Sebelas Maret University

About: Sebelas Maret University is a education organization based out in Surakarta, Indonesia. It is known for research contribution in the topics: Population & Public health. The organization has 10901 authors who have published 10832 publications receiving 33057 citations. The organization is also known as: Universitas Negeri Surakarta & Universitas Sebelas Maret.

A Note on Multiple Secret Sharing Using Chinese Remainder Theorem and Exclusive-OR

Abstract: This paper reviews the former existing scheme on (n,n) -multiple secret sharing (MSS) for color images along with its slight limitation. This scheme generates a set of n shared images from a set of n secret images using the Chinese remainder theorem (CRT) and Boolean exclusive-OR (XOR) operation. This scheme works well if the number of secret images n is even number. However, the former scheme has a slight problem while the number of secret images n is an odd number. This paper proposes a new technique to overcome this problem by introducing symmetric and transferred masking coefficients to generate a set of shared images. To further improve the security level of the proposed method, a set of secret images is first transformed with hyperchaotic scrambling method before generating shared images. The security of the proposed (n,n)-MSS can also be increased by merging a shared color image into 2-D matrix representation. As documented in the experimental results, the proposed method offers a promising result on (n,n) -MSS scheme regardless of the number of secret images n is odd or even number. In addition, the proposed method outperforms the former existing (n,n)-MSS schemes in terms of quantitative measurements.

Synthesis of Monophasic CaxBa(1−x)TiO3 Nanoparticles with High Ca Content (x > 23%) and Their Photoluminescence Properties

Abstract: We report for the first time the fabrication of monophasic CaxBa(1−x)TiO3 nanoparticles with high Ca content using a flame assisted spray pyrolysis (FASP) method. The biphasic structure (mixture of tetragonal BaTiO3 and orthorhombic CaTiO3 phases) was not detected in nanoparticles where x > 23%. The as-prepared nanoparticles were spherical, nonagglomerated, and polycrystalline with a relatively narrow size distribution (σg= 1.23 − 1.28). STEM-EDS mapping revealed that all components (Ca, Ba, Ti) were homogeneously distributed inside the nanoparticles. The optical properties were evaluated by doping of CaxBa(1−x)TiO3 nanoparticles with Pr3+ ions. CaxBa(1−x)TiO3:Pr3+ nanophosphors exhibited an intense red emission at a wavelength of 612 nm. Interestingly, the excitation-wavelength peaks varied over the range of 323.2 to 354.2 nm by variation of x.

Study on coal gasification with soot formation in two-stage entrained-flow gasifier

Abstract: Concerning the global warming due to large CO2 emission, the efficient use of coal becomes important for getting sustainable energy production. Coal gasification under CO2-rich condition is expected to be an effective way to produce a concentrated and pressurized carbon dioxide stream, resulting in reduction in separation energy of CO2 for CCS. Moreover, the soot formation, which is of significant environmental concern, is still being neglected in the past studies of coal gasification. A one-step soot formation reaction mechanism is proposed in this study and implemented in numerical simulations of coal gasification with the aim of describing the gasification behaviors in a two-stage entrained-flow gasifier. In addition, the effects of O2 ratio and CO2 concentration on soot concentration, syngas heating value and carbon conversion are numerically studied in an effort to increase the syngas production. The Eulerian–Lagrangian approach is applied to solve the Navier–Stokes equation and the particle dynamics. Finite rate/eddy dissipation model is used to calculate the rate of nine homogeneous gas-to-gas phase reactions including soot formation and soot oxidation. While only finite rate is used for the heterogeneous solid-to-gas phase reactions. It is found that formation of soot enhances the H2 production in the gasifier. Carbon conversion gradually increases with an increase in O2 ratio, while producing a low heating value syngas beyond a certain limit of O2 ratio. In contrast, an increase in CO2 concentration in the gasifier increases heating value of product syngas.

Cooperative inventory model for vendor-buyer system with unequal-sized shipment, defective items and carbon emission cost

Abstract: We develop an integrated inventory model for single-vendor single-buyer with deterministic demand. The vendor’s production process may be deteriorated during production run and results to some defective items. The defective probability is assumed to be uniformly distributed. The shipment from vendor to buyer is made in unequal size over multiple shipments. We also incorporate the carbon emission cost and investigate the environmental impact on the model. The results of the study show that adopting unequal-sized shipment policy in the model which considering defective items will result in lower carbon emission cost and total cost compared to an equal-sized policy. Furthermore, the increase in defective probability will lead to the increase of carbon emission cost.