186,577 research outputs found
Some measurements of surface drag in urban-type boundary layers at various wind angles
No full textUsing experimental data obtained in naturally grown boundary layers over a generic urban-type roughness (height h) it is shown that the surface drag is strongly dependent on the flow direction with respect to the roughness orientation. The variations with wind direction are accompanied by corresponding changes in the parameters contained in the usual logarithmic description of the flow in the near-wall inertial layer, U/u?=1?ln[(z?d)/zo] , principally the roughness length z o, which can vary by a factor of around three. The maximum surface drag (and roughness length) occur when the flow direction is at an angle around 45° to the faces of the cubical roughness elements, consistent with the known fact that the drag of an isolated cube in a thick boundary layer is much larger at that orientation than for flow directions normal to the faces. An accurate electronic balance was used to determine the surface drag (and hence friction velocity u ? ) and pressure-tapped roughness elements allowed estimation of the zero plane displacement d. It is shown that the best logarithmic-law fits then generally require values of the von Kármán ‘constant’ ? significantly lower than its classical value of around 0.41. For a factor of six increase in the Reynolds number (from Urefh/??3,500 ), Reynolds number effects are shown to be very weak and, coupled with the form drag and total drag data, the results thus suggest that frictional contributions to the total surface drag are relatively smal
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Edward P. Wimberly, ITC, July 2011
No full textThis video is a conversation with Dr. Edward P. Wimberly. Dr. Wimberly talks about his book, "No Shame in Wesley's Gospel: A Twenty-First Century Pastoral Gospel". Brad Ost, AUC Woodruff Library, is the interviewer
Author Rights and Scholarly Publishing
No full textOriginally posted at
http://blog.library.gsu.edu/2014/10/24/author-rights-and-scholarly-publishing/</p
Phosphorus from sludge : evaluation of organic polymer substitution of metal coagulants on phosphorus availability for plant uptake
No full textMajority of Norwegian wastewater treatment plants utilize chemical treatments such as coagulation to meet high removal standards for phosphorus in wastewater. Up to 85% of the total sludge produced from these plants are supplied to farmers for use for possibility of reuse of nutrients, such as P, in agriculture. A study done by Tore Krogstad found that the plant availability of phosphorus from sludge is greatly reduced along with higher concentrations of metal coagulants. To enable wastewater treatment plants to continue meeting high removal efficiency while providing sludge with better P fertilizing capacity, some researches have suggested the substitution a part of the inorganic coagulants with cationic polymers.
In this study, varying combinations of dose and polymer additions with commonly used coagulants ALS and PAX are evaluated on their effective plant available phosphorus when applied to soil and hydroponics systems as fertilizer. Despite improving removal of total phosphorus from wastewater, the simultaneous addition of cationic polyacrylamide to metal salts in coagulation reduced dry mass harvest, most particularly from ALS, with yield reduction documented from 57.5% to 66.1%. Addition of polymers to PAX had a smaller harvest drop ranging from 0.8% to 27%. As compared to mineral fertilizers, nutrient use efficiencies at input P concentration of 6 kg P/daa of the different sludge types were all under 40%, going as low as 6% for ALS + polymer sludge.
Reduction of the yield could be attributed to residual positive charge from the polymer used in the sludge could that may have fixed negatively charged phosphates in the soil, the phytotoxic effect cationic polymers or the mobilization of Al in soil for plant uptake. Further studies are needed to point out the actual mechanism by which the positively-charged polymers inhibit plant growth.
Use of hydroponic growth systems generally reflected soil conditions in terms of plant mass harvest in response to the different sludge types. Yet, evaluations through soil growth were found necessary to address soil interactions not simulated in the hydroponics system such as effect on nutrient uptake
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