Search

The released NOx during fuel combustion is one of the major air pollutants, directly related to acid rain and photochemical smog. At present, there is not an economical and effective method of inhibiting NOx emission from sintering flue gas. Therefore, controlling the conditions of fuel combustion is extremely required for the reduction in NOx. The current research investigated the effects of different combustion parameters on the formation of NOx for three type of coals. The formation of NOx decreased with increasing temperature and heating rate while it increased when oxygen content in an atmosphere increased. Anthracite coal replacement with coke up to 100 pct promoted a decrease in the formed NOx amount and XNO by 21 and 53 pct, respectively. The addition of CaO and FeO enhanced the conversion of nitrogen to NOx, especially at temperatures below 1273 K (1000 °C). Taking both the oxidation reaction to form NOx and reduction reaction of NOx to form N2 into account, the activation energy (EA) values of anthracite and coke were evaluated to be 2.2 and 3.6 kJ/mol, respectively. The combustion of semi-anthracite coal emitted the largest amount of NOx, but the anthracite coal containing less fuel-N than other coals showed the highest value of XNO, which indicates that nitrogen content in coal is not the major factor affecting the formation of NOx. The change in nitrogen functionality after combustion process might be the reason for the unpredicted results in the XNO. The pyrrolic-N in anthracite coal might be considered to be the major functional form that directly affects the conversion of nitrogen to NO.

This paper reports smart wireless sensor node for Structural Health Monitoring (SHM) that is capable of operation with energy harvesting systems using piezoelectric materials. A large amount of research has focused on utilizing the impedance method for structural health monitoring but these studies required expensive and bulky impedance analyzers, which are unsuitable for field deployment. Piezoelectric materials can be used as mechanisms to transfer ambient vibrations into electrical energy that can be stored and used to power other devices. In this study, three types of piezoelectric materials were evaluated experimentally for use as power harvesting devices. In general, the power produced by the vibrations of piezoelectric devices is low, meaning that the equipment powered by the device cannot be operated effectively. Therefore, a time delay circuit and reset IC chip was used to improve the efficiency of the electrical power generated. The experimental results were used to estimate the efficiency of these devices and identified the feasibility of their use in practical applications.

We investigate how the second-order learning process moderates the relationship between innovation performance and two types of knowledge seeking behavior, namely exploration and exploitation. We reinvestigate the second-order learning process of the top 100 Korean firms from 1997 to 2007 by capturing CEO turnover, board turnover, and R&D alliances. We argue that the current findings about exploration and exploitation should be reclassified in terms of innovation input and output. We suggest that researchers investigate the organizational learning process to understand the link between innovation inputs and outputs. Our empirical results show that while innovation inputs are not related to exploratory outputs, the second-order learning process reshapes the relationship between both exploration/exploitation type innovation inputs and exploratory innovation outputs, and that the new focus of organizational learning process can refine current innovation literature.

Resistive random-access memory (ReRAM) devices based on halide perovskites have recently emerged as a new class of data storage devices, where the switching materials used in these devices have attracted extensive attention in recent years. Thus far, three-dimensional (3D) halide perovskites have been the most investigated materials for resistive switching memory devices. However, 3D-based memory devices display ON/OFF ratios comparable to those of oxide or chalcogenide ReRAM devices. In addition, perovskite materials are susceptible to exposure to air. Herein, we compare the resistive switching characteristics of ReRAM devices based on a quasi-two-dimensional (2D) halide perovskite, (PEA)2Cs3Pb4I13, to those based on 3D CsPbI3. Astonishingly, the ON/OFF ratio of the (PEA)2Cs3Pb4I13-based memory devices (109) is three orders of magnitude higher than that of the CsPbI3 device, which is attributed to a decrease in the high-resistance state (HRS) current of the former. This device also retained a high ON/OFF current ratio for 2 weeks under ambient conditions, whereas the CsPbI3 device degraded rapidly and showed unreliable memory properties after 5 days. These results strongly suggest that quasi-2D halide perovskites have potential in resistive switching memory based on their desirable ON/OFF ratio and long-term stability. A type of computer memory that stores data by changing the resistance of insulating crystals can be made more durable with organic chemical additives. Resistive memory devices constructed from inorganic crystals known as halide perovskites are inexpensive and have minimal power requirements. However, they can degrade quickly in humid conditions. Hyojung Kim from Seoul National University in South Korea and colleagues now report that these stability issues can be improved by sandwiching thin layers of aromatic hydrocarbons between halide perovskite crystals. The water-repelling nature of the organic molecules helps double the lifespan of the new hybrid compared to an unmodified halide perovskite device. In addition, the organic layers augment the differences between ‘ON’ and ‘OFF’ resistive memory states, making device operation more reliable. ReRAM devices based on halide perovskites have recently emerged as a new class of data storage device, where the switching materials used in these devices have attracted huge attention in recent years. In this study, we compare the resistive switching characteristics of ReRAM devices based on a quasi-2D halide perovskite, (PEA)2Cs3Pb4I13, to those based on 3D CsPbI3. Astonishingly, the ON/OFF ratio of the (PEA)2Cs3Pb4I13-based memory devices was much higher than that of the CsPbI3 device. Also this device retained a high ON/OFF current ratio for two weeks under ambient conditions, whereas the CsPbI3 device degraded rapidly and showed unreliable memory properties after five days. We strongly believe that quasi-2D halide perovskites have potential in resistive switching memory based on their high ON/OFF ratio and long-term stability.