A note on the correct evaluation of junction capacitance of a solar cell

In the fabrication of low-cost solar cells one has often to contend with finite series and shunt resistances. These tend to give misleading values of the junction capacitance as measured with an ordinary bridge. The problem is discussed analytically and graphical plots are given for determination of the true values from the measured ones. Practical use of these plots is discussed and illustrated with the help of experiments on thin-film Cu₂S-CdS solar cells.     

ADI Method for Heat Conduction Problems in an Orthogonal Coordinate System

A mathematical model has been developed for the time-dependent heat conduction process in a region of arbitrary geometry. An alternating direction implicit (ADI) scheme has been worked out for the computer solution of the problem in three space dimensions. The time and nodal propagation of the errors are depicted graphically. Also included in the computer software is a subroutine for plotting the isotherms in various geometries.     

NEW IMPLEMENTATION OF THE LP ALGORTHM FOR OPTIMAL REAL POWER RESCHEDULING

ABSTRACT

A new implementation of an LP algorithm for security-constrained preventive rescheduling of real power is described. Rescheduling of generation and load (if required) is used to maintain a secure condition by avoiding line overloads. A dual linear programming formulation of the optimal rescheduling is developed. The weighted minimum deviations in real power generations and loads are chosen as the objective function in the LP formulation. Inclusion of inequality constraints on active line flow limits and equality constraint on real power generation-load balance assures a solution representing a secure system. Transmission losses are also taken into account in the constraint function. Change in customer demands can be brought into the objective function. The line losses are also brought into the optimization in the form of an equality constraint. The algorithm has options to choose selected generators or loads to take part in the optimization. The proposed method is tested on four representative power systems. These tests show very encouraging results.     

Reexamination of the Kaolinite-to-Mullite Reaction Series

The kaolinite-to-mullite reaction series was reexamined with special attention to the nature of the metaphase, the eontroversial spinel phase, and the cause of the exothermic peak at 980°C. Amorphous SiO₂ forms during the exothermic reaction; it can be leached by alkali extraction. When the residual cubic phase is heated further, it forms mullite only. This result indicates that the cubic phase is an Al-Si spinel and that metakaolinite is an AI₂O₃-SiO₂ compound. It was established that the exotherm exhibited by kaolinite at 980°C represents the sudden transformation of metakaolinite to Al-Si spinel, the crystallization of mullite, and the liberation of amorphous SiO₂. The AI-Si spinel has the same composition as mullite, containing both AI(IV) and AI(VI). This spinel transforms into mullite at the second exothermic peak; no amorphous SiO₂ is liberated.     

Modeling and analysis of singular systems via orthogonal triangular functions

This paper presents a new approach to singular system analysis by modeling the system in terms of orthogonal triangular functions (TFs). The proposed method is more accurate compared to block pulse function-based analysis with respect to mean integral square error (MISE). A numerical example involving four states of a singular system is treated and solutions obtained thereof. Four tables and relevant curves are presented to compare the respective coefficients in block pulse function (BPF) domain as well as in TF domain. The percentage error of the samples determined via TF domain are compared with the exact samples of the states. Furthermore, MISE for both BPF and TF analysis are computed and compared to reveal the efficiency of TF-based analysis.     

A new recurslve method for the analysis of linear time invariant dynamic systems via double-term triangular functions （DTTF） in state space environment

This paper presents a new recursive method for system analysis via double-term triangular functions (DTTF) in state space environment. The proposed method uses orthogonal triangular function sets and proves to be more accurate as compared to single term Walsh series (STWS) method with respect to mean integral square error (MISE). This has been established theoretically and comparison of error with respect to MISE is presented for clarity. A numerical example is treated to establish the proposed method. Relevant curves for the solutions of states of the dynamic system are also presented with plots of percentage error for DTTF-based analysis.     

A survey on sensor localization

Localization is one of the fundamental problems in wireless sensor networks (WSNs), since locations of the sensor nodes are critical to both network operations and most application level tasks. Although the GPS based localization schemes can be used to determine node locations within a few meters, the cost of GPS devices and non-availability of GPS signals in confined environments prevent their use in large scale sensor networks. There exists an extensive body of research that aims at obtaining locations as well as spatial relations of nodes in WSNs without requiring specialized hardware and/or employing only a limited number of anchors that are aware of their own locations. In this paper, we present a comprehensive survey on sensor localization in WSNs covering motivations, problem formulations, solution approaches and performance summary. Future research issues will also be discussed.