Performance of a small‐scale compressed air storage (CAS)

The use of renewable energy, such as wind and solar, has significantly increased in the last decade. However, these renewable technologies have the limitation of being intermittent; thus, storing energy in the form of compressed air is a promising option. In compressed air energy storage (CAES), the electrical energy from the power network is transformed into a high‐pressure storage system through a compressor. Then, when the demand for electricity is high, the stored high‐pressure air is used to drive a turbine to generate electricity. The advantages of CAES are its high energy density and quality, and for being environmentally friendly process. In the existing facilities of University of Auckland, New Zealand, air cavern is not available; thus, a high‐pressure tank is used to store the compressed air, which could provide an excellent opportunity for small size applications. There is a limited literature available on the temperature and pressure profiles in a typical high‐pressure tank during charging and discharging processes. Therefore, this research investigates how temperature and pressure inside a high‐pressure tank change during charging and discharging processes. It will provide a better understanding for heat transfer in such system. Furthermore, it will provide the necessary information needed for the designing of an efficient small‐scale CAES. In this work, air is compressed to a maximum pressure of 200 bar and stored into a 2 L tank, which is fully fitted with a pressure transducer and a thermocouple suitable for high‐pressure measurements. The charging and discharging process is theoretically modeled, and the results are compared with the experimental measurements, showing a good agreement. The heat balance on the system is used to validate the steady‐state condition, while dynamic analysis is used to predict the transient change of compressed air and tank wall temperatures. The theoretical modeling is undertaken by solving the differential equations describing the transient change in temperature of both air and tank wall. The results of this study show that air temperature rises from 24°C to 60°C at 100 bar and from approximately 17°C to over 60°C at 200 bar. During discharging process, air temperature drops from ambient to 5°C at starting pressure of 100 bar and to ?20°C at starting pressure of 200 bar.     

Electrochemical and thermal properties of SmBa0.5Sr0.5Co2O5+δ cathode impregnated with Ce0.8Sm0.2O1.9 nanoparticles for intermediate-temperature solid oxide fuel cells

SmBa_0.5Sr_0.5Co₂O_5+δ (SBSC55) impregnated with nano-sized Ce_0.8Sm_0.2O_1.9 (SDC) powder has been investigated as a candidate cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The cathode chemical compatibility with electrolyte, thermal expansion behavior, and electrochemical performance are investigated. For compatibility, a good chemical compatibility between SBSC55 and SDC electrolyte is still kept at 1100 °C in air. For thermal dilation curve, it could be divided into two regions, one is the low temperature region (100–265 °C); the other is the high temperature region (265–850 °C). In the low temperature region (100–265 °C), a TEC value is about 17.0 × 10^?6 K^?1 and an increase in slope in the higher temperatures region (265–800 °C), in which a TEC value is around 21.1 × 10^?6 K^?1. There is an inflection region ranged from 225 to 330 °C in the curve of d(δL/L)/dT vs. temperature. The peak inflection point located about 265 °C is associated to the initial temperature for the loss of lattice oxygen and the formation of oxygen vacancies. For electrochemical properties, the polarization resistances (R_p) significantly reduced from 4.17 Ω cm² of pure SBSC55 to 1.28 Ω cm² of 0.65 mg cm^?2 of SDC-impregnated SBSC55 at 600 °C. The single cell performance of SBSC55∣SDC∣Ni-SDC loaded with 0.65 mg cm^?2 SDC exhibited the optimum power density of 823 mW cm^?2 at operating temperature of 800 °C. Based on above-mentioned properties, SBSC55 impregnated with an appropriate SDC is a potential cathode for IT-SOFCs.     

AFM Investigation of Mechanical Properties of Dentin

Mechanical properties of peritubular dentin were investigated using scanning probe microscopy techniques, namely Nanoindentation and Band Excitation. Particular attention was directed to the possible existence of a gradient in these properties moving outward from the tubular lumen to the junction with the intertubular dentin. Finite element analysis showed that the influence of the boundaries is small relative to the effects observed. Thus, these results strongly support the concept of a lowering of modulus and hardness from the tubular exterior to its periphery, which appear to correlate with graded changes in the mineral content.     

Cryptanalysis of Skipjack Reduced to 31 Rounds Using Impossible Differentials

In this paper we present a cryptanalytic technique, based on impossible differentials. We use it to show that recovering keys of Skipjack reduced from 32 to 31 rounds can be performed faster than exhaustive search. We also describe the Yoyo game (a tool that can be used against reduced-round Skipjack), and other properties of Skipjack.     

Degradation of 1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane (DDT) by brown-rot fungi

Twelve species of brown-rot fungi (BRF) have been investigated for their ability to degrade 1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane (DDT). In potato dextrose broth (PDB) medium, Gloeophyllum trabeum, Fomitopsis pinicola and Daedalea dickinsii showed a high ability to degrade DDT. 1,1-Dichloro-2,2-bis (4-chlorophenyl) ethane (DDD), 1,1-dichloro-2,2-bis (4-chlorophenyl) ethylene (DDE) and 4,4-dichlorobenzophenone (DBP) were detected as metabolic products of DDT degradation by G. trabeum in PDB medium. The DDT degradation pathway in G. trabeum is proposed, which differs from the proposed pathways in bacteria and other fungi, particularly in the transformation of DDE to DDD. On the other hand, DBP was not detected as a metabolic product of DDT degradation in FeSO(4)-deficient cultures of G. trabeum, whereas DDE and DDD were detected, indicating the involvement of an iron-dependent reaction. Only DBP was detected from DDT, DDE and DDD degradation via a chemical Fenton reaction under conditions similar to those in G. trabeum cultures. These compounds may be directly transformed to DBP via a Fenton reaction.     

Silane-Modified Graphene Oxide as a Compatibilizer and Reinforcing Nanoparticle for Immiscible PP/PA Blends

Graphene oxide (GO) and aminosilane (AS)-modified GO (GOAS) have been studied as possible compatibilizers for immiscible polyblends. Ideally, for localization of nanoparticles (NPs) at the interface, the thermodynamics of the constituents and mixing dynamics have to be tailored and controlled, respectively. Accordingly, a variety of oxidation levels (10%–40%) of GOs were prepared using Hummer's method and further modified by AS. Experimental results indicated that the GO goes through thermal reduction (above 200°C) during blending and reduced GO (rGO) is produced. The GOAS moderated the reduction reaction and stabilized the GO. The thermodynamic wetting coefficient of PP (polypropylene)/PA (polyamide)/rGOAS system was shown to drive the rGOAS from the PP phase to the blend's interface during time-controlled blending. The localization of the rGOAS at the interface resulted in significant enhancement of mechanical properties using only 2–3 wt% of rGOAS. Over 100% enhancement in strength, 40% enhancement in modulus, and 30% in toughness were shown, compared with neat PP/PA. Reduced GOAS and its location at the interface resulted in a third glass transition temperature (Tg), in addition to the PP and PA respective Tgs. Rheological percolation at 2–3 wt% rGOAS (20%) supports the localization of rGOAS at the interface. Storage moduli increase with interfacial tension, in accordance to the rheological models. POLYM. ENG. SCI., 60:180–191, 2020. © 2019 Society of Plastics Engineers