show that the periodic displacement of the stick-slip model is strongly depending on the friction force, sliding velocity and material stiffness. Furthermore, the effect of a viscous damping and velocity-dependent friction on the behaviour of the sliding system are discussed

The Axis-Ratio Distribution of Galaxy Clusters in the SDSS-C4 Catalog as a New Cosmological Probe

We analyze the C4 catalog of galaxy clusters from the Sloan Digital Sky Survey (SDSS) to investigate the axis-ratio distribution of the projected two dimensional cluster profiles. We consider only those objects in the catalog whose virial mass is close to 10^{14}h^{-1}M_{sun}, with member galaxies within the scale radius 1000 kpc. The total number of such objects turns out to be 336. We also derive a theoretical distribution by incorporating the effect of projection onto the sky into the analytic formalism proposed recently by Lee, Jing, & Suto. The theoretical distribution of the cluster axis-ratios is shown to depend on the amplitude of the linear power spectrum (sigma_8) as well as the density parameter (Omega_{m}). Finally, fitting the observational data to the analytic distribution with Omega_{m} and sigma_{8} as two adjustable free parameters, we find the best-fitting value of sigma_{8}=(1.01 +/- 0.09)(Omega_{m}/0.6)^{(0.07 +/- 0.02) +0.1 Omega_{m}}$. It is a new sigma_{8}-Omega_{m} relation, different from the previous one derived from the local abundance of X-ray clusters. We expect that the axis-ratio distribution of galaxy clusters, if combined with the local abundance of clusters, may put simultaneous constraints on sigma_{8} and Omega_{m}.Comment: accepted for publication in ApJ, 17 pages, 3 figures, improved analysis, more discussion on the validity and the caveats of the mode

A Knowledge-based Clinical Toxicology Consultant for Diagnosing Multiple Exposures

Objective: This paper presents continued research toward the development of a knowledge-based system for the diagnosis of human toxic exposures. In particular, this research focuses on the challenging task of diagnosing exposures to multiple toxins. Although only 10% of toxic exposures in the United States involve multiple toxins, multiple exposures account for more than half of all toxin-related fatalities. Using simple medical mathematics, we seek to produce a practical decision support system capable of supplying useful information to aid in the diagnosis of complex cases involving multiple unknown substances. Methods: The system is automatically trained using data mining techniques to extract prior probabilities and likelihood ratios from a database managed by the Florida Poison Information Center (FPIC). When supplied with observed clinical effects, the system produces a ranked list of the most plausible toxic exposures. During testing, the system diagnosed toxins at three levels: identifying the substance, identifying the toxin’s major and minor categories, and identifying the toxin’s major category alone. To enable comparison between these three levels, accuracy was calculated as the percentage of exposures correctly identified in top 10% of trained diagnoses. Results: System evaluation utilized a dataset of 8,901 multiple exposure cases and 37,617 single exposure cases. Initial system testing using only multiple exposure cases yielded poor results, with diagnosis accuracies ranging from 18.5-50.1%. Further investigation revealed that the system’s inability to diagnose multiple disorders resulted from insufficient data and that the clinical effects observed in multiple exposures are dominated by a single substance. Including single exposures when training, the system achieved accuracies as high as 83.5% when 2 diagnosing the primary contributors in multiple exposure cases by substance, 86.9% when diagnosing by major and minor categories, and 79.9% when diagnosing by major category alone. Conclusions: Although the system failed to completely diagnose exposures to multiple toxins, the ability to identify the primary contributor in such cases may prove valuable in aiding medical personnel as they seek to diagnose and treat patients. As time passes and more cases are added to the FPIC database, we believe system accuracy will continue to improve, producing a viable decision support system for clinical toxicology