Wyniki wyszukiwania - BazTech

1

Methods for designing and fabrication large-size medical models for orthopaedics

Kudasik T., Libura M., Markowska O., Miechowicz S.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2015

|

Vol. 63, nr 3

623--627

EN

Computed tomography and rapid prototyping techniques can be used to construct and fabricate large size bone models for orthopaedics. Rapid Prototyping technology enables the fabrication of a true-to-scale bone joint model based on 3D virtual models, generated by segmenting patients’ CT images. The model can be used to plan, to simulate, to assist prosthesis implantation for difficult cases of THR (Total Hip Replacements). The main restriction of implementing such models into medical practice is high cost of their production. Physical models of pelvic bones, were constructed on the basis of data collected during standard CT examinations. A method of development of a large-size model while fulfilling the requirement for reducing the price of model fabrication in the article was presented. The method can be used for fabrication the models with 3DP technique. This paper also discusses the issue of production costs when utilizing other RP techniques as well as their usefulness in practice.

2

On the robustness of optimal solutions for combinatorial optimization problems

Libura M.

Control and Cybernetics

|

2009

|

Vol. 38, no 3

671-685

EN

We consider the so-called generic combinatorial optimization problem, where the set of feasible solutions is some family of subsets of a finite ground set with specified positive initial weights of elements, and the objective function represents the total weight of elements of a feasible solution. We assume that the weights of all elements may be perturbed simultaneously and independently up to a given percentage of their initial values. A feasible solution which minimizes the worst-case relative regret, is called a robust solution. The maximum percentage level of perturbations, for which an initially optimal solution remains robust, is called the robustness radius of this solution. In this paper we study the robustness aspect of initially optimal solutions and provide lower bounds for their robustness radii.

3

Stability and accuracy functions in multicriteria combinatorial optimization problem with [Sigma]-MINMAX and [Sigma]-MINMIN partial criteria

Libura M., Nikulin Y.

Control and Cybernetics

|

2004

|

Vol. 33, no 3

511-524

EN

We consider a vector generic combinatorial optimization problem in which initial coefficients of objective functions are subject to perturbations. For Pareto and lexicographic principles of efficiency we introduce appropriate measures of quality of a given feasible solution from the point of view of its stability. These measures correspond to so-called stability and accuracy functions denned earlier for scalar optimization problems. Then we study properties of such functions and calculate the maximal norms of perturbations for which an efficient solution preserves the efficiency.

4

Problemy związane z przystosowaniem żelbetowej konstrukcji budynku przemysłowego do nowych warunków eksploatacji

Bobulska-Pacek I., Libura M., Derkowski W.

Przegląd Budowlany

|

2003

|

R. 74, nr 9

46-49

5

Znaczenie zjawisk termiczno-skurczowych przy projektowaniu monolitycznych konstrukcji żelbetowych

Bobulska-Pacek I., Libura M., Ziobroń W.

Zeszyty Naukowe. Budownictwo i Inżynieria Środowiska / Akademia Techniczno-Rolnicza w Bydgoszczy

|

2001

|

Z. 32(235)

19-28

PL

W referacie przedstawiono problemy dotyczące konstrukcji z betonu, wynikające z oddziaływań spowodowanych zjawiskami termiczno-skurczowymi. Jak wykazuje praktyka, zjawiska te, dość dobrze rozeznane w zakresie badawczym, nie są należycie doceniane w fazi projektowania i realizacji konstrukcji z betonu. W konsekwencji, projektowane konstrukcje nie sa należycie zabezpieczane przed uszkodzeniami spowodowanymi odkształceniami termiczno-skurczowymi. Zarysowania te, przy wzrastającym zanieczyszczeniu i agresywności środowiska, nie mogą być bagatelizowane z uwagi na zagrożenia korozyjne stali zbrojeniowej. W artykule, na przykładzie jednej z realizacji, przedstawiono uszkodzenia żelbetowych ścian piwnic, powstałe w fazie wznoszenia obiektu, spowodowane zjawiskami termiczno-skurczowymi. Poddano analizie siły wewnętrzne wywołane tymi zjawiskami i oszacowano konieczne zbrojenie, jakie winno być zastosowane w ścianie.

EN

The paper presents problems occuring in concrete structures, resulting from reactions caused by thermal and shrinkage phenomena. As it is indicated by practice, these phenomena are not appropriately appreciated at design stage and in execution of concrete structures. Hence, designed structures are not appropriately protected against damages caused by thermal and shrinkage strains. Based on an example of an erected structure, the paper presents defects of reinforced concrete basement walls, which occurred while erecting the building resulting from thermal and shrinkage phenomena. The authors analysed the values of internal forces induced by these phenomena and estimated necessary reinforcement that should by used in walls. Furthermore, they discussed code recommendations referring to design rules for these types of structures.

6

Quality of solutions for perturbed combinatorial optimization problems

Libura M.

Control and Cybernetics

|

2000

|

Vol. 29, no 1

199-219

EN

We consider a general combinatorial optimization problem in which the set of feasible solutions is defined as a given and fixed family of subsets for some finite ground set. To any element of the ground set the so-called weight is associated. The problem consists in finding a feasible subset for which the sum of weights of its elements is the minimum. When the weights of elements vary or are estimated with some accuracy, then the solution of the problem obtained for some initial weights may appear non-optimal. In this paper we consider the quality of a given solution in the case of weights perturbation or inaccuracy. Namely, we study the relative error of a given solution as a function of particular weights perturbation. We also calculate the maximum perturbation or estimation errors of weights which preserve the optimality of a given solution of the problem.

7

On the accuracy function and the accuracy radius for combinatorial optymization problems

Libura M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2000

|

Vol. 48, nr 2

231-245

EN

We consider the combinatorial optimization problem in the following form: min{EEF c(e) : F E F} -( formula), where for some finite set E, c = (c(e), e E E) E R+ (formula) is a vector of weights of elements of E, and F C 2E (formula) is a given family of feasible subsets. We assume that the set F is fixed, but the weights of elements belonging to some given subset X C E may vary. The accuracy function describes the quality of a given solution of the problem as a function of weights perturbations. Namely, for a given optimal solution Fo obtained for an initial vector of weights ca E R+, the value a( Fo, X, b) of this function for some specified subset X C E and a value b, where 0 < 1, is equal to the maximum relative error of the solution Fo for arbitrary simultaneous perturbations of weights of elements, satisfying the following conditions: Ic(e) - co(e)I

8

Przyczyny uszkodzeń oraz naprawa i wzmocnienie żelbetowych bunkrów w składzie głównym cementowni

Bobulska-Pacek I., Libura M., Matysek P.

Inżynieria i Budownictwo

|

1998

|

R. 54, nr 8

405-407

PL

Przedstawiono wyniki badań konstrukcji żelbetowych bunkrów eksploatowanych od ponad 30 lat. Opracowano projekt rekonstrukcji i wzmocnienia obiektów oraz podano uwagi ogólne dotyczące projektowania, diagnostyki oraz naprawy tego rodzaju budowli.

EN

Results of investigation of damages arised in reinforced concrete group of bunkers which have been used in the main depot of cement plant for more than 30 years have been presented. Reconstruction and strengthening design has been worked out for the structure considered and general remarks dealing with designing diagnostics and repair of these type of structures have been given.