Analysis of a passive cooled building for the semiarid climate

The quasi-steady-state analysis of a hostel building for semiarid climatic conditions has been presented by incorporating the effectiveness of various cooling approaches in the analysis. The effect of intermittent use of an exhaust chimney, opening of windows and a desert cooler has also been incorporated in the analysis to study its performance. It is observed that there is an appreciable reduction in the room temperature by intermittent use of various cooling approaches.     

On the decidability of sparse univariate polynomial interpolation

We consider the problem of determining whether or not there exists a sparse univariate polynomial that interpolates a given setS={(x _i ,y _i )} of points. Several important cases are resolved, e.g., the case when thex _i's are all positive rational numbers. But the general problem remains open.     

Freestanding 3D Graphene–Nickel Encapsulated Nitrogen‐Rich Aligned Bamboo Like Carbon Nanotubes for High‐Performance Supercapacitors with Robust Cycle Stability

3D hierarchical structures are reported based on graphene–nickel encapsulated nitrogen‐rich aligned bamboo like carbon nanotubes, which show not only high‐performance supercapacitance behavior but also a great robust cyclic stability. A facile synthesis route is developed of 2D nickel oxide decorated functionalized graphene nanosheets (2D‐NiO‐f:GNSs) hybrids and 3D nitrogen doped bamboo‐shaped carbon nanotubes (NCNTs) vertically standing on the functionalized graphene nanosheets (3D‐NCNT@f:GNSs) by using a thermal decomposition method. The chemical reduction and morphology‐dependent electrochemical response are investigated. The enhanced specific capacitance of 3D‐NCNT@f:GNSs as compared to that of 2D‐NiO‐f:GNSs suggests the synergistic effects and indicates the importance of energy storage and superior long‐term cycling performance that are achieved. This 3D‐NCNT@f:GNSs hybrid shows a remarkable cycling stability with a maximum power density of 12.32 kW kg⁻¹ and maximum energy density of 109.13 Wh kg⁻¹ due to the good connection of NCNT and f:GNSs. This unique 3D nano network architecture enables the availability of large surface areas of NCNT, thus endowing the nanohybrids with high specific capacitance and excellent reusability.     

Interplay Between Superconductivity and Antiferromagnetism in HoNi2B2C

A microscopic theory of interplay between superconductivity and antiferromagnetism in rare-earth nickel boride, HoNi₂B₂C is developed from first principles. Self-consistent equations for the superconducting order parameter Δ and magnetic order parameter Γ are derived using a Green’s function technique and an equation of motion method. The theory is applied to explain the experimental results in the antiferromagnetic superconductor HoNi₂B₂C. The present model explains the true coexistence of superconductivity and antiferromagnetism in this system. The behavior of the superconducting order parameter (Δ), the magnetic order parameter (Γ), the specific heat, the density of states, the free energy and critical field (H _c) is also studied for the system HoNi₂B₂C. Distinct features of the coexistence region are discussed. There is the convincing evidence that the theory is fully compatible with the key experiments.     

A review of information flow diagrammatic models for product–service systems

Quality of an assembly of any manufactured product is mainly based on the quality of mating components. Due to random variations in sources such as materials, machines, operators, and measurements, mating components manufactured by even the same process may vary in their dimensions. When mating components are assembled linearly, the resulting assembly tolerance will be the sum of the mating components tolerances. All precision assemblies demand for a closer assembly tolerance. A significant amount of research has already been done to minimize assembly variation using selective assembly, when the dimensions of components follow normal distribution. However, in reality, the dimensions of components produced especially in smaller to medium size batches, invariably have some skewness (non-normality), which makes the methods developed and reported in the literature, often not suitable for practice. In this work, batch selective assembly methodology is proposed for components having non-normal distributions to minimize the assembly tolerance variations. The proposed method which employs a genetic algorithm for obtaining the best combination of mating components is able to achieve minimum variations in assembly tolerances and also maximum number of acceptable assemblies. The proposed algorithm is tested with a set of experimental problem datasets and is found outperforming the other existing methods found in the literature, in producing solutions with minimum assembly variation.     

Role of Nano-YbF3-Treated Carbon Fabric on Improving Abrasive Wear Performance of Polyetherimide Composites

A method for surface treatment of carbon fabric with nano-particles of rare earth salt (ytterbium fluoride–YbF₃) was tried first time in the authors’ laboratory to enhance the fiber–matrix interface, and has been reported here. In this article authors have reported on the performance evaluation of composites developed from the four fabrics treated with various doses viz. 0, 0.1, 0.3, and 0.5 wt% of YbF₃. The abrasive wear performance of these composites was evaluated by abrading the composites against silicon carbide abrasive paper under varying loads. The treated fabric composites exhibited lower coefficient of friction and higher wear resistance as compared with untreated fabric composite. A linear correlation between ILSS (interlaminar shear strength) and wear resistance was observed. Both were the highest for 0.3% dosing of fabric. Since it was also desirable to compare the efficiency of this novel method of treatment of carbon fibers with conventional one, a few results of composites with plasma-treated carbon fabric were compared with the nano-particle-treated fabric composites. It was concluded that the latest method improved the abrasive wear resistance of composites almost two times more than the plasma-treated composites. Fiber–matrix interface was strengthened because of the treatment as observed from SEM studies, ILSS, and matrix pick-up studies. Increased roughness of fiber surface was observed in topographical analysis by SEM. Effect of treatment on fiber was also observed by adhesion test and fiber tow tension test. SEM studies of worn surfaces were performed to understand wear mechanisms.     

Parametric study of various configurations of hybrid PV/thermal air collector: Experimental validation of theoretical model

In this paper, an attempt has been made to evaluate the overall performance of hybrid PV/thermal (PV/T) air collector. The different configurations of hybrid air collectors which are considered as unglazed and glazed PV/T air heaters, with and without tedlar. Analytical expressions for the temperatures of solar cells, back surface of the module, outlet air and the rate of extraction of useful thermal energy from hybrid PV/T air collectors have been derived. Further an analytical expression similar to Hottel–Whiller–Bliss (HWB) equation for flat plate collector has also been derived in terms of design and climatic parameters. Numerical computations have been carried out for composite climate of New Delhi and the results for different configurations have been compared. The thermal model for unglazed PV/T air heating system has also been validated experimentally for summer climatic conditions. It is observed that glazed hybrid PV/T without tedlar gives the best performance.     

Analytical expression for thermal efficiency of a passive solar still

Using energy balance equations for the different components of a passive solar still (namely, glass cover, water mass and basin liner), the effect on its thermal efficiency of water flowing over the glass cover with uniform velocity has been studied analytically. The efficiency is found to increase due to the water flow at higher depths of water in the basin. The result is validated by the experimental results of other authors.     

Parametric study of a reverse flat plate absorber cabinet dryer: A new concept

In this communication, the concept of reverse flat plate collector has been used as a heating medium of air for the drying of agricultural products in a cabinet dryer. The reverse flat plate absorber is a non-concentrating collector which can collect solar heat at high temperature unlike conventional nonconcentrating collectors. The thermal performance of the proposed dryer is analyzed by solving the various energy balance equations. An attempt has been made to optimize the vent area of the dryer for speedy flow of humid air from the drying chamber to the atmosphere. In order to have parametric studies, numerical computations have been carried out for a typical day in June for Delhi climatic conditions. The performance of this system is compared with that of conventional cabinet dryers. It is found that the reverse flat plate absorber dryer gives the better performance.