Povećanje kvalitete rezultata površinske hrapavosti kod obrade slobodnih površina temeljem neuronskih mreža

This paper concerns with free form surface reorganization and assessment of free form model complexity, grouping particular surface geometrical properties within patch boundaries, using self organized Kohonen neural network (SOKN). Neural network proved itself as an adequate tool for considering all topological non-linearities appearing in free form surfaces. Coordinate values of point cloud distributed at a particular surface were used as a surface property’s descriptor, which was led into SOKN where representative neurons for curvature, slope and spatial surface properties were established. On a basis of this approach, surface patch boundaries were reorganized in such a manner that finish machining strategies gave best possible surface roughness results. The patch boundaries were constructed regarding to the Gaussian and mean curvature, in order to achieve smooth transition between patches, and in this way preserve or even improve desired curve and surface continuities, (C2 and G2). It is shown that by reorganization of boundaries considering curvature, slope and spatial point distribution, the surface quality of machined free form surface is improved. Approach was experimentally verified on 22 free form surface models which were reorganized by SOKN and machined with finish milling tool-path strategies. Results showed rather good improvement of mean surface roughness profile Ra for reorganized surfaces, when comparing to unorganized free form surfaces.Ovaj se članak bavi reorganizacijom slobodnih površina i ocjenom kompleksnosti modela slobodnih površina, grupirajući određena površinska geometrijska svojstva unutar zatvorenih površina, koristeći samoorganizirajuću Kohonenovu neuronsku mrežu (SOKN). Neuronske mreže pokazale su se kao prikladan alat za razmatranje svih topoloških nelinearnosti koje se pojavljuju kod slobodnih površina. Vrijednosti koordinata oblaka točaka raspodijeljenih nad određenom površinom korišteni su kao svojstveni opis, što je nadalje vodilo prema SOKN-u, gdje su ustanovljeni reprezentativni neuroni za zakrivljenost, nagib i prostorno-površinska svojstva. Na temelju ovoga pristupa reorganizirane su granice zatvorenih površina na takav način da metode površinske obrade daju najbolje moguće rezultate spram površinske hrapavosti. Granice tih površina određene su prema Gaussovoj i prosječnoj zakrivljenosti kako bi se postigao glatki prijelaz između zatvorenih površina te kako bi se na taj način očuvala ili čak unaprijedila željena zakrivljenost i glatkoća površine, (C2 i G2). Pokazano je da se reorganizacijom granica s obzirom na zakrivljenost, nagib i prostornu raspodjelu točaka, poboljšava kvaliteta obrađene slobodne površine. Pristup je eksperimentalno potvrđen na 22 modela slobodne površine koji su reorganizirani SOKN-om i površinski obrađeni određenim metodama. Rezultati pokazuju poprilično dobro poboljšanje prosječne vrijednosti površinske hrapavosti Ra za reorganizirane strukture u usporedbi sa neorganiziranim slobodnim površinama

RAZVOJ I STANJE INTERNE REVIZIJE – REZULTATI DVAJU EMPIRIJSKIH ISTRAŽIVANJA U SLOVENSKIM ORGANIZACIJAMA

Results of (the first) two empirical studies with the aim to reveal the state-of-the-art and development of internal audit in Slovenia are presented in the article. Internal auditing, one of the cornerstones in modern corporate governance, has a relatively short tradition in this new EU member country. Nevertheless, beside the first and mandatory established internal audit units, which were initiated by the corresponding industry’s laws in financial services in the early 90s, there is already evidence of a significant and growing number of non-mandatory, voluntary established internal auditing units in other industries. And a variety of internal audit practices regarding establishment, reporting lines, size and scope of work performed by internal audit units, and professional qualifications of internal auditors characterizes the current profile of internal auditing in Slovenian organisations. It can be concluded that internal auditing in Slovenia is following the trends of practice in developed countries, although, in some cases internal auditors are facing problems, mainly due to their lack of work experience, to (un)professionality of corporate governing bodies, and to top management’s lack of awareness or even misunderstanding of the role of internal auditing in corporate governance.U ovom članku se prvi put prezentiraju rezultati provedena dva empirijska istraživanja, čiji je bio cilj istražiti i javnosti prezentirati dostignuti stupanj razvoja interne revizije u Sloveniji. Danas se interna revizija percipira kao jedan od temeljnih nositelja modernog korporacijskog upravljanja, iako se relativno kratko primjenjuje u zemljama, koje su nove članice EU. Početak ustrojavanja interne revizije u ovim zamljama se vezuje uz rane 90-te godine, kada su propisi obvezivali institucije financijskog sektora na uvođenje interne revizije, ali su daleko značajniji podaci da je inerna revizija prisutna i u velokom broju poslovnih sustava iz drugih djelatnosti u kojima je ustrojena na dobrovoljnoj osnovi. Način ustrojavanja interne revizije u praksi nije jedinstven, već se prepoznaju različiti organizacijski oblici i polazišta utemeljenja kao i način izvješćivanja, te veličina službe i razina obuhvata rezultata. Pored toga, istraživanje provedeno u poslovnim sustavima ukazuju da nema jedistvenog pristupa u zahtjevima za obrazovnim nivoom i razinom profesionalne osposobljenosti internih revizora u Sloveniji. Može se zaključiti da razvoj interne revizije u Sloveniji prati trendove prisutne u praksi razvijenih zemalja, premda se pojedini interni revizori suočavaju i s velikim brojem praktičnih problema. Naime, ti su problemi u pravilu povezani s (ne)profesionalnim odnosom tijela ili menadžmenta u sustavu korporativnog upravljanja prema internoj reviziji, najčešće zbog nepoznavanja suštine problema ili zbog krivog shvaćanja mjesta i uloge interne revizije u sustavu korporativnog upravljanja

Intelligent tool path generation for milling of free surfaces using neural networks

The presented paper has an intention to show how with the help of Artificial Neural Network (ANN), the prediction of milling tool-path strategy could be made in order to establish which milling path strategy or their sequence will show the best results (will be the most appropriate) at free surface machining, according to set technological aim. In our case the best possible surface quality of machined surface was taken as the primary technological aim. Configuration of used Neural Network (NN) is presented, and the whole procedure is shown on an example of mould, for producing light switches. The verification of machined surface quality, according to average mean roughness, Ra, is also being done, and compared with the NN predicted result

Neural network based manufacturability evaluation of free form machining

Most CAD/CAM and computer-aided process planning systems manipulate all geometrical features on the part equally. In the area of free form machining, lack of efficient methodology for assessing the degree of manufacturing pretentiousness of free form features is still noticeable. Developing this methodology inside CAD/CAM systems brings the following benefits to the tool shop praxis: it minimizes the number of set-ups and tool changes and at the same time ensures the right sequence of machining strategies in order to achieve the best possible surface quality in the machining area. Based on this assessment, the CAD/CAM process will also be greatly simplified. When there are an increased number of non-prismatic and non-cylindrical features, this problem is even more exaggerated, and its solution cannot be found in the framework of analytical mathematics. This paper reports a neuro-fuzzy model that uses the concept of "feature manufacturability" to identify and recognize the degree of "pretentiousness-difficulty of machining". The model is created by means of the construction of parametric fuzzy membership functions, based on neural networks learning process. This makes possible simultaneous evaluation of features complexity in a CAD model and manufacturing capability in an environment description model

The influence of parental education and other socio-economic factors on child car seat use

The behaviour of parents in ensuring car passenger safety for their children is associated with socio-economic (SE) status of the family; however, the influence of parental education has rarely been researched and the findings are contradictory. The aim of the study was to clarify whether parental education influences the use of a child car seat during short rides