Rozprawy doktorskie na temat „Determining sets”

The problem of achieving the sustainable development conditions requires appropriate coordinated actions of many subjects’ of the economicproductive activity. Herewith, an important component of this complex action is to provide the acceptable level of the State’s economic security (ECS) and its individual areas because achieving the sustainable development conditions requires, above all, rational organization of economic activity.

An examination of 14 indexes for determining the number of clusters is conducted on artificial binary data sets being generated according to various design factors. To provide a variety of clustering solutions the data sets are analyzed by different non hierarchical clustering methods. The purpose of the paper is to present the performance and the ability of an index to detect the proper number of clusters in a binary data set under various conditions and different difficulty levels. (author's abstract)
Series: Working Papers SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

Over recent years, the interest in the study of subjective well-being (SWB) has increased more and more. One of the main discussions among academics and policy makers is whether SWB may be correlated with the level of both relative and absolute level of income. Subjective well-being measures are gaining popularity as a proxy of utility, even though its relationship with income is still unclear. In his seminal work, (Easterlin1974) basically pointed out that there is no relation between average income of a country and its level of happiness. Nevertheless, other influential works by (Sacks2013, Stevenson2008) argued that the correlation exists, it follows a linear-log relationship and moreover there is no evidence of a satiation point. The primary goal of this dissertation is to study more in depth the relationship between income and subjective well-being, in particular with life satisfaction and happiness, trying to challenge both `schools of thought'. Furthermore, in contrast with theories of `happy degrowth', I try to show the importance of economic growth and prosperity in determining happiness, and more in general human well-being.

E-commerce has been the subject of a massive growth in the course of the last decade, with the fashion industry being one the the main beneficiary of this growth, being the largest B2C eCommerce market segment with a market size estimated at US$752.5 billion in 2020 and a growth compound rate of 9.1% per year. In such a context, fashion e-commerce is easily identifiable as one of the most profitable sectors globally, but at the same time one of the most competitive as well. This thesis starts with a review of the history and the roots of the modern e-commerce website, goes on outlining a theoretical framework touching e-commerce definitions, e-commerce types, e-commerce main benefits compared to other sale channels. It then proceeds exposing a detailed practical framework of how an e-commerce is composed, what are the current main e-commerce platforms and their peculiarities, and what are the main fashion e-commerce trend strategies and best practices. Finally, the aim of the thesis is to study empirically, through the somministration of online questionnaires, which are the leading key success factors for a profitable e-commerce in the fashion industry, with a particular focus on whether the most successful factors in generating purchase intention are related to the quality and the ease of use of the website or the marketing and communication activities that the brands carry out around their e-commerce websites. Involvement with the product category is used as the moderator element influencing the studied correlations.

Sustainability has become a global and important issue, as a consequence of the environmental degradation that can be tracked back to the industrial revolution. States, firms and individuals must take actions in order to avoid environmental catastrophes, by creating and respecting new laws, changing the production system and adopting different consumption behaviors. In ensuring sustainable consumption and production patterns, the fashion industry is one of the most important players, since it is sadly known to be characterised by high water usage, pollution, labour issues in developing countries and the difficulty of recycling fashion products which eventually finish in landfills or are incinerated. The concept of sustainable fashion was introduced for the first time during the sixties when fashion consumers started to reflect on the repercussions of their consumption behaviour on the environment. This study adds to the topic of sustainable fashion, in particular to the sustainable apparel consumption behavior. The aim is to prove the relationship between the individual’s personality traits and the purchase likelihood and willingness to pay for sustainable apparel. The personality traits examined are impulsivity, localism, need for uniqueness and frugality, with the additional purpose to test the moderation effect of anxiety on the relationship between impulsivity and purchase likelihood/ WTP and the influence of cynicism in moderating the relation of frugality with purchase likelihood and WTP for sustainable apparel. The hypotheses have been tested through a quantitative research model; the answers have been collected by means of a questionnaire involving a sample of 100 people. The hypothesized relationships have been tested through partial least squares structural equation modeling technique. The results reveal that cynicism and need for uniqueness have a significant impact on purchase likelihood and willingness to pay. The findings of this study are a contribution to the analysis of purchasing behavior and willingness to pay for sustainable apparel; they may help marketers in planning targeted strategies and methods to increase sales. Despite of the increasing interest in sustainable fashion characterizing the last few years, this argument is still new and little known to a large part of the population, as this research demonstrates. This study, compared to others who deal with the purchasing likelihood or willingness to pay for sustainable fashion, analyze empirically some specific personality traits. Impulsivity, localism, need for uniqueness, frugality, anxiety and cynicism have been specifically taken into consideration because it has been scientifically proven that they describe a consumer concerned about the environment and/or a fashion addict buyer. By testing and evaluating the hypotheses it is possible to identify which are (or are not), the characteristics of a typical sustainable fashion consumer and increase the awareness on this important topic.

The analysis of three companies that have jointly considered the technical and the social systems while designing and implementing the new digital technologies shows how and to what extent the Socio-Technical Systems (STS) principles are nowadays adopted, thereby indicating the possibility that the STS theory can (re) become central in both theory and managerial practices. Thereby we propose an ‘actualized’ sociotechnical design approach, capable in aligning an organization to the rapid and radical change that come along with the digitalization and indicate that the application of STS-informed design methods, such as Agile and Design Thinking, oriented more to action and intervention, mirroring the actual act of designing in a dynamic way, but also offer organizations the opportunity to embrace a broader stakeholder base.

Questo lavoro esamina alcuni dei possibili fattori alla base del rapido aumento dei prezzi dei cereali (grano, mais e soia) sul mercato internazionale dal 2002 e stima il contributo di un set di variabili macroeconomiche e finanziarie che condizionano le curve di domanda e offerta. L'analisi econometrica ha quindi cercato di evidenziare l'esistenza di una relazione di equilibrio utilizzando un modello a correzione dell'errore per poi occuparsi del fenomeno di variabilità in termini di volatilità storica utilizzando un modello nelle sole differenze.

Questo lavoro esamina alcuni dei possibili fattori alla base del rapido aumento dei prezzi dei cereali (grano, mais e soia) sul mercato internazionale dal 2002 e stima il contributo di un set di variabili macroeconomiche e finanziarie che condizionano le curve di domanda e offerta. L'analisi econometrica ha quindi cercato di evidenziare l'esistenza di una relazione di equilibrio utilizzando un modello a correzione dell'errore per poi occuparsi del fenomeno di variabilità in termini di volatilità storica utilizzando un modello nelle sole differenze.

In questa tesi modelliamo l'evoluzione nel ciclo di vita delle spese sanitarie individuali (HCE), espresse in funzione del processo di invecchiamento, degli shock e delle condizioni di salute e della distanza dalla morte. Tutte le analisi sono condotte utilizzando un unico dataset, che permette di analizzare diversi tipi di servizi sanitari e diversi sottocampioni di individui. La popolazione di interesse è costituita da individui di età compresa tra i 50 e i 70 anni, la finestra di età in cui si verificano i primi eventi sanitari avversi. Nel primo capitolo, usiamo un two-way fixed effects model per esaminare l'effetto dell'età, della morbilità e della distanza al decesso (TTD) sulle spese sanitarie individuali. La stima viene effettuata includendo diversi controlli, compresi gli effetti fissi individuali e del medico di medicina generale. Indaghiamo anche in che misura le caratteristiche dei pazienti e dei medici di base contribuiscono alla variabilità complessiva delle spese tra gli individui. I nostri risultati principali mostrano che l'età, la morbilità e TTD sono tutti importanti determinanti della spesa e sono tra gli elementi che contribuiscono maggiormente alla variabilità della stessa tra gli individui. La spesa totale aumenta con l'età, e quest'ultima risulta essere correlata negativamente con il tempo alla morte, un risultato in contrasto con la “red herring” hypothesis. Tale aumento con l'età delle spese complessive è principalmente guidato dalle spese per i servizi extra-ospedalieri; al contrario, non si osserva alcuna differenza nei costi ospedalieri durante la durata l’arco di vita considerato, una volta presi in considerazione gli altri fattori. D'altra parte, le spese ospedaliere guidano principalmente i profili di morbilità e di fine vita della spesa totale. Per quanto riguarda l'analisi di eterogeneità, gli individui cronici e disabili con shock sanitari che richiedono l'ospedalizzazione sono quelli che gravano maggiormente sui costi sostenuti dal sistema sanitario italiano. Ciò suggerisce che il potenziamento degli approcci preventivi prima dell'insorgenza di tali shock è un obiettivo di policy prioritario per ridurre l'incidenza delle malattie di lunga durata ed evitare che queste si aggravino fino a trasformarsi in casi acuti che richiedono ricoveri ospedalieri. Dati i risultati ottenuti nel primo capitolo, nel secondo usiamo un difference-in-difference event study per stimare l'impatto a breve e lungo termine dell'ospedalizzazione sulla spesa sanitaria individuale. In questo capitolo, i ricoveri ospedalieri sono analizzati come sottoinsieme misurabile di quei primi eventi sanitari avversi che gli individui di 50-70 anni sperimentano nella loro vita. I nostri risultati principali confermano l'esistenza di un effetto rilevante del primo ricovero sulla spesa e mostrano che il primo accesso è associato a sostanziali spese mediche future in tutti i contesti sanitari, e soprattutto nel settore delle cure ospedaliere acute. L'analisi delle spese ospedaliere infatti indica il verificarsi di successivi ricoveri, richiesti principalmente per complicazioni di malattie cardiovascolari e cancro. Queste patologie sono responsabili del maggiore aumento delle spese di ricovero e presentano un persistente aumento post-ricovero anche nelle spese ambulatoriali e farmaceutiche, un risultato guidato dall'alta incidenza di individui cronici e disabili all'interno del gruppo degli individui affetti da queste due condizioni. Da un punto di vista di policy, questo risultato indica la necessità di un rafforzamento dell'assistenza territoriale e di miglioramenti nella prevenzione terziaria, necessari per attenuare l'impatto delle malattie croniche e di lunga durata in corso. Da un lato, questo migliorerebbe la salute dei pazienti prevenendo complicazioni e casi acuti; dall'altro, genererebbe un risparmio significativo attraverso la riduzione di ricoveri evitabili.
In this thesis, we model the life-cycle evolution of individual healthcare expenditures, expressed as a function of the aging process, health shocks and conditions, and distance to death. All the analyses are carried out by using a unique dataset, which allows us to focus on different types of healthcare services and different subsamples of individuals. The population of interest consists of individuals aged 50-70, the age window where the first adverse health events are expected to arise. In the first chapter, we use a two-way fixed effects model to examine the effect of age, morbidity, and time to death (TTD) on individual healthcare expenditures (HCE). The estimation is carried out by controlling for several confounding factors, including individual and General Practitioner (GP) fixed effects. We also investigate to what extent patients’ and GP’ characteristics contribute to the overall variability in expenditures among individuals. Our main results show that age, morbidity, and TTD are all important determinants of HCE and are among the elements that contribute most to the variability in HCE among individuals. Total HCE is increasing in age, with the latter found to be negatively correlated with the time to death, a result in contrast with the ‘red herring’ hypothesis. Such an increase with age of overall expenditures is mainly driven by expenses for out-of-hospital services; in contrast, no difference in hospital costs is observed over the considered lifespan once the other factors are taken into account. On the other hand, inpatient expenditures mainly drive the morbidity and end-of-life profiles of total HCE. Concerning heterogeneous analysis, we find that chronic and disabled individuals with health shocks requiring hospitalization are those who place the greatest burden on the costs borne by the Italian healthcare system. It suggests that the enhancement of preventive approaches before the onset of such shocks is a priority goal to reduce the incidence of long-lasting diseases and prevent them from deteriorating to the point of exacerbation in acute cases requiring hospital admissions. Given the results obtained in the first chapter, in the second one, we use a difference-in-difference event study approach to estimate the short- and long-run impact of the hospitalization on HCE, with hospital admissions analyzed here as a measurable subset of those first adverse health events individuals aged 50-70 experience in their life. Our main findings confirm the existence of a large effect of the first hospitalization on HCE and show that the first access is associated with substantial future medical expenses in all healthcare settings, accounted for the largest part by acute inpatient care. Indeed, the analysis of hospital expenditures indicates the occurrence of subsequent hospitalizations, mainly required for complications of cardiovascular diseases and cancer. The latter are responsible for the highest increase in inpatient expenditures and present a persistent post-admission increase also in outpatient and pharmaceutical expenses, a result driven by the high incidence of chronic and disabled individuals within the group of those affected by these two conditions. From a policy perspective, it indicates need for a strengthening of territorial care and tertiary prevention improvements, necessary to soften the impact of ongoing illnesses with lasting effects. On the one hand, it would improve patients’ health by preventing complications and acute cases; on the other hand, it would also generate significant savings through reduced avoidable additional hospitalizations.

碩士
中原大學
資訊工程研究所
104
With the development of fuzzy theory, the number of fuzzy sets in fuzzy control is the factor that influences control decisions, thus the main purpose of this study is to investigate ways to determine the number of fuzzy sets and the division method through the distribution of data. This study provides a method of assessment, which determines the method to estimate the number of fuzzy sets and the fuzzy division through different simplified levels. Since the simplification is based on the degree of disorder to consolidate rules, it is observed through the change in accuracy and the number of rules that as the former declines less, the latter declines more, and this indicates that the number of fuzzy sets and fuzzy division in this method are suitable for the given dataset. In this study, three fuzzy divisions, Fuzzy C-Means (FCM), Hierarchical Fuzzy Partitioning (HFP) and Regular, are compared and four different methods including Partition Entropy (PE), Information Gain (IG), Relief-F (RF) and Wang &; Mendel (WM), which are used to estimate number of fuzzy sets. After referring to information on numerical property and classification from UC Irvine Machine Learning Repository (UCI) for this dataset, using FisPro as the fuzzy partition. Fuzzy Decision Trees (FDT) and Wang and Mendel (WM) are used to generate rules, simplification is used for WM to do loss of performance to the degrees of 1%, 5%, 10%, 20% and 30%, and changes in accuracy and number of rules are compared. In particular, loss of performance is used to eliminate rules to improve the efficiency of fuzzy control, however it’s observed from accuracy tests in different divisions that if a certain class lacks data, the class itself may not be established. Therefore, loss of performance is not recommended for some urgent control systems. Suited methods are identified from the experimental results for the datasets. For instance, PE coupled with regular division works better with Iris dataset while RF with FCM suits the Glass and Seeds datasets, IG with FCM suits Page Blocks and RF with HFP suits the Statlog(Shuttle) dataset. As for FDT, since it can select the crucial fuzzy sets out of a vast amount of fuzzy set individuals for judgement, method of IG with FCM suits FDT better.

This thesis explores the interplay between complex geometry and operator theory, focusing on characterizing certain objects from algebraic geometry. Two concepts that have been of prime importance in recent times in the analysis of Hilbert space operators are distinguished varieties, which are a priori geometric in nature, and joint spectra, which are a priori algebraic in nature. This thesis brings them together to characterize all distinguished varieties with respect to the bidisc, more generally the polydisc and the symmetrized bidisc in terms of the joint spectrum of certain linear pencils. Some of the results are shown to refine earlier work in these directions. The binding force is provided by an operator-theoretic result, the Berger-Coburn-Lebow characterization of a tuple of commuting isometries. The thesis then turns to studying the uniqueness of solutions of the solvable NevanlinnaPick interpolation problems on the symmetrized bidisc and its connection with distinguished varieties. Several sucient conditions have been identified for a given data to have a unique solution. Moreover, for a class of solvable data on the symmetrized bidisc, there exists a distinguished variety where all solutions agree. Additionally, the thesis explores the more general concept of the determining sets.