130,609 research outputs found
Near-Optimal Feedback Guidance for Low-Thrust Earth Orbit Transfers
No full textThis research proposes a near-optimal feedback guidance based on nonlinear control for low-thrust Earth orbit transfers. For the numerical simulations, two flight conditions are defined: (i) nominal conditions and (ii) nonnominal conditions that account for the orbit injection errors and the stochastic failures of the propulsion system. Condition (ii) is studied through an extensive Monte Carlo Analysis, to demonstrate the nonlinear feedback guidance’s numerical stability andconvergence properties. To illustrate the performance under both conditions, an orbit transfer from low Earth orbit to geostationary orbit is considered. Near-optimality of the feedback guidance comes from carefully selecting the nonlinear control gains. Comparison of the transfer with an existing study that uses optimal control reveals that orbit transfers based on feedback orbit control are very close to the optimal solution.Control & Simulatio
The assessment of ground engineering properties of soils in the natural drainage network in the coastal line of Tekirdag central district
No full textWOS: 000453168600006In this study, physical and the ground engineering properties of the soil samples, taken from streambeds in the drainage network systems in the coastal line of Tekirdag, Central district have been specified. The soils, subject to the research are generally in a clay texture class and have a low hydraulic conductivity. The liquid limit (LL) values of the soils vary between 28.30% and 68.15%, plastic limit (PL) values - between 11.44% and 34.94%, and plasticity index (PI) values - between 14.64% and 34.53%. Regarding clay activity, they are in the "non-active" class. According to the Casagrande plasticity card; the soils have been classified to be moderate plastic inorganic clays, too much plastic inorganic clays, too much compressible inorganic silts and organic clays and non-cohesive soils. According to the AASHO classification system, soil samples enter into the A-6 group, A-7-5 and A-7-6 subgroups. Groups of soils for the USCS system have been found as CL, CH, MH or OH and SC. Terraces, formed by the drainage network systems, hillsides and alluvial lands are suitable for agriculture, for other usages should be considered according to the purposes of the use
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Properties of soils in some streambeds in Tekirdag central district
No full textBu çal ma, akarsu yataklar ndaki topraklar için bir veri taban olu turmak amac yla yap lm t r. Buamaçla Tekirda Merkez ilçesindeki baz akarsu yataklar ndaki arazilerin fiziksel ve kimyasal özellikleribelirlenmi tir. Ara t rma alan nda incelenen drenaj a sistemleri, birbirlerine paralel ve denize dik ve yar paralel (subparalel) drenaj a sistemleridir. Akarsu yataklar ndan yüzey topra olarak al nan örneklerde;tekstür, pH, tuz, kireç, organik madde, hidrolik iletkenlik ve baz makro ve mikro element analizleriyap lm t r. Yap lan de erlendirmeler sonucunda, pH de erleri genellikle nötr olarak bulunan yüzeytopraklar nda tuzluluk sorununa rastlanmam t r. Yüzey topraklar n n kireç ve organik madde kapsamlar genellikle az olarak saptan rken, demir, bak r ve mangan n yeterli oldu u bulunmu tur. Fakat çinkonoksanl tespit edilmi tir. Toprak örneklerinin yaray l fosfor ve de i ebilir potasyum içerikleri genellikleyeterlidir. Topraklar n büyük bir k sm kil tekstür s n f nda oldu u için yava hidrolik iletkenli e sahiptirler.Topraklar n mevcut fiziksel ve kimyasal özelliklerinin korunmas ve eksik yönlerinin iyile tirilmesi için ba taah r gübresi olmak üzere di er gübreler kullan lmal d r. Toprak i leme, sulama gibi di er tar msaluygulamalar için gerekli önlemler al nmal d rThis study was made in order to create a database for soils in streambeds. For this purpose, physicaland chemical properties of lands in some streambeds in Tekirdag Central district have been specified.The drainage network systems, examined at the research area, are drainage network systems that areparallel to one another and that are vertical and semi-parallel (sub-parallel) to the sea. In samples takenfrom streambeds as the surface soil; texture, pH, salt, lime, organic matter, hydraulic conductivity analysesand some macro and micro element analyses were made. As a result of the assessments made, therewas no saltiness problem encountered in the surface soils and their pH values have been found to begenerally neutral. While the lime and organic matter scopes of the surface soils have been determinedto be generally small, iron, copper and manganese have been found sufficient. But zinc deficiency hasbeen identified. Available phosphorus and exchangeable potassium contents of soil samples are generallysufficient. Because the majority of soils are in a clay texture class have a slow hydraulic conductivity.Other fertilizers should be used, especially barnyard manure for improving of disadvantages andprotection of current physical and chemical properties of soils. Necessary measures must be taken forthe other agricultural applications as tillage, irrigatio
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
New histone deacetylase inhibitors as potential therapeutic tools for advanced prostate carcinoma
No full textThe anti-epileptic drug valproic acid is also under trial as an anti-cancer agent due to its histone deacetylase (HDAC) inhibitory properties. However, the effects of valproic acid (VPA) are limited and concentrations required for exerting anti-neoplastic effects in vitro may not be reached in tumour patients. In this study, we tested in vitro and in vivo effects of two VPA-derivatives (ACS2, ACS33) on pre-clinical prostate cancer models. PC3 and DU-145 prostate tumour cell lines were treated with various concentrations of ACS2 or ACS33 to perform in vitro cell proliferation 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and to evaluate tumour cell adhesion to endothelial cell monolayers. Analysis of acetylated histones H3 and H4 protein expression was performed by western blotting. In vivo tumour growth was conducted in subcutaneous xenograft mouse models. Tumour sections were assessed by immunohistochemistry for histone H3 acetylation and proliferation. ACS2 and ACS33 significantly up-regulated histone H3 and H4 acetylation in prostate cancer cell lines. In micromolar concentrations both compounds exerted growth arrest in PC3 and DU-145 cells and prevented tumour cell attachment to endothelium. In vivo, ACS33 inhibited the growth of PC3 in subcutaneous xenografts. Immunohistochemistry and western blotting confirmed increased histone H3 acetylation and reduced proliferation. ACS2 and ACS33 represent novel VPA derivatives with superior anti-tumoural activities, compared to the mother compound. This investigation lends support to the clinical testing of ACS2 or ACS33 for the treatment of prostate cancer
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
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