Thermophysical characteristics and application of metallic-oxide based mono and hybrid nanocomposite phase change materials for thermal management systems

This experimental study covers the chemical, physical, thermal characterization and application of novel nanocomposite phase change materials (NCPCMs) dispersed by TiO2, Al2O3, and CuO nanoparticles for thermal management systems. A commercial-grade of paraffin, namely RT-35HC, was considered as a phase change material (PCM). The mono and hybrid NCPCMs were synthesized at a constant weight concentration of 1.0 wt.. In the first phase, various characterization techniques were used to explore the thermophysical properties and chemical interaction of mono and hybrid NCPCMs. In the second phase, the thermal cooling performance was investigated by filling the prepared NCPCMs in a heat sink at various input power levels. The results showed the uniform dispersion of TiO2, Al2O3, and CuO nanoparticles onto the surface of both mono and hybrid NCPCMs without altering the chemical structure of RT-35HC. The optimum latent-heat of fusion and highest thermal conductivity of 228.46 J/g and 0.328 W/m K were obtained, respectively, of Al2OCuO dispersed hybrid NCPCM compared to pure RT-35HC. In comparison of RT-35HC, the increasing trend in specific heat capacity was observed of NCPCMs and 36.47% enhancement was obtained for hybrid NCPCM in solid-phase. The reduction in heat sink base temperature was achieved of 3.67%, 6.13%, 13.95% and 8.23% for NCPCM, NCPCM, NCPCM and NCPCM, respectively, compared to RT-35HC. Further, no phase segregation, less subcooling, smaller phase transition temperature, higher chemical and thermal stability were observed with hybrid NCPCMs which can be used potentially for thermal management of electronic devices, Li-ion batteries and photovoltaic (PV) modules systems

Spiritual quotient and ethical values towards organizational sustainability

During the last decade, many organizations were collapsed and had damage their organizational sustainability reason being severe ethical crisis. One of the main reasons affecting organizational sustainability is unethical behavior in the organization. Therefore, the question arises, how this grave issue of unethical behavior of employees can be solved? This paper seeks to assess if spiritual quotient (Here after SQ) is a solution to the unethical behavior of employees and how this SQ along with ethical values can contribute towards organizational sustainability. The paper concludes that SQ is the ultimate intelligence with which people address and solve the problems associated with meaning and value. It is the intelligence that has the force to help people use their actions and lives in a wider, richer and meaning-giving context. Moreover, promoting the ethical values, most of the organizations focus on ethics training programs aimed at increasing employee’s ethical behavior in organization. Thus, the paper finally suggests that employee unethical behavior in an organization can be solved through SQ and ethical values in organization

Research fatigue among injecting drug users in Karachi, Pakistan

Background Karachi is the largest metropolis of Pakistan and its economic hub attracting domestic migrants for economic opportunities. It is also the epicenter of HIV epidemic in the country. Since 2004, one pilot study and four behavioral and biological surveillance rounds have been conducted in Karachi. In addition many student research projects have also focused on key risk groups including injection drug users (IDUs). As a result of this extra ordinary exposure of same kind of questions, IDUs know how to respond to high value questions related to sharing of needles or unsafe sexual practices. The purpose of the study was to explore the element of research fatigue among IDUs in Karachi, Pakistan. Methods The study was conducted on 32 spots in Karachi, selected on the basis of estimate of IDUs at each spot. A trained field worker (recovered IDU) visited each spot; observed sharing behavior of IDUs and asked questions related to practices in January 2009. Verbal consent was obtained from each respondent before asking questions. Results On average 14 IDUs were present at each spot and out of 32 selected spots, 81% were active while more than two groups were present at 69% spots. In each group three to four IDUs were present and everyone in the group was sharing. One dose of injecting narcotics was observed. Sharing of syringes, needles and distilled water was observed at 63% spots while professional injector/street doctor was present at 60% spots. Conclusion There is a need to check internal consistency in surveillance research. It is highly likely that IDUs and other risk groups know how to respond to key questions but their responses do not match with the practices

The micro‐/nano‐PCMs for thermal energy storage systems: A state of art review

With advancement in technology, the nanotechnology, various thermal energy storage (TES) materials have been invented and modified with promising thermal transport properties. The solid–liquid phase change materials (PCMs) have been extensively used as TES materials for various energy applications due to their highly favourable and potential thermal properties. The class of PCMs, organic phase change materials (OPCMs) have more potential and advantages over the class, inorganic phase change materials (IPCMs) having high phase change enthalpy (positive advantage). However, the OPCMs possess low thermal conductivity as well as density and suffer leakage during the melting phase. The encapsulation technologies (i.e. micro and nano) of PCMs, with organic and inorganic materials, have a tendency to enhance the thermal conductivity, effective heat transfer, and leakage issues as TES materials. The encapsulation of PCMs involves several technologies to develop at both micro and nano levels, called micro–encapsulated PCMs (micro–PCM) and nano–encapsulated PCMs (nano–PCM) respectively. This study covers a wide range of preparation methods, thermal and morphological characteristics, their stability, applications and future perspective of micro/nano–PCMs as TES materials. The potential applications such as solar–to–thermal, electrical–to–thermal, thermal management, building, textile, foam, medical industry of micro– and nano–PCMs are reviewed critically. Finally, this review paper highlights the emerging future research paths of the mico/nano–PCMs for the researchers who are working in the area of thermal energy storage

A review on graphene based nanofluids: preparation, characterization and applications

A wide range of heat transfer systems require efficient heat transfer management from source to sink and vice versa. Over the last decade, graphene nanoparticles, matrix nanofluids have been one of the most investigated nanoparticles for a wide range of engineering applications. Graphene–based nanoparticles have several advantages over other nanoparticles: high stability, high thermal conductivity, low erosion and corrosion, and higher carrier mobility. Graphene–based nanofluids have found applications such as heat transfer, defect sensor, anti–infection therapy, energy harvesting systems, biomedical and cosmetics. With advancement of technology, more compact and efficient cooling media are needed to ensure efficiency and reliability of engineering systems and devices. This research study reports an overview of experimental and numerical investigations of graphene nanometer–sized particles with different base host fluids for major engineering applications of energy transfer systems and further thermophysical properties of graphene nanofluids

Heat Transfer Applications of TiO2 Nanofluids

To achieve acme heat transfer is our main disquiet in many heat transfer applications such as radiators, heat sinks and heat exchangers. Due to furtherance in technology, requirement for efficient systems have increased. Usually cooling medium used in these applications is liquid which carries away heat from system. Liquids have poor thermal conductivity as compared to solids. In order to improve the efficiency of system, cooling medium with high thermal conductivity should be used. Quest to improve thermal conductivity leads to usage of different methods, and one of them is addition of nanoparticles to base liquid. Application of nanofluids (a mixture of nanoparticles and base fluid) showed enhancement in heat transfer rate, which is not possible to achieve by using simple liquids. Different researchers used TiO2 nanoparticles in different heat transfer applications to observe the effects. Addition of titanium oxide nanoparticles into base fluid showed improvement in the thermal conductivity of fluid. This chapter will give an overview of usage of titanium oxide nanoparticles in numerous heat transfer applications

Knowledge Management and Sustainable Firms Growth: An Evidence from SMEs Sector of Pakistan

The main drive for this research was to investigate the relationship between knowledge management (KM) and sustainable firms’ growth in SMEs sector of Pakistan. Moreover, the research examined the mediating role of product and process innovations on the association of knowledge management and sustainable firms’ growth. A self-administered survey was structured and employed to gather the data from 218 garments related SMEs. The study employed SEM to measure direct and indirect effects. Findings of the study indicates that knowledge management has a positive and significant influence over sustainable firms’ growth while both product and process innovations significantly mediated the knowledge management and sustainable firms growth relationship. Current research findings offer valuable implications concerning the importance of KM in enhancing and facilitating process and product innovations for sustainable firms’ growth. This is a pioneer study for employing a unified model that illustrates the relationships among multiple variables pertaining to KM

Performance improvement in polymer electrolytic membrane fuel cell based on nonlinear control strategies—A comprehensive study

A Polymer Electrolytic Membrane Fuel Cell (PEMFC) is an efficient power device for automobiles, but its efficiency and life span depend upon its air delivery system. To ensure improved performance of PEMFC, the air delivery system must ensure proper regulation of Oxygen Excess Ratio (OER). This paper proposes two nonlinear control strategies, namely Integral Sliding Mode Control (ISMC) and Fast Terminal ISMC (FTISMC). Both the controllers are designed to control the OER at a constant level under load disturbances while avoiding oxygen starvation. The derived controllers are implemented in MATLAB/ Simulink. The corresponding simulation results depict that FTISMC has faster tracking performance and lesser fluctuations due to load disturbances in output net power, stack voltage/power, error tracking, OER, and compressor motor voltage. Lesser fluctuations in these parameters ensure increased efficiency and thus extended life of a PEMFC. The results are also compared with super twisting algorithm STA to show the effectiveness of the proposed techniques. ISMC and FTISMC yield 7% and 20% improved performance as compared to STA. The proposed research finds potential applications in hydrogen-powered fuel cell electric vehicles

Neural network and URED observer based fast terminal integral sliding mode control for energy efficient polymer electrolyte membrane fuel cell used in vehicular technologies

In this research work, a Neural Network (NN) and Uniform Robust Exact Differentiator (URED) observer-based Fast Terminal Integral Sliding Mode Control (FTISMC) has been proposed for Oxygen Excess Ratio (OER) regulation of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) power systems for vehicular applications. The controller uses URED as an observer for supply manifold pressure estimation. NN is used to estimate the stack temperature which is unavailable. The suggested control method increased the PEMFC's effectiveness and durability while demonstrating the finite-time convergence of system trajectories. By controlling the air-delivery system in the presence of uncertain current requirements and measurement noise, the approach ensures maximum power efficiency. The Lyapunov stability theorem has been used to confirm the stability of the presented algorithm. In addition, the suggested method eliminated the chattering phenomenon and improved power efficiency. Given these noteworthy characteristics, the research has the potential to decrease sensor dependence and production costs while also improving the transient and steady-state response in vehicular applications

In vitro Anti-ulcer potential of Raphanus sativus L. seeds

Background: Raphanus sativus L. is an indigenous plant that is traditionally used to treat peptic ulcer. Objective: This study assessed anti- Helicobacter pylori, antioxidant, and anti-urease activities of R. sativus seeds. Methods: this study targeted in-vitro model. The antioxidant activity of the methanol extract and n-butanol, aqueous, n- hexane and chloroform fractions of R. sativus seeds was determined using DPPH. Moreover, the inhibitory effects of the extract and fractions on the activity of urease and antibacterial activity against Helicobacter pylori were also evaluated. Results: The crude extract as well as its derived n-butanol fraction exhibited higher (IC50: 45 and 31 µg/mL respectively) DPPH inhibition activity and inhibition of urease (IC50: 75.0 and 55.9 µg/mL respectively) while aqueous extract inhibited H. pylori strongly (MIC50: 15 µg/mL). Conclusion: Collectively, our data show that R. sativus extract and fractions possess antioxidant, anti- H. pylori and anti-urease potential. The traditional uses of R. sativus as anti-ulcer, might be due to its anti-urease activity