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1.
A new solution for shallow and deep tunnels by considering the gravitational loads
Mohammad Reza Zareifard, Ahmad Fahimifar, 2012, izvirni znanstveni članek

Opis: A new, elasto-plastic, analytical-numerical solution, considering the axial-symmetry condition, for a circular tunnel excavated in a strain-softening and Hoek–Brown rock mass is proposed. To examine the effect of initial stress variations, and also the boundary conditions at the ground surface, the formulations are derived for different directions around the tunnel. Furthermore, the effect of the weight of the plastic zone is taken into account in this regard. As the derived differential equations have no explicit analytical solutions for the plastic zone, the finite-difference method (FDM) is used in this study. On the other hand, analytical expressions are derived for the elastic zone. Several illustrative examples are given to demonstrate the performance of the proposed solution, and to examine the effect of various boundary conditions. It is concluded that the classic solutions, based on the hydrostatic far-field stress, and neglecting the effect of the boundary conditions at the ground surface, give applicable results for a wide range of practical problems. However, ignoring the weight of the plastic zone in the analyses can lead to large errors in the calculations.
Ključne besede: ground-response curve, elasto-plastic analysis, boundary condition, axial symmetry, gravitational loads
Objavljeno: 13.06.2018; Ogledov: 553; Prenosov: 58
.pdf Celotno besedilo (406,96 KB)
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2.
Modelling and analysis of thermal and stress loads in train disc brakes - braking from 250 km/h to standstill
Marko Reibenschuh, Grega Oder, Franc Čuš, Iztok Potrč, 2009, izvirni znanstveni članek

Opis: Thermal and stress analysis of disc brakes under specific loads (driving downhill and braking to a standstill) was calculated. The FEM (Finite Element Method) was used to carry out the analysis. The analysis dealt with centrifugal load for two cases of braking, braking to a standstill on a flat surface and braking downhill, maintaining constant speed and afterwards braking to a standstill. The main boundary condition in both cases was the entered heat flux on the braking surface of the disc and the force of the brake clamps. Two different discs were used, one brand new (unused) and one with permitted wearing.
Ključne besede: discs brake, temperature conditions, temeprature loads, locomotives, motor train set
Objavljeno: 31.05.2012; Ogledov: 1432; Prenosov: 34
URL Povezava na celotno besedilo

3.
Thermal post-impact behaviour of closed-cell cellular structures with fillers
Matej Vesenjak, Andreas Öchsner, Zoran Ren, 2007, izvirni znanstveni članek

Opis: The study describes the behavior of regular closed-cell cellular structure with gaseous fillers under impact conditions and consequent post-impact thermal conduction due to the compression of filler gas. Two dependent but different analyses types have been carried out for this purpose: (i) a strongly coupled fluid-structure interaction and (ii) a weakly coupled thermal- structural analysis. This paper describes the structural analyses of the closed-cell cellular structure under impact loading. The explicit code LS-DYNA was used to computationally determine the behavior of cellular structure under compressive dynamic loading, where one unit volume element of the cellular structure has been discretised with finite elements considering a simultaneous strongly coupled interaction with the gaseous pore filler. Closed-cell cellular structures with different relative densities and initial pore pressures have been considered. Computational simulations have shown that the gaseous filler influences the mechanical behavior of cellular structure regarding the loading type, relative density and type of the base material. It was determined that the filler's temperature significantly increases due to the compressive impact loading, which might influence the macroscopic behavior of the cellular structure.
Ključne besede: mechanics, cellular structures, closed cells, gas fillers, impact loading, fluid-structure interaction, dynamic loads, LS-DYNA, ANSYS CFX 10.0, computational simulations
Objavljeno: 31.05.2012; Ogledov: 1163; Prenosov: 25
URL Povezava na celotno besedilo

4.
The influence of thread twist on alterations in fibers` mechanucl properties
Andreja Rudolf, Jelka Geršak, 2006, izvirni znanstveni članek

Opis: In order to design high-quality threads, it is necessary to know the properties of threads and fibers, as well as the loadings and deformations which may occur during the sewing process. Thread properties depend on the mechanical properties of the fiber and the constructional parameters of the thread and its surface treatment, which directly influence sewing performance.The mechanical properties of a thread primarily depend on the fiber mechanical properties and the amount of twist. Knowledge of the thread dynamic loadings during the sewing process, depending on the number of turns and the lubrication method, is important for planning the required processing properties of the thread. This paper presents research into the influence of thread twist and the lubrication method on the mechanical properties and dynamic load of PES core-spun thread and its fibers. Research into the mechanical properties of the different twisted and surface treated threads, and separated fibers was carried out for this purpose. The influence of threaddynamic load during a sewing process was also researched regarding any alterations in the mechanical properties of the threads and separated fibers. Analyses of the results show that the amount of twist depends on the mechanical properties of the thread and its constituent fibers, whilst the method of surface treatment is based on the specific mechanical properties of the thread. A dynamic load causes greater or smaller thread deformations, which is reflected in changes in the thread and fiber mechanical properties. The occurred changes depend on dynamic load, amount of twist, and the lubrication method, which is confirmed with statistical analysis of the measured results.
Ključne besede: garment manufacturing, sewing, threads, textile fibres, surface treatment, dynamic loads, mechanical properties, amount of twist
Objavljeno: 30.05.2012; Ogledov: 1839; Prenosov: 26
URL Povezava na celotno besedilo

5.
RADIO-FREKVENČNA IDENTIFIKACIJA KOT INSTRUMENT OPTIMIZACIJE DOBAVNE VERIGE
Mario Malačič, 2009, diplomsko delo

Opis: V raziskovalnem delu smo predstavili edinstveno tehnologijo RFID (ang. Rario- Frequency Identification) in s pomočjo osnovnih strategij SCM (ang. Supply Chain Management) prikazali možne optimizacijske nastavke na nivoju celotne dobavne verige. RFID je splošen izraz, ki se uporablja za opis sistema, ki brezkontaktno, preko radijskih valov, transmitira identiteto objekta zapisano v obliki unikatne serijske številke. Koncept sistema RFID je zelo preprost. Sestavljata ga RFDI bralnik z anteno in RFID priponka (ang. TAG) z anteno, prenosni medij med čitalnikom in priponko pa so radijski valovi nizke moči. Omrežje EPC pomaga implementirati tehnologijo RFID v odprte sisteme in na ta način doseči integracijo celotne dobavne verige v enoten sistem. S pomočjo online povezave želimo na nivoju posameznega izdelka, označenega z RFID odzivniki, doseči tako imenovani »internet stvari«. Virtualni prostor, v katerem bodo imeli predmeti določeno umetno inteligenco, kar bo omogočalo komunikacijo med predmeti, predmeti in stroji, stroji in ljudmi ter predmeti in ljudmi. Področja uporabe RFID so praktično neomejena. Trenutno se RFID uporablja za označevanje in sledenje živali, prepoznavanje izdelkov v trgovinah, identificiranje ladijskih kontejnerjev, plačilo cestnine, spremljanje pošiljk v logistiki, pri izposoji knjig v knjižnicah, na parkiriščih in v garažah, za kodiranje ključev itn. Tehnologija RFID v primerjavi s črtno kodo omogoča hitrejše in natančnejše logistične procese, kar bo imelo za posledico, da RFID čez čas izpodrine uporabo črtne kode. Zelo pomembna tema pri tehnologiji RFID je standardizacija, kajti ta zagotavlja globalno povezljivost komponent sistemov RFID, ki bodo v skladu s svetovnimi regulacijami, kar je izrednega pomena pri uporabi v globalnih dobavnih verigah. V nadaljevanju smo predstavili šest osnovnih strategij SCM, ki lahko v sinergiji s tehnologijo RFID na nivoju celotne dobavne verige dosega optimizacijske potenciale. Tako smo celotno dobavno verigo razdelili na štiri sklope, kjer smo za vsak posamezni odsek preučili kake prednosti prinaša implementacija nove tehnologije. Z uvedbo nove tehnologije so povezani določeni riziki. Varstvo podatkov predstavlja poglavitnega, ki skuša obvarovati posameznega potrošnika pred zlorabo njegovih podatkov. Veliki trgovski giganti, kot so Metro, Wall Mart in Tesco uporabljajo RFID že nekaj let. Oni predstavljajo gonilno silo pri širjenju uporabe tehnologije in posredno pri zniževanju cen odzivnikov, strojne ter programske opreme. Tehnologija je trenutno predraga za majhna in srednje velika podjetja, ki pa bodo morala v prihodnosti začeti razmišljati o njeni implementaciji, kajti konkurenca z dneva v dan postaja močnejša.
Ključne besede: RFID, črtna koda, Efficient Consumer Response, Supply Chain Management, Cross Docking, Efficient Administration, Efficient Unit Loads, Vendor Managed Inventory, Computer Assisted Ordering, Efficient Replenishment.
Objavljeno: 24.09.2009; Ogledov: 2096; Prenosov: 252
.pdf Celotno besedilo (850,80 KB)

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