1522 research outputs found
Sort by
Generalized Narayana Polynomials, Riordan Arrays and Lattice Paths
Get PDFWe study a family of polynomials in two variables, identifying them as the moments of a two-parameter family of orthogonal polynomials. The coefficient array of these orthogonal polynomials is shown to be an ordinary Riordan array. We express the generating function of the sequence of polynomials under study as a continued fraction, and determine the corresponding Hankel transform. An alternative characterization of the polynomials in terms of a related Riordan array is also given. This Riordan array is associated with Lukasiewicz paths. The special form of the production matrices is exhibited in both cases. This allows us to produce a bijection from a set of coloured Lukasiewicz paths to a set of coloured Motzkin paths. The polynomials studied generalize the notion of Narayana polynomial
Four-term recurrences, orthogonal polynomials and Riordan arrays
Get PDFWe study constant coefficient four term recurrences for polynomials, in analogy to the three-term recurrences that are associated with orthogonal polynomials. We show that for a family of polynomials obeying such a four-term recurrence, the coefficient array is an ordinary Riordan array of a special type, and vice versa. In certain cases, it is possible to transform these polynomials into related orthogonal polynomials. We characterize the form of the production matrices of the inverse coefficient arrays
An evaluation of wood fuel production parameters from Irish Sitka spruce first thinnings
Get PDFA comprehensive study of a number of in-forest wood energy supply chains was undertaken to collect empirical data on many aspects of both the stand and operational parameters therein. The data was then used to develop statistical models, so that a number of harvesting systems could be compared in a simulated environment. The simulated environment had two factors: the mean diameter at breast height (dbh) of the stand (cm), and the mean extraction distance (m). The harvesting systems compared were: cut to length (CTL) harvesting, CTL harvesting with chipping of the pulp assortment, and whole tree harvesting with terrain chipping of the whole trees. Not only were models developed on the productivity of the machines, but a taper equation, dbh to total height model, and a set of dbh distribution models were developed to predict the volumes of the assortments attributable to each harvesting system down to the tree level. The productivity models then used this data to estimate a cost of production per hectare for the harvesting systems. A value per unit volume of the assortments was taken from literature, and a profit analysis performed for each harvesting system. The simulation results show that whole tree harvesting and terrain chipping returns the highest positive profit for all levels of mean dbh at short extraction distances, but suffered from the machine interaction in the terrain chipping system at long extraction distances. The machine interaction between the terrain chipper and the chips forwarder was analysed using discrete event simulations. CTL harvesting and chipping of the pulp assortment returned the highest positive profit at longer extraction distances
Personality, Motivation and Level of Involvement of Land-Based Recreationists in the Irish Uplands
Get PDFThis research examined the influence of personality traits and motivational factors for participation in land based recreation in the Irish uplands. During the Summer and Autumn months of 2011 a total of 460 (males; n=268, females; n=192) onsite upland recreationists completed a survey instrument designed to assess their; motivations for participation, personality traits, level of involvement and perceived identity levels for their activity. The results identified that Hill Walking is the most popular land based activity undertaken in the Irish uplands (41% of all recreationists). There was no difference (p=0.331) or relationship (r=0.046) between the personality traits of the recreationists and their choice of upland activity. The main reason cited for participation was to be in Nature/Environment (mean 12.27, ±SD 2.58), while Mountaineers were the most motivated recreationists (mean 83.70 ±SD 9.64) and had the greatest level of involvement (mean 21.40 ±SD 2.63) with their activity. There was no difference or relationship found between perceived identity and activity (p=0.188, r=-0.029), personality (p=0.412, r=0.033), motivation (p=0.078, r=-0.87) or level of involvement (p=0.121, r=-0.074). The results from this study can have useful implications for policy makers in the fields of health and tourism, park managers, researchers and those in the retail and tourism industry who are interested in providing products and services for upland recreationists in Ireland
Reflective Writing: Quantitative Assessment and Identification of Linguistic Features
Get PDFReflective writing is used in higher education to encourage students to reflect on their learning or practice; in this context, reflective writing is frequently assessed. However, not enough is known about the criteria that educators use when assessing reflection. Many studies have developed rubrics for reflective writing assessment but these instruments are based on broad qualitative criteria and make no attempt to quantify depth of reflection. In addition to this, little is known about the linguistic structure of reflective writing; although some recent studies have examined its features, these characteristics have not been correlated to levels of reflective depth. Also of concern are the ways in which technology can impact the reflective writing and assessment process. Although many studies tout the benefits of using reflective blogging in higher education there is a dearth of empirical data that compares the effectiveness of blogging with more traditional ‘offline’ journals. A Delphi study was conducted with a group of international Reflective Practice experts to determine the criteria they use to assess reflective writing. The first round of the study identified 12 indicators of reflection; in the second round experts ranked these indicators according to depth of reflection. The reflection indicators form the basis of an instrument that can be used to assign a quantitative score to a piece of reflective writing based on the depth of reflection it contains. This instrument was used to perform a content analysis on the academic reflective writing contained in 27 reflective blogs and journals. The linguistic resources used in students’ writing were also assessed. A strong correlation was found between the overall reflective score and the total number of linguistic resources used, showing that reflective writing tends to be linguistically richer. In addition to this, relationships were seen between specific features of reflective writing and levels of reflection. A reflective scoresheet was developed that maps reflective writing assessment criteria to expected linguistic resources. This new understanding of the structure of reflective writing also has implications for the fields of automated writing evaluation and intelligent tutoring. The study also compared the writing in blogs and journals and found no significant difference in the linguistic resources they utilised, showing that the type of language used is the same, regardless of medium. A correlation was seen between the provision of feedback and improvement in reflective writing over time. A model of the reflective writing and assessment process that describes how blogs can be used to support the provision of regular formative feedback was presented
Introduction to EndNote - A WIT Libraries Tutorial: Digital Learning Resources for EndNote; a bibliographic software package
No full textEndNote is the standard bibliographic management tool used by staff and students in Waterford Institute of Technology (WIT). The project team wanted to develop an online interactive tutorial for the teaching of EndNote to provide a self-directed flexible tool that students and staff could access at their convenience. Prior to this tutorial, EndNote instruction had been solely provided by in-class training. The creation of the tutorial also contributes to institutional learning and teaching strategies in up-skilling the WIT community in bibliographic instruction and use of bibliographic software
Investigation of the role of HMGB2 in endocrine resistant breast cancer
Get PDFThe high mobility group box 2 protein (HMGB2) is an abundant chromatin remodelling
protein with an affinity for unusual DNA structures. It induces architectural
modifications to DNA structure, thereby allowing easier access for transcriptional
machinery to promoters of interest. Immunohistochemical staining of our patient tissue
microarray revealed that patients who are positive for HMGB2 in their primary tumour
have a reduced risk of breast cancer recurrence. This favourable outcome could be due
to the interaction between the estrogen receptor α (ERα) and HMGB2, as ERα positive
tumours promote the formation of a luminal type tumour, which are less aggressive in
general. HMGB2 was identified as a steroid receptor coactivator 1 (SRC1) binding
partner in an endocrine resistant cell model, but not the endocrine sensitive model. In
contrast to HMGB2, SRC1 has previously been associated with a reduced disease free
survival. It is possible that the role of HMGB2 changes as the tumour develops
resistance to an endocrine therapy. This study demonstrates that HMGB2 increases the
interaction between ERα and SRC1 in an endocrine resistance breast cancer cell line.
We have shown that HMGB2 binds to the estrogen regulated breast cancer amplified
sequence 3 (BCAS3) promoter in an endocrine resistant cell line. Furthermore, estrogen
and tamoxifen treatment increase this level of binding. HMGB2 has also been shown to
regulate protein expression of BCAS3 in endocrine resistance. A knock-down study of
HMGB2 resulted in a decreased expression of BCAS3. Conversely, over-expressing
HMGB2 resulted in increase in BCAS3 protein expression. The findings in this study
suggest that a transcriptional complex of SRC1/ERα/HMGB2 regulate the
transcriptional activity of BCAS3 in endocrine resistant breast cancer
Distributed formal concept analysis algorithms based on an iterative mapreduce framework
Get PDFWhile many existing formal concept analysis algorithms are
efficient, they are typically unsuitable for distributed implementation.
Taking the MapReduce (MR) framework as our inspiration we introduce
a distributed approach for performing formal concept mining. Our
method has its novelty in that we use a light-weight MapReduce runtime called Twister which is better suited to iterative algorithms than recent distributed approaches. First, we describe the theoretical foundations underpinning our distributed formal concept analysis approach. Second, we provide a representative exemplar of how a classic centralized algorithm can be implemented in a distributed fashion using our methodology: we modify Ganter’s classic algorithm by introducing a family of MR⋆ algorithms, namely MRGanter and MRGanter+ where the prefix denotes the algorithm’s lineage. To evaluate the factors that impact distributed algorithm performance, we compare our MR� algorithms with the state-of-the-art. Experiments conducted on real datasets demonstrate that MRGanter+ is efficient, scalable and an appealing algorithm for distributed problems
Spatial Profiling of Quantum Dot Lasers
Get PDFThe unique electronic structure of quantum dot based semiconductor lasers
leads to significant differences in lasing properties when compared to their quantum
well counterparts. In particular, the total injected carrier population can
be separated into two types: one that take part in lasing process, called resonant
charge carriers and the other one that do not take part in lasing process, called nonresonant
charge carriers. In this thesis, two methods are used to model injection
profiled quantum dot lasers and examine the roles of resonant and non-resonant
carrier populations.
The first model is a rate equation approach, which is used to analyze the
dynamical properties along the transverse section of the laser. The second model
is a steady state beam propagation approach, which calculates both transverse
and longitudinal carrier and field distributions in the laser. Numerical simulations
on both models reveal the role of non-resonant carries in the appearance of a
characteristic dip at the center of the near field intensity profile. Furthermore,
these models reveal the occurrence of symmetry breaking in the near and far field
intensity distributions at high injection currents. In addition, the steady state
beam propagation approach uncovers non-uniformities in the non-resonant carrier
profile along the longitudinal dimension.
In addition to single emitters, this work also examines the possibility of
phase-locking between two transversely coupled injection profiled QD lasers, where
various types of phase relationships are identified. We compare the performance
of single and double emitters by examining the beam focusing properties and evaluating
M2 factor for various configurations