Sukhleen Bindra Narang

Comparative Dielectric Analysis of Co-Zr Doped M-Type Barium Hexaferrites BaCoxZrxFe(12-2x)O19 Prepared by Different Wet Chemical Routes

Samples of barium hexaferrites (BaCoxZrxFe(12-2x)O19) with varying molar concentration of Cobalt and Zirconium were synthesized successfully by three different wet chemical routes: Sol gel, Citrate and self-combustion. Dielectric constant, dielectric loss tangent and AC Conductivity measurements were carried out in the frequency range 20Hz–1MHz over Impedance analyzer. Dielectric constant and loss tangent variations are explained on the basis of Maxwell-Wagner interfacial polarization in accordance with Koops phenomenological theory. AC Conductivity varies in accordance to Jonscher law (σac = σdc + Aωn) and shows normal behavior shown by other ferrites. The observed behavior of these samples suggests that the materials are suitable for applications in microwave devices. Three wet chemical routes are compared and it can be concluded that samples synthesized by citrate method are showing higher dielectric constant, low loss and low conductivity, hence are better.

Low fire M-phase lithium based dielectric ceramics for microwave applications: A review (I)

ABSTRACT Microwave dielectric ceramics have been used for various applications such as wireless communications including mobile communications, local-area networks, ultra high speed local area networks, intelligent transport systems, satellite communications and consumer electronic products. The continuous trend towards portable, light weight and multifunctional electronic components has motivated scientists to enhance the properties of existing materials and develop new dielectric materials. During the past 3 decades, a lot of research has been taken place in this field. Various low fire systems having sintering temperature ≤1300°C like nickel-niobates, bismuth-niobates, bismuth-zinc-niobates, lithium-niobates and lithium-tantalates have been reported. However, the information on these useful materials is sprinkled. The main purpose of this review is to bring together the data on the low fire M-phase lithium based dielectric ceramics with remarkable dielectric properties. Sintering temperature of all the M-phase Li based solid solution has been reduced from 1100°C approximately to about (9000-850°C) with the help of sintering aids. It should be of great help to researchers and technologists across the globe.

Frequency and temperature dependence of dielectric and electric properties of Ba2-xSm4+2x/3Ti8O24 with structural analysis

Abstract Dielectric ceramics samples of barium titanium oxide doped with samarium, having a complex structural formula of Ba2-xSm4+2x/3Ti8O24 (referred to as BST), were fabricated by a high temperature solid-state reaction technique with varying x (0.0, 0.2, 0.4, 0.6). X-ray diffraction technique was used to check the formation of particular phases. Scanning electron microscope technique was used to study the surface morphology of the samples. The samples were studied in a temperature range of 298 K to 623 K and frequency range of 10 KHz to 1 MHz. The dielectric constant (εr), loss tangent (tan δ), and AC conductivity (σAC) were measured on sintered disks of BST samples. The DC resistivity of different compositions was measured at room temperature. Detailed studies of dielectric and electrical properties showed that these properties are strongly dependent on composition, frequency and temperature. The compounds showed stable behavior in lower temperature range (up to 523 K), therefore, they can be used in practical applications in this temperature range.

Complex permittivity, permeability and microwave absorbing properties of Co–Ti substituted strontium hexaferrite

Abstract M-type strontium ferrite with compositions SrFe(12-2x)CoxTixO19 (x = 0.0, 0.3, 0.5, 0.7, 1.0), were prepared by two route ceramic method. The effects of Co–Ti substitution on their microstructure, electromagnetic properties, and microwave absorptive behavior were analyzed. The complex permittivity (∊′-j∊″) and complex permeability (μ′-jμ″) have been measured from 8.2 to 12.4 GHz using a network analyzer. Scanning electron microscope was used to analyze the grain size distribution and porosity of the ferrite. X-ray diffraction confirmed the M-type structure of the doped strontium ferrite. Vibrating sample magnetometer was used to study hysteresis loop of the ferrite. This study suggests that the control of grain size, decrease in coercivity and enhanced values of dielectric constant and loss are effective means to improve microwave absorption. The dielectric constant and loss were enhanced in comparison to the permeability constant and loss over the entire frequency range.

Effect of Substitution of Samarium and Lanthanum on Dielectric and Electrical Properties of Barium Titanate

In this research paper, we report the dielectric and electric investigation of series of dielectric ceramics samples with structural formula Ba2-xRe4+2x/3Ti8O24 (where Re = Sm and La and x = 0.0, 0.2, 0.4 and 0.6). The dielectric parameters (i.e. dielectric constant and loss tangent) and ac conductivity are measured with impedance analyzer. This paper is presented to compare the effect of samarium and lanthanum doping on the properties of barium titanate. The research work concludes that lanthanum doping has more favorable effect on the properties. This paper also presents impedance analysis and V-I characteristics of all the samples. This is concluded that these properties are strongly dependent on frequency, temperature and composition. The investigation reports almost constant value of dielectric constant and very low loss tangent at lower temperatures.

Managing QoS degradation of partner web services: A proactive and preventive approach

In the service oriented paradigm, a software solution is a composition of individual web services. These web services, also called partner services, contribute not only to realize the functional capabilities of the software solution but also determine its Quality of Service (QoS). A partner web service operates in a dynamic environment, and hence is vulnerable to failures, or suffers from QoS degradation. The failure of a partner web service compromises QoS of service based solution. Therefore, a research challenge arises as to how to manage web services which suddenly disappear at the time of execution or stop performing as expected. Several solutions exist for run time monitoring of the partner web services so that when QoS values of some of them degrade, the software solution can be adapted and executed using alternative web services with better QoS. But these solutions are confined either to client side or to provider side. In this paper, we propose a solution which is distributed between the clients and the service providers. It is a software agent based framework that prevents invocation of partner web services with degraded QoS. The experimental results show the effectiveness and efficiency of the proposed solution in a dynamic runtime environment.

Particle Swarm Optimization Framework for Low Power Testing of VLSI Circuits

Power dissipation in sequential circuits is due to increased toggling count of Circuit under Test, which depends upon test vectors applied. If successive test vectors sequenceshave more toggling nature then it is sure that toggling rate of flip flops is higher. Higher toggling for flip flopsresults more power dissipation. To overcome this problem, one method is to use GA to have test vectors of high fault coverage in short interval, followed by Hamming distance management on test patterns. This approach is time consuming and needs more efforts. Another method which is purposed in this paper is a PSO based Frame Work to optimize power dissipation. Here target is to set the entire test vector in a frame for time period ‘T’, so that the frame consists of all those vectors strings which not only provide high fault coverage but also arrange vectors in frame to produce minimum toggling.

Energy harvesting using piezoelectric materials

ABSTRACT This paper is presented to achieve the objective of energy harvesting from vibrational sources through piezoelectric materials. In this analysis, two piezoelectric buzzers: 35 mm buzzer and 27 mm buzzer were used to carry out the experiment. The experimental set-up includes an electro-dynamic shaker, function generator and a power amplifier. Buzzer of thickness 35 mm gave maximum output at resonant frequency of 23 Hz and 57 g of mechanical stress while buzzer of thickness 27 mm gave maximum output at resonant frequency of 25 Hz and 27 g of weight. The paper also presents some important applications of piezoelectricity in day-to-day life.

Managing Availability of web services in service oriented systems

In real world Service Oriented Software Systems, changes to web services infrastructure are not an exception but a rule. Timely detection and a fast reaction to handle these changes are important to reduce the impact. This paper proposes an agent based framework to manage the situation when third party web services become unavailable. It uses the concept of mobile agents to monitor web services on the provider side. The framework is implemented using Advanced JAVA and JADE environment. Experimental analysis shows that the proposed solution is both effective and efficient. In future, the framework will be extended to include monitoring of other Quality of Service properties.

Modeling and Simulation of Efficient March Algorithm for Memory Testing

Semiconductor memories are considered one of the most important aspects of modern microelectronics. Memories are the most important universal components in SoC (System on Chip) today. Almost all SoC’s contain some type of embedded memories, such as ROM, RAM, DRAM and flash memory. Testing them becomes a challenge as these devices become more complex. The modeling and simulation of Memory BIST is presented in this paper. The architecture is implemented using Hardware Description Language and an area overhead is analyzed. The LR algorithm is implemented on to test the SRAM faults like stuck at faults, inversion coupling faults, linked faults etc.