1,367 research outputs found
Stochastic Nonparametric Envelopment of Data: Combining Virtues of SFA and DEA in a Unified Framework
No full textThe literature of productive efficiency analysis is divided into two main branches: the parametric Stochastic Frontier Analysis (SFA) and nonparametric Data Envelopment Analysis (DEA). This paper attempts to combine the virtues of both approaches in a unified framework. We follow the SFA literature and introduce a stochastic component decomposed into idiosyncratic error and technical inefficiency components imposing the standard SFA assumptions. In contrast to the SFA, we do not make any prior assumptions about the functional form of the deterministic production function. In this respect, we follow the nonparametric route of DEA that only imposes free disposability, convexity, and some specification of returns to scale. From the postulated class of production functions, the proposed method identifies the production function with the best empirical fit to the data. The resulting function will always take a piece-wise linear form analogous to the DEA frontiers. We discuss the practical implementation of the method and illustrate its potential by means empirical examples.Productivity Analysis,
COAGULATION OF INDUSTRIAL WASTEWATER WITH NOVEL POLYMERS
No full textNamen diplomske naloge je izboljšati kakovost odpadne vode iz kovinske industrije z uporabo koagulacije. Raziskovali smo učinkovitost zniževanja vrednosti kemijske potrebe po kisiku (KPK) z enim od treh izbranih koagulantov PACl, FeCl3 in Al2(SO4)3 v kombinaciji z enim od dveh flokulantov Amerfloc 425 in Amerfloc 487. Analizirali smo vrednosti pH, SAK, prevodnost, motnost, KPK in vsebnost anionskih tenzidov. Odvzeli smo tri različne vzorce odpadne vode z različnimi začetnimi vrednostmi KPK. Najboljša kombinacija se je izkazala s PACl v kombinaciji z Amerflocom 487. Vrednost KPK smo znižali pod 150 mg/L O2, kar znaša čez 80 %, s čimer je omogočen izpust čiščene vode v vodotoke.The aim of diploma thesis was to improve the quality of wastewater from metal industry. Three different coagulnts PACl, FeCl3, Al2(SO4)3, and two different polymers Amerfloc 425 and Amerfloc 487 were chosen. The combination of selected chemicals were tested in order to decrease chemical oxygen demand (COD). We analyzed the pH, spectral absorption coefficient at 254 nm, conductivity, COD, turbidity and the anionic surfactants content in waste water. The combination of PACl and Amerfloc 487 was the most successfull in COD removal. We managed to lower COD below 150 mg/L O2, which means above 80 % removal efficiency. The treated wastewater could be released into environement
Chemical recycling of polyethylene terephthalate and characterization of degradation products
No full textV zadnjih letih je zaradi vse višjega življenjskega standarda ter rasti prebivalstva, močno narasla količina proizvedenih in uporabljenih tekstilnih materialov. Povečala se je tudi količina odpadnega tekstila, lahko pa sklepamo, da se bo ta v prihodnje še povečala. Polietilen tereftalat je danes tretji najbolj razširjen polimer, za polietilenom in polipropilenom. V tekstilni industriji je najbolj uporabljen sintetični material za izdelavo vlaken.
V raziskavi smo se ukvarjali s problematiko recikliranja PET vlaken. Predpostavljali smo, da bomo kot glavni produkt izolirali monomer tereftalne kisline.
Metoda, ki smo jo uporabili je nevtralna hidroliza PET vlaken v visokotlačnem reaktorju, ki nam omogoča višjo čistost izhodnih snovi – tereftalne kisline in etilen glikola. Izvedli smo izolacijo in čiščenje nastalih produktov s pomočjo kislinsko bazne ekstrakcije in destilacije. Nastale produkte smo analizirali z infrardečo spektroskopijo.
Cilj magistrskega dela je bil raziskati razgradne produkte po kemijskem recikliranju PET vlaken v visokotlačnem reaktorju pod različnimi pogoji. Spreminjali smo temperaturo, čas in razmerje med uporabljenim tekstilnim materialom in topilom in nato analizirali nastale razgradne produkte.
Ugotovili smo, da so pride do popolne depolimerizacije PET vlaken do tereftalne kisline pri naslednjih pogojih: T = 250 °C in t = 10 min (vzorec D2).Increasing standard of living and population growth in recent years are the reason the volume of manufactured and used textile materials has increased considerably. The amount of waste textile has increased and we can conclude it will also increase in the future. Polyethylene terephthalate is the third most common polymer, after polyethylene and polypropylene. It is the most used synthetic fiber in the textile industry.
In the research we dealt with the problem of recycling PET fibers. We assumed that as the main product we would isolate the monomer of terephthalic acid.
The methods we used are the neutral hydrolysis of PET fibers in the high-pressure reactor, which enables us to achieve higher purity of the starting materials – terephtalic acid and ethylene glycol. We isolated and purified the resulting products by acid base extraction and distillation. The resulting products were analyzed by infrared spectroscopy.
The aim of this master\u27s thesis was to investigate the degradation of the products after chemical recycling of PET fibers in a high-pressure reactor under different conditions. We changed the temperature, time and ratio between the used textile material and the solvent, and then we analyzed the resulting products.
We found out that complete depolymerisation was achieved at following conditions: T = 250 ° C and t = 10 min (sample D2)
The Portrayal of Family and Self-reflexivity in Luigi Pirandello’s Six Characters in Search of an Author
No full textLuigi Pirandello’s play, Six Characters in Search of an Author (1921, Sei personaggi in cerca d’autore)
portrays numerous significant and functional characteristics of metatheatre, a concept coined by Lionel
Abel. By drawing on such metatheatrical features and the play within a play technique, Pirandello’s play
presents six characters that are in search of an author. This study will, therefore, explain the concept
of metatheatre and present a critical analysis of the play, Six Characters as a self-reflexive play. In this
critical engagement with the text through specific references from the play and relevant secondary sources,
important themes in the play such as reality and illusion, life, art, and the representation of the family in the
play will be analysed. This analysis will ultimately demonstrate that Pirandello presents six characters that
are self-conscious of their position as dramatic characters that manage to act out their roles, which actually
reveal the family relationships between the characters
Double bootstrap confidence intervals in the two-stage DEA approach
No full textContextual factors usually assume an important role in determining firms' productive efficiencies. Nevertheless, identifying them in a regression framework might be complicated. The problem arises from the efficiencies being correlated with each other when estimated by Data Envelopment Analysis, rendering standard inference methods invalid. Simar and Wilson (2007) suggest the use of bootstrap algorithms that allow for valid statistical inference in this context. This article extends their work by proposing a double bootstrap algorithm for obtaining confidence intervals with improved coverage probabilities. Moreover, acknowledging the computational burden associated with iterated bootstrap procedures, we provide an algorithm based on deterministic stopping rules, which is less computationally demanding. Monte Carlo evidence shows considerable improvement in the coverage probabilities after iterating the bootstrap procedure. The results also suggest that percentile confidence intervals perform better than their basic counterpart.Peer reviewe
New Models for Data Envelopment Analysis. Measuring Efficiency Outwith the VRS Frontier
No full textSome models are presented in this paper which extend the concept of measuring superefficiency to the useful case of variable returns-to-scales (VRS), thus enabling the ranking of efficient as well as inefficient units. Two models, namely the Universal Radial Model and the Universal Additive Model, are presented that also have strong invariance properties (units and translation invariance). For both of these models a method for normalising the efficiency scores on a (0-1+) scale is presented. These models have been implemented in a software package and applied to the ranking of units in an industrial context.Data envelopment analysis (DEA), Superefficiency, Universal models
Measuring the relative efficiency of banks using DEA method
No full textData Envelopment Analysis (DEA) is one of the most popular methods used for measuring the relative efficiency of similar units by considering various input/output parameters. This paper implements DEA models to estimate the relative efficiency of selected banks in the United States. The proposed study uses two inputs, total assets and number of employees, and one output, net revenue for measuring the relative efficiency of selected banks. The relative efficiencies of different banks are analyzed. The preliminary results indicate that Santander Bank is the most efficient banks operating in the United States followed by SunTrust Bank and HSBC. Other banks preserve lower efficiency compared with these three banks.Peer reviewedFinal article published.Data envelopment analysis (DEA)EfficiencyBank industr
Stochastic DEA
No full textInternational audienceData Envelopment Analysis (DEA) was introduced as a linear programming model by Charnes et al. (Eur J Oper Res 2:429\textendash444, 1978) and Banker et al. (Manag Sci 30:1078\textendash1092, 1984) as a nonparametric model to estimate frontier production and technical efficiency using linear programming. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG
Basic analytical capabilities of the CCR-DEA model
No full textThe article describes some analytical applications of the basic DEA model – CCR model proposed by Charnes, Cooper and Rhodes [2]. The author presents elementary DEA profiles, terminology, ideas and some traditional ways of determining the optimal technology for inefficient objects and benchmarking and estimating the type and size of returns to scale. The evaluation of input excess and output shortage is also described. In this context, the author suggests an economic interpretation of the optimal solution of the CCR model as a task that consists of creating virtual technology of a given set of objects. The author also presents how to determine the structure of a target and optimal technology and indicates the way of using simplex reports in sensitivity analysis of the solution to the CCR model. All these reflections are illustrated by a real-life DEA problem that concerns bank efficiency.CCR-DEA, interpretation of CCR model, Optimal technology structure
Rice growing farmers efficiency measurement using a slack based interval DEA model with undesirable outputs
No full textIn recent years eco-efficiency which considers the effect of production process on environment in determining the efficiency of firms have gained traction and a lot of attention. Rice farming is one of such production processes which typically produces two types of outputs which are economic desirable as well as environmentally undesirable. In efficiency analysis, these undesirable outputs cannot be ignored and need to be included in the model to obtain the actual estimation of firm’s efficiency. There are numerous approaches that have been used in data envelopment analysis (DEA) literature to account for undesirable outputs of which directional distance function (DDF) approach is the most widely used as it allows for simultaneous increase in desirable outputs and reduction of undesirable outputs. Additionally, slack based DDF DEA approaches considers the output shortfalls and input excess in determining efficiency. In situations when data uncertainty is present, the deterministic DEA model is not suitable to be used as the effects of uncertain data will not be considered. In this case, it has been found that interval data approach is suitable to account for data uncertainty as it is much simpler to model and need less information regarding the underlying data distribution and membership function. The proposed model uses an enhanced DEA model which is based on DDF approach and incorporates slack based measure to determine efficiency in the presence of undesirable factors and data uncertainty. Interval data approach was used to estimate the values of inputs, undesirable outputs and desirable outputs. Two separate slack based interval DEA models were constructed for optimistic and pessimistic scenarios. The developed model was used to determine rice farmers efficiency from Kepala Batas, Kedah. The obtained results were later compared to the results obtained using a deterministic DDF DEA model. The study found that 15 out of 30 farmers are efficient in all cases. It is also found that the average efficiency values of all farmers for deterministic case is always lower than the optimistic scenario and higher than pessimistic scenario. The results confirm with the hypothesis since farmers who operates in optimistic scenario are in best production situation compared to pessimistic scenario in which they operate in worst production situation. The results show that the proposed model can be applied when data uncertainty is present in the production environmen
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