Determination of optimum insulation thicknesses of the external walls and roof (ceiling) for Turkey's different degree-day regions

The external walls and roof of a building are the interface between its interior and the outdoor environment. Insulation of the external walls and roof is the most cost-effective way of controlling the outside elements to make homes more comfortable. Although insulation is generally accepted as a factor increasing the building costs, with the calculations we have shown that this is not the case. Fuel consumption and operational costs are reduced by increasing the thickness of the external walls and roof (ceiling), despite an increase in the investment costs. According to Turkish Standard Number 825 (TS 825), there are four different degree-day (DD) regions, and the required heat loads for the buildings in these regions exhibit large differences. Therefore, a method based on costs is needed for the determination of optimum insulation thicknesses of different DD regions. In this study, optimum insulation thicknesses for different DD regions of Turkey, namely, Izmir (DD: 1450), Bursa (DD: 2203), Eski?ehir (DD: 3215) and Erzurum (DD: 4856), have been determined for a lifetime of N years, maximizing the present worth value of annual energy savings for insulated external walls.     

An Intelligent Session Key-Based Hybrid Lightweight Image Encryption Algorithm Using Logistic-Tent Map and Crossover Operator for Internet of Multimedia Things

Due to the increasing demand for IoMT applications in numerous fields such as healthcare, smart city, smart grids, industrial internet, etc. The privacy and security become a major issue in front of various researchers working in this field. This work proposed a lightweight image encryption algorithm based on a logistic-tent map and crossover operator of a genetic algorithm. Various 1-D chaotic maps are discussed in the literature review, but in some cases, hybrid 1-D chaotic maps have higher performance than simple 1-D chaotic maps. So 1-D chaotic map along with a crossover operator is used in this work. Here logistic-tent map and crossover are used to generate the random session key for each image encryption. Also, a crossover operator is used in encryption rounds for increasing confusion and diffusion. Here in this work, for each image encryption, a new intelligent session key is generated. The strength of the proposed image cryptographic scheme is assessed against resistance to the differential attack (UACI and NPCR), statistical attack (histogram analysis, correlation coefficient and information entropy) and sensitivity to the secret key. The extensive experiments of performance and security assessment show that the proposed cryptographic image scheme is secure enough to withstand all potential cryptanalytic attacks.

     

Ultrafast Photo-Thermal Switching of Terahertz Spin Currents

Dissipationless and scattering-free spin-based terahertz electronics is the futuristic technology for energy-efficient information processing. Femtosecond light pulse provides an ideal pathway for exciting the ferromagnet (FM) out-of-equilibrium, causing ultrafast demagnetization and superdiffusive spin transport at sub-picosecond timescale, giving rise to transient terahertz radiation. Concomitantly, light pulses also deposit thermal energy at short timescales, suggesting the possibility of abrupt change in magnetic anisotropy of the FM that could cause ultrafast photo-thermal switching (PTS) of terahertz spin currents. Here, a single light pulse induced PTS of the terahertz spin current manifested through the phase reversal of the emitted terahertz photons is demonstrated. The switching of the transient spin current is due to the reversal of the magnetization state across the energy barrier of the FM layer. This demonstration opens a new paradigm for on-chip spintronic devices enabling ultralow-power hybrid electronics and photonics fueled by the interplay of charge, spin, thermal, and optical signals.     

Electrical and Pyroelectric Properties of K2Pb2Gd2W2Ti4Nb4O30 Ferroelectrics

A polycrystalline sample of K₂Pb₂Gd₂W₂Ti₄Nb₄O₃₀ was prepared by a high-temperature solid-state reaction method. The formation of the single-phase compound (at room temperature) was confirmed by preliminary x-ray structural analysis. The surface morphology recorded by scanning electron microscopy at room temperature exhibits a uniform grain distribution on the surface of the sample with few voids. Studies of the (i) variation of dielectric parameters with temperature (27°C to 430°C) and frequency (1 kHz to 5 MHz) and (ii) temperature dependence of polarization confirmed the existence of ferroelectricity in the material below the transition temperatures. Two dielectric anomalies observed at 304°C and 378°C suggest the existence of phase transitions in the material. The temperature and frequency dependences of electrical parameters of the material exhibit a strong correlation between microstructure and properties of the material. The temperature dependence of the direct-current (dc) conductivity shows the typical Arrhenius and negative temperature coefficient of resistance (NTCR) behavior of the material. The variation of the alternating-current (ac) conductivity with frequency obeys Jonscher’s universal power law. The current variation with temperature shows that the material has high pyroelectric coefficient and figure of merit, and thus it is useful for pyroelectric sensors. Even with a small piezoelectric coefficient (4.5 × 10^?12 C/N), the material is confirmed to be ferroelectric.     

Fatty acids of neutral and phospholipids of three endangered trout: Salmo trutta caspius Kessler, Salmo trutta labrax Pallas and Salmo trutta macrostigma Dumeril

Total (TL), neutral (NL) and phospholipid (PL) amounts and fatty acid (FA) composition of female Salmo trutta caspius, Salmo trutta labrax and Salmo trutta macrostigma were investigated during one year. Twenty-three FAs were identified in both NLs and PLs. The principal FAs of both fractions were palmitic acid in saturated fatty acid, oleic acid in monounsaturated fatty acid, docosahexaenoic acid (DHA) in n-3 polyunsaturated fatty acids (n-3 PUFAs) and linoleic acid in n-6 PUFAs. The highest values for TLs, NLs and PLs were found in winter. As a general trend, the highest n-3/n-6 ratios and eicosapentaenoic acid (EPA) + DHA amounts were found in the winter and this coincided with the lowest gonado-somatic index.     

AC and DC Conductivity Studies on Lead-Free Ceramics: Sr1–xCaxBi4Ti4O15(x = 0, 0.2, 0.4, 0.6, 0.8)

Sr_1–xCa_xBi₄Ti₄O₁₅ [x = 0, 0.2, 0.4, 0.6, 0.8] ceramics are synthesized by solid-state reactive technique. Structural analyses are done by x-ray diffraction data. Morphological studies were carried out by scanning electron microscope, and the data showed plate-like structures. To understand the conductivity mechanism, frequency and temperature dependency of AC and DC conductivity studies are carried out. The conductivity measurements are done using an impedance analyzer (Wayn–Kerr) in the temperature range 100–600°C. The frequency-dependent AC conductivity at different temperatures indicates that the conduction process follows the universal power law, and the hopping frequency shifts toward higher frequency side with increase in temperature, below which the conductivity is frequency independent. The variation of DC conductivity confirms that the ceramics exhibit negative temperature coefficient of resistance behavior at high temperature. DC conductivity values do not show any linearity with doping concentration; for a particular composition SCBT06, the DC conductivity was low.     

Structural,dielectric and electrical properties of a new tungsten bronze ferroelectric ceramics

The polycrystalline sample of Li₂Pb₂Nd₂W₂Ti₄Ta₄O₃₀ was prepared by a solid-state reaction technique. Room temperature X-ray structural analysis confirms the formation of a single phase compound. The morphology of the sintered sample recorded by scanning electron microscope exhibits a uniform grain distribution. Detailed studies of the nature of variation of dielectric constant, tangent loss and polarization with temperature and frequency confirmed the existence of ferroelectricity in the material. The temperature and frequency dependence of impedance parameters (impedance, modulus, etc.) of the material exhibits a strong correlation of its micro-structure (i.e., bulk, grain boundary, etc.). The nature of variation of pyroelectric-coefficient and current with temperature suggests that material has good pyroelectric properties useful for pyroelectric detector.     

Energy efficiency and building construction in India

The energy conservation has become an important issue in building design, it is logical to apply the principle of energy costing to building projects, and to look for ways to minimize the total energy consumed during their lifetime. Even though the total quantity of energy consumed in a building during its lifetime may be many times than that consumed in its construction, there are number of reasons why the energy use in the construction process, and in particular in the building materials used, should be treated as a matter of importance in looking for ways to minimize energy use in the built environment as a whole. In this paper the energy costs of alternative construction techniques using an optimization framework are assessed and compared. The techniques of construction evaluated in this paper are commonly used pucca techniques as well as low-cost construction techniques. Energy consumption and resource requirements due to the use of alternative techniques of construction for a representative room of size 3.5 m×3.5 m×3.14 m are evaluated. An assessment of the magnitude of energy consumption, if housing shortages have to be met, shows that a huge amount of energy would be consumed in housing sector alone. The associated levels of carbon dioxide emissions associated with this construction would also be prohibitively high. Finally the paper concludes with recommendations for structural changes in the energy and construction policy in India to minimize energy consumption in building construction.