Low turn-on voltage and series resistance of polarization-induced InGaN-GaN LEDs by using p-InGaN/p-GaN superlattice

We have demonstrated high-performance InGaN-GaN multiple quantum-wells light-emitting diodes (LEDs) using polarization-induced (PI) p-InGaN-GaN superlattice. Electrical measurements show that PI LEDs produce much lower series resistance and turn-on voltage (at 20 mA) as compared to those of normal LEDs without the superlattice. It is also shown that the output power and photon wavelength of the PI LEDs remain electrically stable up to a high stress region of 200 mA. However, those of normal LEDs become electrically and optically degraded in excess of 120 mA. These results show that the use of the PI effect is very effective to the improvement of the electrical properties of LEDs.     

Leak behavior of SCC degraded steam generator tubings of nuclear power plant

A forced outage due to a steam generator tube leak in a Korean nuclear power plant has been reported [Kim, J.S., Hwang, S.S., et al., 1999. KAERI Internal Report (Korean). Destructive analysis on pulled tubes from Ulchin unit 1. Korea Atomic Energy Research Institute]. Primary water stress corrosion cracking has occurred in many tubes in the plant, and they were repaired using sleeves or plugs. In order to develop proper repair criteria, it is necessary to understand the leak behavior of the tubes containing stress corrosion cracks. Cracked specimens were prepared using a room temperature cracking technique, and the leak rates and burst pressures of the degraded tubes were determined both at room temperature and at a high temperature. Some tubes with 100% through wall cracks did not show a leakage at 10.8 MPa, which is the typical pressure difference of the pressurized water reactors (PWRs) during a normal operation. In some tests, the leak rates of the tubes increased with time at a constant pressure. In a high temperature pressure test at 282 °C one specimen showed a very small leakage at 18.6 MPa, which stopped after a small increase in the test pressure. Because stress corrosion cracks can develop at relatively low stresses, even 100% through wall cracks can be so tight that they will not leak at a normal operating pressure.     

Period And Priority Assignment Method For Dcs Design

Distributed control systems (DCS) used in industry environments consist of sensors, actuators, and controllers that are connected with a fieldbus. It is difficult to design the DCS while guaranteeing the time‐critical requirements because of both communication delays due to the fieldbus and computation delays due to many tasks executed in one node. This paper proposes a priority assignment method and a period assignment method that find the shortest periods of control loops and guarantee the end‐to‐end constraints such as precedence constraints and timing constraints. Also, a DCS design method is presented by using the proposed two assignment methods. The presented design method considers the worst‐case response times of tasks and messages simultaneously and is applicable to a practical DCS, which consists of several constraints. The design method is validated by examples.     

High‐performance thin‐film transistor using silicide‐mediated crystallization

Abstract— We studied the silicide‐mediated crystallization of a‐Si for low‐temperature polycrystalline‐silicon (LTPS) on glass. By controling the heating method and Ni density on the a‐Si, the grain size could be increased to 40 μm. Radial grain growth from a NiSi₂ crystalline nucleus gives rise to a large‐grain poly‐Si without amorphous phase inside. A field‐effect mobility of over 200 cm²/V‐sec was achieved by using LTPS.     

Characteristics of carbon fiber phenolic composite for journal bearing materials

Journal bearing materials are required to have special characteristics such as compatibility with rubbing interface materials, embeddability for particles and wear debris, conformability to accommodate misalignment, thermal and corrosion resistance. Although white metals or babbitt metals used in most journal bearing have almost the required characteristics, they have possibility of seizure between the bearing material and the journal when the oil film is broken.

In this study, a hybrid composite journal bearing composed of carbon fiber reinforced phenolic composite liner and metal backing was manufactured to solve the seizure problem of metallic journal bearing materials because the carbon fiber has self-lubricating ability and the phenolic resin has thermal resistance characteristics. To estimate the wear resistance of carbon fiber phenolic composite, wear tests were performed at several pressures and velocities. The oil absorption characteristics, coefficient of thermal expansion, strength and stiffness of the composite were also tested. Using the measured stiffness values, the thermal residual stresses in the composite were calculated to check the reliability of the composite journal bearing.     

Analysis of Plasma Reaction for Decomposition of CHF3 in a Dielectric Barrier Discharge

The decomposition of CHF₃ in a mixture with O₂ and Ar was investigated in a coaxial dielectric barrier discharge at atmospheric pressure. CHF₃ decomposition increased linearly in regard to specific energy input (SEI), whereas energy efficiency decreased. The main product was CO_2, and its selectivity increased with high SEI and the presence of O₂ in the feed, but an increase of O₂ in the feed led to a decrease in decomposition rate. An increase in total flow rate led to an increase of the absolute amount of CHF₃ decomposition and energy efficiency; however, the decomposition of CHF₃ decreased. A complete CHF₃ decomposition occurred under an SEI of 1.54 kJ/L with the selectivity of CO₂ and CO as 89.87% and 7.00%, respectively. Optical emission spectroscopic analysis could explain the available reaction pathways for CHF₃ decomposition in the CHF₃/O₂/Ar atmospheric plasma and show the possibility of F₂ and HF formation.     

SAHPPA: a novel power pinch analysis approach for the design of off-grid hybrid energy systems

This work proposes a novel approach called stand-alone hybrid system power pinch analysis (SAHPPA), which is particularly applicable for the design of off-grid distributed energy generation systems. The enhanced graphical tool employs new ways of utilising the recently introduced demand composite curve and supply composite curve while honouring and adapting fundamental energy systems engineering concepts. The SAHPPA method is capable of optimising the capacity of both the power generators and energy storage for biomass (i.e. non-intermittent) and solar photovoltaic (i.e. intermittent) energy technologies, which is a contribution to the emerging area of power pinch analysis. In addition, the procedure considers all possible efficiency losses in the overall system encompassing the charging–discharging and current inversion processes.     

CHIR99021 Augmented the Function of Late Endothelial Progenitor Cells by Preventing Replicative Senescence

Endothelial progenitor cells (EPCs) are specialized cells in circulating blood, well known for their ability to form new vascular structures. Aging and various ailments such as diabetes, atherosclerosis and cardiovascular disease make EPCs vulnerable to decreasing in number, which affects their migration, proliferation and angiogenesis. Myocardial ischemia is also linked to a reduced number of EPCs and their endothelial functional role, which hinders proper blood circulation to the myocardium. The current study shows that an aminopyrimidine derivative compound (CHIR99021) induces the inhibition of GSK-3β in cultured late EPCs. GSK-3β inhibition subsequently inhibits mTOR by blocking the phosphorylation of TSC2 and lysosomal localization of mTOR. Furthermore, suppression of GSK-3β activity considerably increased lysosomal activation and autophagy. The activation of lysosomes and autophagy by GSK-3β inhibition not only prevented replicative senescence of the late EPCs but also directed their migration, proliferation and angiogenesis. To conclude, our results demonstrate that lysosome activation and autophagy play a crucial role in blocking the replicative senescence of EPCs and in increasing their endothelial function. Thus, the findings provide an insight towards the treatment of ischemia-associated cardiovascular diseases based on the role of late EPCs.