364 research outputs found
Pojava pozitivnog i negativnog elastiÄnog povrata pri savijanju lima od mateijala St1403 u V-alatu
Today there is widespread usage of high strength steels (HSS), and ultra
high strength steels (UHSS) in the manufacturing industry. Especially in
the automobile industry for the rigid and light weight chassis components
made out of high strength steel. During sheet metal forming material
undergoes plastic deformations and after the process of forming and taking
out of the tool, formed sheet metal plate try to take previous position and
elastically deforms. This deformation is called elastic spring-back. Special
version of this elastically unloading is called spring-forward. It can be seen
in V-die bending with small punch radius, and small punch angle which is
shown in this paper.Danas postoji Å”iroka upotreba visoko Ävrstih i ultra visoko Ävrstih Äelika
u industriji. Posebno u automobilskoj industriji za izradu krutih i laganih
komponenti karoserija automobila izraÄenih od visoko Ävrstih Äelika.
Tijekom oblikovanja metalnog lima dolazi do plastiÄnih deformacija
i nakon zavrÅ”enog procesa i vaÄenja izratka iz kalupa oblikovani lim
pokuÅ”ava zauzeti prethodni oblik pri Äemu se elastiÄno deformira. Ta
deformacija se naziva elastiÄan povrat. Poseban oblik elastiÄnog povrata
je negativni povrat. Ova pojava se može vidjeti kod savijanja u V-alatu uz
mali radijus vrha alata i malen kut žiga, Ŕto je pokazano u ovom radu
Under the Surface of Subcutaneous Adipose Tissue Biology
The global obesity epidemic enhanced contemporary interest in adipose tissue biology. Two structurally and functionally distinct depots, subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT), are spread throughout the body. Their distribution was recognized to be a major determinant of metabolic risk. Unlike VAT, SAT showed some protective endocrine and inflammatory features that might explain the occurrence of obese but metabolically healthy persons. The unique developmental gene expression signature, angiogenesis, and adipogenic potential of SAT determines its growth ability under the positive energy balance. The overflow hypothesis suggested that when SAT is unable to expand sufficiently, fat overflows towards metabolically adverse ectopic depots. Besides white adipose tissue, recent studies found important brown adipose tissue activity responsible for thermogenesis and energy dissipation in adults as well. SAT is prone to ābrowningā ā the appearance of particular beige adipocytes that contribute to its favorable metabolic effects. Morbid obesity, aging, hormonal status, nutrition, low physical activity, and other environmental factors impair SAT relative resistance to dysfunctional changes and promote development of metabolic disorders. The popular approach considering SAT mainly as the subject of cosmetic procedures for improving the appearance of body contours should be avoided. Complex heterogeneity of obesity revealed that a tissue of an extreme plasticity and rich interactions with vital functions of the body lies under the surface. Therapeutic manipulations to preserve and enhance healthier fat in order to correct obesity-related metabolic disorders seem to be a relevant but still unexplored opportunity.Ā </p
Application of Hydroforming Process in Sheet Metal Formation
This article deals with the theory and application of a hydroforming
process. Nowadays automobile manufacturers use high strength sheet
metal plates. This high strength steel sheet metal plates are strain hardened
in the process of metal forming. With the use of high strength steel, cars
are made lightweight, which is intended for low fuel consumption because
of high energy prices. Some examples of application of a hydroforming
process are simulated with FEM
Landslide inventory and characteristics, based on LiDAR scanning and optimised field investigations in the Kutina area, Croatia
This paper presents the preliminary results of analyses of landsliding processes derived from detailed LiDAR (Light Detection and Ranging) scans supported by field prospection on the south-western slopes of Mt. MoslavaÄka gora, in the wider Kutina area. This area is known for frequent landslides, but dedicated regional landslide research has not been previously undertaken.
High resolution LiDAR scanning and orthophoto imaging enabled the production of a reliable landslide inventory, but also enabled research on landslide properties and the morphology of the area. Field mapping and prospection, sampling and borehole coring assisted in the collection of information about the material characteristics and specific features of typical landslides. In the research area, which covers more than 71 km2, more than 1200 very small landslides were detected. The majority of landslides were discovered in just several geological units indicating their high susceptibility: Pleistocene silts and sands with clayey interlayers, followed by M2 silty sands and gravels, and M7 sands. Nearly half of the landslides are estimated to be of recent and younger age, while other landslides may be considered as being historical implying a ālong traditionā of landslide events in the research area. Preliminary terrain surface roughness analysis also supported the conclusion that the inventory contains landslides of several historical generations which are still detectable. In addition to slides (1123), this research also discovered numerous earthflow processes (143), which are more frequent in the predominantly sandy units.
The landslides in this area are largely located on the banks of the gullies and are directly related to the action of water. Regarding that situation and the engineering properties of the encountered geological units, four types of bank instabilities can be differentiated: slides on top of rock masses; slides in firm soil mixtures; landslides in sands; landslides in predominantly coherent soil complexes
Mineral assemblage and provenance of the Pliocene Viviparus beds from the Area of VukomeriÄke Gorice (Central Croatia)
Viviparus beds are sediments deposited in lacustrine and fluvial freshwater environments (Lake Slavonia) during the Pliocene and the earliest Pleistocene. A detailed field study and mineralogical, petrographic and chemical analyses were carried out to determine their composition and origin in the area of VukomeriÄke Gorice, Central Croatia. Viviparus beds are characterized by the vertical and lateral exchange of mineralogically and chemically mature pelites and sands. Pelitic sediments consist mainly of detrital quartz, calcite, dolomite and feldspar grains, with smectite as the most common clay mineral. Quartz and the most resistant lithic fragments dominate the sandy detritus. The composition of the sediments indicates their origin from the recycled orogen, while their textural immaturity suggests a short transport distance. Most of the material was re-deposited from the underlying Upper Miocene sediments, originally of Alpine provenance. A lesser proportion originated from Palaeogene sediments, Triassic carbonate rocks, basic or acidic magmatic rocks and metamorphites. The Medvednica and Žumberak Mts. were the most important source areas, while a smaller proportion of the material could have come from the MoslavaÄka gora Mt. and Banovina region. The uniform composition of the Viviparus beds over the entire vertical distribution of the sediments clearly indicates that the source areas did not change during their deposition. A significant change from the texturally and compositionally mature Upper Miocene clastic detritus of alpine origin, to the texturally immature material of the Viviparus beds of local origin is a consequence of compression and inversion of the previously extensional basin resulting in the uplifting and erosion of the mountains within the SW part of the Pannonian Basin System
Effect of spring-back in v-tool bending of high-strength steel sheet metal plates
This paper deals with the effects of technological parameters used in the V-die bending process, on the obtained product properties and dimensions. By variation of the tool geometry, several cases of steel sheet bending process are observed through the FEM simulations. Also by variation of different mechanical material properties, effects on product geometry are observed. Since the automobile manufacturers mostly use the high strength steel sheet metal plates, there is a need for the successful tool construction and optimization in order to produce quality products
Reprezentacije poluprostih Liejevih algebri
Cilj uvodnog dijela ovog rada je bio motivacija za prouÄavanje kako opÄenito Liejevih algebri tako i poluprostih Liejevih algebri. U tu svrhu uveden je pojam Liejeve grupe i izneseni su glavni rezultati o vezi Liejeve grupe sa pripadnom Liejevom algebrom. Eksplicitno je konstruiran funktor Lie koji Liejevoj grupi pridružuje Liejevu algebru. Zapravo, taj funktor uspostavlja ekvivalenciju izmeÄu 1-povezanih Liejevih grupa i konaÄnodimenzionalnih realnih Liejevih algebri. Dane su definicije svih pojmova važnih za ovaj rad: Liejeve algebre, reprezentacije, derivacije. Uvedene su i odreÄene važne klase ovih objekata poput rjeÅ”ive i poluproste Liejeve algebre, ireducibilne i potpuno reducibilne reprezentacije, unutarnjih derivacija. Nakon uvoÄenja pojmova dokazani su osnovni rezultati vezani uz Liejeve algebre i reprezentacije, najvažniji medu njima su Engelov teorem, Liejev teorem, Schurova lema i Cartanovi kriteriji rjeÅ”ivosti. Zatim su dana neka važna svojstva poluprostih Liejevih algebri i dokazan je kriterij poluprostote preko Killingove forme. Zatim je uveden pojam Casimirovog operatora reprezentacije i dokazana su njegova osnovna svojstva. Sve navedeno bila je priprema za dokaz fundamentalnog teorema u teoriji reprezentacija i Liejevih algebri, Weylovog teorema, koji kaže da je konaÄnodimenzionalna reprezentacija poluproste Liejeve algebre potpuno reducibilna. Nakon rezultata iz teorije navedeni su matriÄni primjeri Liejevih algebri i opisane su reprezentacije od koriÅ”tenjem Weylovog teorema.The purpose of the introductory part is the motivation to study Lie algebras and particularly semisimple Lie algebras. Therefore the concept of Lie group was introduced, as well as the main results about the close connection between the Lie group and its Lie algebra. We constructed a functor Lie taking Lie groups to Lie algebras. This functor in fact gives an equivalence between simply connected Lie groups and finite dimensional real Lie algebras. Most important definitions are given: Lie algebra, representation, derivation. Also, some important classes of these objects are introduced, like solvable and semisimple Lie algebras, irreducible and completely reducible representations, inner derivations. Afterwards the main results of the theory of Lie algebras and representations are given; the most important are certainly Engelās theorem, Lieās theorem, Schurās lemma and Cartanās solvability criteria. The main object in this study are semisimple Lie algebras, therefore some important properties of semisimple Lie algebras are given. Also, we got one crucial semisimplicity criterion using the Killing form. To get to the fundamental theorem of this study the concept of Casimir element is introduced and the main properties are proved. Afterwards we are ready to prove Weylās theorem, which states that any finite dimensional representation of a semisimple Lie algebra is completely reducible. After the theoretical part, some examples of Lie algebras are mentioned; these examples belong to matrix algebras. Also, using Weylās theorem all representations of are described
Reprezentacije poluprostih Liejevih algebri
Cilj uvodnog dijela ovog rada je bio motivacija za prouÄavanje kako opÄenito Liejevih algebri tako i poluprostih Liejevih algebri. U tu svrhu uveden je pojam Liejeve grupe i izneseni su glavni rezultati o vezi Liejeve grupe sa pripadnom Liejevom algebrom. Eksplicitno je konstruiran funktor Lie koji Liejevoj grupi pridružuje Liejevu algebru. Zapravo, taj funktor uspostavlja ekvivalenciju izmeÄu 1-povezanih Liejevih grupa i konaÄnodimenzionalnih realnih Liejevih algebri. Dane su definicije svih pojmova važnih za ovaj rad: Liejeve algebre, reprezentacije, derivacije. Uvedene su i odreÄene važne klase ovih objekata poput rjeÅ”ive i poluproste Liejeve algebre, ireducibilne i potpuno reducibilne reprezentacije, unutarnjih derivacija. Nakon uvoÄenja pojmova dokazani su osnovni rezultati vezani uz Liejeve algebre i reprezentacije, najvažniji medu njima su Engelov teorem, Liejev teorem, Schurova lema i Cartanovi kriteriji rjeÅ”ivosti. Zatim su dana neka važna svojstva poluprostih Liejevih algebri i dokazan je kriterij poluprostote preko Killingove forme. Zatim je uveden pojam Casimirovog operatora reprezentacije i dokazana su njegova osnovna svojstva. Sve navedeno bila je priprema za dokaz fundamentalnog teorema u teoriji reprezentacija i Liejevih algebri, Weylovog teorema, koji kaže da je konaÄnodimenzionalna reprezentacija poluproste Liejeve algebre potpuno reducibilna. Nakon rezultata iz teorije navedeni su matriÄni primjeri Liejevih algebri i opisane su reprezentacije od koriÅ”tenjem Weylovog teorema.The purpose of the introductory part is the motivation to study Lie algebras and particularly semisimple Lie algebras. Therefore the concept of Lie group was introduced, as well as the main results about the close connection between the Lie group and its Lie algebra. We constructed a functor Lie taking Lie groups to Lie algebras. This functor in fact gives an equivalence between simply connected Lie groups and finite dimensional real Lie algebras. Most important definitions are given: Lie algebra, representation, derivation. Also, some important classes of these objects are introduced, like solvable and semisimple Lie algebras, irreducible and completely reducible representations, inner derivations. Afterwards the main results of the theory of Lie algebras and representations are given; the most important are certainly Engelās theorem, Lieās theorem, Schurās lemma and Cartanās solvability criteria. The main object in this study are semisimple Lie algebras, therefore some important properties of semisimple Lie algebras are given. Also, we got one crucial semisimplicity criterion using the Killing form. To get to the fundamental theorem of this study the concept of Casimir element is introduced and the main properties are proved. Afterwards we are ready to prove Weylās theorem, which states that any finite dimensional representation of a semisimple Lie algebra is completely reducible. After the theoretical part, some examples of Lie algebras are mentioned; these examples belong to matrix algebras. Also, using Weylās theorem all representations of are described
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