Review on sheet metal forming process of aluminium alloys

The application of aluminum alloys in automotive and aerospace industries has been growing significantly in the last 20 years. Due to their high specific strength, aluminum became a strong replacement for steel particularly at automotive manufacturing. However, to deform a complex panel part from aluminum is quite challenging specifically at cold forming condition in which the formability is quite low. Many attempts have been processed to improve the formability problem of the aluminum alloy such warm forming, hot forming, superplastic forming and Hot forming and cold die quench (HFQ) processes. This paper presents a critical survey for different forming methods and identifying the advantages and drawbacks for each method. This review will help researcher to be familiar about the history, development and state of art of metal forming processes of aluminum sheet alloys

A sufficient condition on the existence of pure equilibrium in two-person symmetric zerosum games

In this note, we introduce a new sufficient condition, called sign-quasiconcavity, on the existence of a pure equilibrium in two-person symmetric zerosum games, which generalizes both generalized ordinal potentials (Monderer and Shapley, 1996) and quasiconcavity (Duerschet al., 2012)

Maximin equilibrium

We introduce a new concept which extends von Neumann and Morgenstern's maximin strategy solution by incorporating 'individual rationality' of the players. Maximin equilibrium, extending Nash's value approach, is based on the evaluation of the strategic uncertainty of the whole game. We show that maximin equilibrium is invariant under strictly increasing transformations of the payoffs. Notably, every finite game possesses a maximin equilibrium in pure strategies. Considering the games in von Neumann-Morgenstern mixed extension, we demonstrate that the maximin equilibrium value is precisely the maximin (minimax) value and it coincides with the maximin strategies in twoperson zerosum games. We also show that for every Nash equilibrium that is not a maximin equilibrium there exists a maximin equilibrium that Pareto dominates it. Hence, a strong Nash equilibrium is always a maximin equilibrium. In addition, a maximin equilibrium is never Pareto dominated by a Nash equilibrium. Finally, we discuss maximin equilibrium predictions in several games including the traveler's dilemma

A paradox of rationality à la von Neumann-Morgenstern

We show that there are games and decision situations in which it is not possible for the decision maker to be rational a la von Neumann-Morgenstern in both situations simultaneously, which is the source of the paradox presented in this note. We provide an assumption which is the necessary and sufficient condition for a decision maker to be rational in both situations

Comparative study of conventional and unconventional designs of cathode flow fields in PEM fuel cell

The choice of an appropriate flow field distributor is crucial to circumvent mass and charge transfer resistance-related issues in proton exchange membrane fuel cells (PEMFCs). In this work, incorporating all the anisotropic nature of the gas diffusion layers (GDLs), a three-dimensional, multiphase CFD model is built to perform a comparative study of several types of cathode flow field designs. Three conventional (i.e. parallel, serpentine and interdigitated) and two recently-introduced (i.e. parallel with blocks and the metal foam) flow field designs were considered for the cathode side. The results showed that the best fuel cell performance is obtained with the metal foam flow field as it induces the lowest water saturation, the lowest values and more uniform distribution of current density and temperature as well as relatively medium pressure drop. Compared with the parallel flow field case, the peak power density increases by about 50% when using the metal foam flow field and by about 10% when using the other three investigated flow fields (i.e. serpentine, interdigitated and parallel with blocks). The parametric analysis reveals that the metal foam outperforms other designs at intermediate and high humidity conditions whereas the interdigitated flow field design outperforms other designs at low humidity conditions

Histological observation of Gelam (Melaleuca cajuputi Powell) in different ecosystems of Terengganu

A histological and anatomical comparative analysis of Gelam, Melaleuca cajuputi Powell was conducted to determine the adaptability Gelam (Melaleuca cajuputi Powell, Family = Myrtaceae) in two different micro-ecosystems of Terengganu. The sites sampling chosen were Jambu Bongkok Amenity Forest (Formerly known as Rantau Abang Amenity Forest), a large swamp forests and prominent flooding site in the  District of Marang, Terengganu and Taman Penyelidikan Alam, Bukit Kor  - a hard top soil area of Marang, Terengganu. The objective of this study is to compare the anatomy and histology features of gelam in these two areas. Results show that gelam from both ecosystems exhibits  morphological differences and variations in some tissues (in leaf, petiole, bark, and root anatomy such as in type of epicuticular waxes, bark anatomy, leaf anatomy, vascular bundle, bark fibre pits, vessel, phloem, xylem, cortex, epidermal cells and mesophyll cells). This initial observation may suggest that gelam can adapt well in different ecosystems of Terengganu. Its ability to response well toward Terengganu’s different coastal environmental changes could make gelam a viable tree for conservation and landscape program. Keywords: Melaleuca cajuputi Powell, Gelam; anatomy; histology; microscopy; Terenggan

N-doped TiO2 synthesised via microwave induced photocatalytic on RR4 dye removal under LED light irradiation

Nitrogen doped titanium dioxide (N-doped TiO2) was synthesized by microwave using urea as nitrogen sources with commercially available TiO2-P25. The N-doped TiO2 was compared with unmodified TiO2 by carrying out the investigation on its properties using x-ray diffraction (XRD) analysis, Brunauer-Emmett-Teller (BET), Fourier transformed infrared spectroscopy (FTIR) and diffuse reflectance spectroscopy (UV-Vis DRS). The photocatalytic activities of N-doped TiO2 and unmodified TiO2 were studied for photodegradation of reactive red 4 (RR4) under light emitting diode (LED) light irradiation. An active photoresponse under LED light irradiation was observed from N-doped TiO2 with 60 min of time irradiation to complete RR4 color removal while no photocatalytic degradation was observed from unmodified

Metal-Free Nitrogen-Doped Carbon Foam Electrocatalysts for the Oxygen Reduction Reaction in Acid Solution

Metal-free, nitrogen-doped carbon foam is utilized as a model non-precious electrocatalyst system to investigate the role of nitrogen in the oxygen reduction reaction (ORR) in the absence of iron contamination. This graphene-like foam displays relatively high activity for the ORR in acid, despite being proven free from transition-metal impurities. The onset potential is 0.85 VRHE, the mass activity is 2.8 A/g at 0.6 VRHE, and the current density is −4.0 mA/cm2. The maximum electron transfer number is calculated to be 3.6, revealing that a 4-electron pathway is possible in nitrogen-doped carbon, even in the absence of transition-metal coordination sites. The excellent electrochemical activity is attributed to the large surface area (700 m2/g), improved conductivity after graphitization, and the relatively high proportion of tertiary (graphite-like) nitrogen

Density of States Extracted from Modified Recursion Relations

We evaluate the density of states (DOS) associated with tridiagonal symmetric Hamiltonian matrices and study the effect of perturbation on one of its entries. Analysis is carried out by studying the resulting three-term recursion relation and the corresponding orthogonal polynomials of the first and second kind. We found closed form expressions for the new DOS in terms of the original one when perturbation affects a single diagonal or off-diagonal site or a combination of both. The projected DOS is also calculated numerically and its relation to the average DOS is explored both analytically and numerically.Comment: 15 pages including 8 figures (one in color