Recently, the use of virtual reality has been spreading rapidly in many industrial fields, such as games and entertainment, and 360 • contents are widely used in various applications of the virtual reality (VR) market. The 360 • contents create a virtual space comparable to real scenes. Coupled with the rapid growth of the 360 • image/video field, many projection formats have been developed and published. However, the studies which identify the best format for a variety of applications are still limited. Therefore, it is desirable to evaluate the visual quality of the projection formats used in the current market, and the result of the evaluation can be used as an important consideration capable of providing 360 • VR service of better quality. Here, we propose a methodology for the subjective test and briefly present ten 360 • projection formats used in our experiment. The proposed methodology for the subjective test uses a combination of the Degradation Category Rating (DCR) and Pair Comparison methods. We performed the subjective test with 15 participants for each test step, the experimental setup for which followed the proposed methodology. The results show that the equirectangular projection format (best known and widely used format in most commercial products) did not give the highest quality. Hybrid equiangular cubemap and equatorial cylindrical projection gave the best quality compared with the other eight formats. Based on the results of the DCR, it is noted that different monitors (size and resolution) do not affect the ranking of 360 • image projection formats. Our work presents the ranking of ten published projection formats which is useful for identifying the best format for a future 360 • image standard. INDEX TERMS 360 • projection format, subjective evaluation, degradation category rating, pair comparison, 360 • image.

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The major energy sources that human are relying on are fossil fuel and it is exhausted day by day. Furthermore, exploition and usage of fossil fuel also bring in many negative impacts on environmental polution. Solid oxide fuel cell (SOFC) has been considerred as a potential solution for such environmental and energy problems. Seeking a facile, cost and time saving process to synthesize Ba doped LaMnO3 is very important for development of SOFC applications because it helps to reduce the cost of comercial SOFC. LaMnO3 doped with Ba is more cost effective than Sr doped LaMnO3 because less rare earth elements are used. At the same time, its conductivity is still good enough with an appropriate thermal expansion matched with those of other parts of SOFC based on ytrium stabilized zirconia (YSZ). In this paper, Ba doped LaMnO3 nanoparticles (LBMO), a promissing material for making cathode of SOFC, were prepared by microwave combustion method. This material has many advantages.  Effect of the amount fuel in the combustion reaction on the products was studied by various methods such as: X-ray diffraction measurement, scanning electron microscopy, energy dispersive X-ray spectroscopy. The results showed that each doping rate requires an appropriate amount of fuel to obtain pure and crystalline product. The obtained LBMO nanoparticles are crystallined in hexagonal phase at doping ratio of 0.2 and orthohombic phase at doping ratio of equal or larger than 0.3.

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