scholarly journals Πολυκριτηριακή ανάλυση με χρήση της μεθόδου VIKOR σε αρδευτικά δίκτυα της πεδιάδας Θεσσαλονίκης

2014 ◽  
Author(s):  
Δήμητρα Ζορμπά
Keyword(s):  
Maximum Group

O σκοπός της παρούσας διδακτορικής διατριβής υπήρξε η επιλογή του βέλτιστου αρδευτικού δικτύου στην πεδιάδα της Θεσσαλονίκης μεταξύ μιας ομάδας αρδευτικών δικτύων, τα οποία επιλέχθηκαν προκειμένου να ενσωματωθούν στον οικονομικό χρονικό προγραμματισμό του ΓΟΕΒ Θεσσαλονίκης – Λαγκαδά. Ως βέλτιστο αρδευτικό δίκτυο θεωρήθηκε εκείνο το δίκτυο της ομάδας που ικανοποιούσε όσο ήταν δυνατόν περισσότερα κριτήρια από μια ομάδα κριτηρίων. Η ομάδα των αρδευτικών δικτύων αποτελούσε τις εναλλακτικές δραστηριότητες ή προτάσεις και επομένως κάθε εναλλακτική πρόταση βαθμολογήθηκε σε σχέση με τα κριτήρια αυτά. Για την λύση του πολύπλοκου αυτού προβλήματος, επιλέχθηκε η θεωρία της πολυκριτηριακής ανάλυσης και ειδικότερα η μέθοδος VIKOR που είναι μια εκ των τεσσάρων μεθόδων που περιλαμβάνονται στις συμβιβαστικές μεθόδους. Η μέθοδος VIKOR αναπτύχθηκε από τον Opricovic στο Πολυτεχνείο του Βελιγραδίου και βασίζεται στις L1 και L∞ νόρμες, με εισαγωγή μιας ενδιάμεσης Q νόρμας ως γραμμικού συνδυασμού των L1 και L∞. Η συμβιβαστική λύση που απορρέει, παρέχει μια μέγιστη ωφέλεια του συνόλου της «πλειοψηφίας» (maximum group utility of majority) και μια ελάχιστη ατομική διαφορά του «αντιπάλου» (minimum individual regret of the opponent). Στην παρούσα διατριβή εφαρμόστηκε για την βαθμονόμηση τόσο των αρδευτικών δικτύων (εναλλακτικές προτάσεις) όσο και των βαρών η μέθοδος Α.Η.Ρ.. Με τον τρόπο αυτό αντικειμενικοποιήθηκαν κατά το δυνατόν τα κριτήρια και τα σταθμιστικά βάρη. Στο τέλος των υπολογισμών προκύπτει μια ιεράρχηση αποστάσεων ως προς το ιδανικό σημείο, και επομένως εκείνο το αρδευτικό δίκτυο που έχει την μικρότερη απόσταση από το ιδανικό σημείο, θεωρείται ως το ιδανικό αρδευτικό δίκτυο, και έπονται ιεραρχικά τα υπόλοιπα. Η περιοχή μελέτης είναι σχεδόν όλη η πεδιάδα Θεσσαλονίκης. Συγκεκριμένα μελετήθηκαν 24 αρδευτικά δίκτυα. Τα αρδευτικά δίκτυα που σχηματίζουν την Πρώην Λίμνη Γιαννιτσών, στην παρούσα μελέτη, θεωρήθηκαν σαν ένα ενιαίο αρδευτικό δίκτυο. Επιπρόσθετα μελετήθηκαν δύο περιπτώσεις, όπου κάθε περίπτωση αποτελείται από 6 κριτήρια. Η πρώτη περίπτωση αποτελείται από τα κριτήρια, του όγκου του αρδευτικού νερού που παροχετεύεται από τον Γ.Ο.Ε.Β. στην καλλιεργητική περίοδο ανά στρέμμα, τη μέση παραγωγικότητα ανά στρέμμα με βάση τις καλλιέργειες, το παραγωγικό κόστος των καλλιεργειών ανά στρέμμα, τις δαπάνες των εκτελεσθέντων έργων συντήρησης και αποκατάστασης των αρδευτικών δικτύων ανά στρέμμα, τη μηχανική σύσταση του κάθε αρδευτικού δικτύου και τη δυνατότητα διάθεσης των παραγόμενων προϊόντων. Η δεύτερη περίπτωση αποτελείται από τα κριτήρια, των αναγκών των καλλιεργειών σε αρδευτικό νερό στην καλλιεργητική περίοδο ανά στρέμμα, τη μέση παραγωγικότητα ανά στρέμμα με βάση τις καλλιέργειες, το παραγωγικό κόστος των καλλιεργειών ανά στρέμμα, τον προϋπολογισμός έργων συντήρησης και αποκατάστασης των αρδευτικών δικτύων ανά στρέμμα, τη μηχανική σύσταση του κάθε αρδευτικού δικτύου και τη δυνατότητα διάθεσης των παραγόμενων προϊόντων.

scholarly journals Strength of nonhuman primate studies of developmental programming: review of sample sizes, challenges, and steps for future work

2019 ◽  
Vol 11 (3) ◽  
pp. 297-306 ◽  
Author(s):  
Hillary F. Huber ◽  
Susan L. Jenkins ◽  
Cun Li ◽  
Peter W. Nathanielsz
Keyword(s):  
Group Size ◽  
Nonhuman Primate ◽  
Statistical Power ◽  
Maternal Obesity ◽  
Developmental Programming ◽  
Sample Sizes ◽  
Minimum Group ◽  
Mode 3 ◽  
Future Work ◽  
Maximum Group

AbstractNonhuman primate (NHP) studies are crucial to biomedical research. NHPs are the species most similar to humans in lifespan, body size, and hormonal profiles. Planning research requires statistical power evaluation, which is difficult to perform when lacking directly relevant preliminary data. This is especially true for NHP developmental programming studies, which are scarce. We review the sample sizes reported, challenges, areas needing further work, and goals of NHP maternal nutritional programming studies. The literature search included 27 keywords, for example, maternal obesity, intrauterine growth restriction, maternal high-fat diet, and maternal nutrient reduction. Only fetal and postnatal offspring studies involving tissue collection or imaging were included. Twenty-eight studies investigated maternal over-nutrition and 33 under-nutrition; 23 involved macaques and 38 baboons. Analysis by sex was performed in 19; minimum group size ranged from 1 to 8 (mean 4.7 ± 0.52, median 4, mode 3) and maximum group size from 3 to 16 (8.3 ± 0.93, 8, 8). Sexes were pooled in 42 studies; minimum group size ranged from 2 to 16 (mean 5.3 ± 0.35, median 6, mode 6) and maximum group size from 4 to 26 (10.2 ± 0.92, 8, 8). A typical study with sex-based analyses had group size minimum 4 and maximum 8 per sex. Among studies with sexes pooled, minimum group size averaged 6 and maximum 8. All studies reported some significant differences between groups. Therefore, studies with group sizes 3–8 can detect significance between groups. To address deficiencies in the literature, goals include increasing age range, more frequently considering sex as a biological variable, expanding topics, replicating studies, exploring intergenerational effects, and examining interventions.

Inverse semigroups generated by a pair of subgroups

1977 ◽  
Vol 77 (1-2) ◽  
pp. 9-22 ◽  
Author(s):  
D. B. McAlister
Keyword(s):  
Inverse Semigroup ◽  
Free Product ◽  
Homomorphic Image ◽  
Main Part ◽  
Structure Theorem ◽  
Inverse Semigroups ◽  
Infinite Cyclic Group ◽  
The Third ◽  
Group A ◽  
Maximum Group

SynopsisThe aim of this paper is to describe the free product of a pair G, H of groups in the category of inverse semigroups. Since any inverse semigroup generated by G and H is a homomorphic image of this semigroup, this paper can be regarded as asking how large a subcategory, of the category of inverse semigroups, is the category of groups? In this light, we show that every countable inverse semigroup is a homomorphic image of an inverse subsemigroup of the free product of two copies of the infinite cyclic group. A similar result can be obtained for arbitrary cardinalities. Hence, the category of inverse semigroups is generated, using algebraic constructions by the subcategory of groups.The main part of the paper is concerned with obtaining the structure of the free product G inv H, of two groups G, H in the category of inverse semigroups. It is shown in section 1 that G inv H is E-unitary; thus G inv H can be described in terms of its maximum group homomorphic image G gp H, the free product of G and H in the category of groups, and its semilattice of idempotents. The second section considers some properties of the semilattice of idempotents while the third applies these to obtain a representation of G inv H which is faithful except when one group is a non-trivial finite group and the other is trivial. This representation is used in section 4 to give a structure theorem for G inv H. In this section, too, the result described in the first paragraph is proved. The last section, section 5, consists of examples.

Impact of instructional decisions on the effectiveness of cooperative learning in chemistry through meta-analysis

2017 ◽  
Vol 18 (1) ◽  
pp. 271-278 ◽  
Author(s):  
Andrew Apugliese ◽  
Scott E. Lewis
Keyword(s):  
Cooperative Learning ◽  
Group Size ◽  
Meta Analysis ◽  
Educational Reforms ◽  
Instructional Decisions ◽  
Wide Range ◽  
Pedagogical Interventions ◽  
Class Period ◽  
The Impact ◽  
Maximum Group

Meta-analysis can provide a robust description of the impact of educational reforms and also offer an opportunity to explore the conditions where such reforms are more or less effective. This article describes a meta-analysis on the impact of cooperative learning on students’ chemistry understanding. Modifiers in the meta-analysis are purposefully chosen to model instructors’ decisions in implementing cooperative learning. Modifiers investigated include: using cooperative learning periodically or in every class period; setting a maximum group size at four or smallerversusfive or larger; using closed-ended or open-ended assessments; and assessing a single topic or assessing the cumulative topics in the course. The results showed cooperative learning's effectiveness is robust across a wide range of instructional decisions except no evidence of effectiveness was found with cumulative assessments. The overall results from the meta-analysis provide a benchmark for evaluating future efforts to evaluate pedagogical interventions in chemistry.

Propagation of long waves due to atmospheric disturbances on a rotating sea

1956 ◽  
Vol 233 (1195) ◽  
pp. 556-569 ◽  
Keyword(s):  
Steady State ◽  
Long Waves ◽  
Pressure Gradients ◽  
Constant Amplitude ◽  
Rotating System ◽  
Dispersive Waves ◽  
Atmospheric Disturbances ◽  
The Waves ◽  
Steady State Amplitude ◽  
Maximum Group

Long waves in shallow water in a non-rotating system are not dispersive but in a rotating system they are. This paper investigates the generation and propagation of these dispersive waves in an infinite sea. The mode of generation is by air-pressure gradients or wind stresses applied to the surface. Bottom friction is neglected. The surface elevation due to a stationary force of constant amplitude suddenly applied and maintained at t = 0 over one-half of an infinite sea is shown to approach, through a series of oscillations approximating more or less to an inertia period, a steady-state amplitude decreasing with distance from the generating area, The longitudinal and transverse velocities are also given. The time elapsed from the initial disturbance at a point to the first maximum of elevation decreases with the distance of the point from the edge of the generating area. A generating area whose edge moves forward with the maximum group velocity of the waves is shown to lead to an elevation of ever-increasing height. The effect of a barrier placed at right angles to the direction of propagation is also briefly considered.

scholarly journals The effect of linkages in the Hierarchical Clustering of Auto-Regressive algorithm for Defect Identification in Heat Exchanger Tubes

2019 ◽  
Vol 8 (4) ◽  
pp. 5003-5009
Keyword(s):  
Pattern Recognition ◽  
Heat Exchanger ◽  
Hierarchical Clustering ◽  
Stress Wave ◽  
Stress Waves ◽  
Clustering Method ◽  
Defect Identification ◽  
Auto Regressive ◽  
Pattern Recognition Approach ◽  
Maximum Group

Pattern recognition approach based on Auto-Regressive (AR) algorithm is an alternative way to provide a more accurate defect identification from stress wave propagated along ASTM A179 heat exchanger tubes. The AR algorithm characterizes the shape of the stress wave signals by AR coefficients and clustered using ‘centroid’ linkages. However, the increase of number of stress waves limiting the function of clustering into meaningful groups. This paper proposes the ‘ward’ linkages as an improved hierarchical clustering method to define the defect features from the reference tube signals and those from the artificially induced defective tubes. The clustering results from the ‘ward’ linkages were represented via a dendrogram showing the hidden pattern between clusters. The defect in the heat exchanger tubes are easily interpreted from the dendrogram and can be successfully identified from Maximum Group Distance Criteria (MGDC). The pattern recognition approach using ‘ward’ linkages in AR algorithm has been shown to effectively identify the defects in the heat exchanger tubes

Tunable Terahertz Plasmon-Induced Transparency in Resonator-Coupled Dirac Semimetal Waveguides

2021 ◽  
Vol 36 (6) ◽  
pp. 676-683
Author(s):  
Daobin Wang ◽  
Jiahuan Yang ◽  
Wei Wang ◽  
Lihua Yuan ◽  
Xiaoxiao Li
Keyword(s):  
Optical Properties ◽  
Fermi Energy ◽  
Delay Time ◽  
Group Delay ◽  
The Finite Element Method ◽  
Group Delay Time ◽  
Dirac Semimetal ◽  
Induced Transparency ◽  
Maximum Group ◽  
Plasmon Induced Transparency

The bulk Dirac semimetal (BDS) is an interesting material, similar to graphene, which can dynamically adjust its optical properties via a variation in its Fermi energy or electrical voltage. In this work, a BDS-based plasmonic device, which enables tunable terahertz plasmon-induced transparency, was proposed and designed. By using the finite element method, the surface plasmon polariton and plasmon-induced transparency of this device were systematically investigated. The results demonstrate that the plasmon-induced transparency of such device can be dynamically tuned by varying its Fermi energy. When the Fermi energy changes from 55 meV to 95 meV, the maximum group delay time of the device increases from 13.2 ps to 21 ps. In the case of a cascading device, the maximum group delay time can be further pushed up to 44.57 ps. The influence of the ambient refractive index on the optical properties of the proposed device was also considered and investigated.

scholarly journals On 𝓠-regular semigroups

2018 ◽  
Vol 16 (1) ◽  
pp. 522-530
Author(s):  
Xinyang Feng
Keyword(s):  
Direct Product ◽  
Homomorphic Image ◽  
Regular Semigroups ◽  
Subdirect Products ◽  
Maximum Group

AbstractIn this paper, we give some characterizations of 𝓠-regular semigroups and show that the class of 𝓠-regular semigroups is closed under the direct product and homomorphic images. Furthermore, we characterize the 𝓠-subdirect products of this class of semigroups and study the E-unitary 𝓠-regular covers for 𝓠-regular semigroups, in particular for those whose maximum group homomorphic image is a given group. As an application of these results, we claim that the similar results on V-regular semigroups also hold.

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