MIMO receivers considering preamble collisions for grant-free random access in machine type communication systems

Telecommunication Systems - One of the main requirements for next generation mobile or wireless communication systems is to effectively support a large number of machine type communication (MTC)...     

Optimal thermo-economic design of a PAFC-ORC combined power system

Journal of Mechanical Science and Technology - Phosphoric acid fuel cells (PAFCs) are appropriate for applications that require high-quality power because of their high reliability. We propose a...     

Preparation and luminescence properties of novel K2ZnP2O7: Mn2+ green phosphor

Novel green-emitting phosphors K₂Zn_1???xP₂O₇: x mol% Mn²⁺ have been successfully prepared using classical solid-state reaction method in air atmosphere, doped by different Mn²⁺ ion contents, namely x?=?0.5, 1, 1.25 and 1.5 mol%. The samples were characterized by the thermogravimetric (ATD/ATG/DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), steady and time-resolved photoluminescence techniques. It was found that all K₂Zn_1???xP₂O₇: x mol% Mn²⁺ samples crystallize in the tetragonal phase with P4₂/mnm space group. Upon 425 nm excitation, K₂ZnP₂O₇: Mn²⁺ exhibits an intense broad green asymmetric emission band peaking at 520 nm, owing to the ⁴T₁→⁶A₁(⁶ S) transition of Mn²⁺ ion in K₂ZnP₂O₇. In addition, it is suggested that Mn²⁺ ions occupy more than one symmetry site in the host K₂ZnP₂O₇. The optimal Mn²⁺ ion concentration in K₂ZnP₂O₇:Mn²⁺ phosphor is 1 mol % and with the lifetime 9.81 ms.

     

Adiponectin Controls Nutrient Availability in Hypothalamic Astrocytes

Adiponectin, an adipose tissue-derived hormone, plays integral roles in lipid and glucose metabolism in peripheral tissues, such as the skeletal muscle, adipose tissue, and liver. Moreover, it has also been shown to have an impact on metabolic processes in the central nervous system. Astrocytes comprise the most abundant cell type in the central nervous system and actively participate in metabolic processes between blood vessels and neurons. However, the ability of adiponectin to control nutrient metabolism in astrocytes has not yet been fully elucidated. In this study, we investigated the effects of adiponectin on multiple metabolic processes in hypothalamic astrocytes. Adiponectin enhanced glucose uptake, glycolytic processes and fatty acid oxidation in cultured primary hypothalamic astrocytes. In line with these findings, we also found that adiponectin treatment effectively enhanced synthesis and release of monocarboxylates. Overall, these data suggested that adiponectin triggers catabolic processes in astrocytes, thereby enhancing nutrient availability in the hypothalamus.     

Highly efficient blue- and white-organic light-emitting diode based on dual recombination zones with a charge control layer

Highly efficient blue phosphorescent organic light-emitting diodes are investigated using iridium(Ill) bis[(4,6-di-fluorophenyl)-pyridinato-N,C2']picolinate doped in N,N'-dicarbazolyl-3,5-benzene (mCP) with a charge control layer (CCL) as the dual recombination zone (DRZ) system. DRZ with CCL was used to form a broad recombination zone and exciton confinement within each emission zone. Holes and electrons can be easily transported through the CCL, which were a mixed p-type mCP and n-type 2,2',2"-(1,3,5-benzenetryl) tris(1-phenyl)-1H-benzimidazol, for controlling the carrier movement. The CCL can play a role in triplet exciton blocking as expected from high triplet energy levels as well. Additionally, a white organic light-emitting diode was fabricated using a new phosphorescent orange emitter: bis[2-(2,4-difluorophenyl)pyridinato]iridium 2-(2-hydroxyphenyl)benzothia zolate doped in DRZ. The white device showed a maximum luminous efficiency of 23.15 cd/A, a maximum external quantum efficiency of 9.56%, and a maximum power efficiency of 13.37 lm/W. It also showed white emission with CIEx,y coordinates of (x = 0.33, y = 0.41) at 8 V.     

Design and analysis of asynchronous wakeup for wireless sensor networks

In wireless sensor networks, scheduling the sleep duration of each node is one of the key elements for controlling critical performance metrics such as energy consumption and latency. Since the wakeup interval is a primary parameter for determining the sleeping schedule, how to tune the wakeup interval is crucial for the overall network performance. In this paper, we present an effective framework for tuning asynchronous wakeup intervals of IEEE 802.15.4 sensor networks from the energy consumption viewpoint. First, we derive an energy consumption model of each node as an explicit function of the wakeup interval, and empirically validate the derived model. Second, based on the proposed model, we formulate the problem of tuning the wakeup interval with the following two objectives: to minimize total energy consumption and to maximize network lifetime. We show that these two problems can be optimally solved by an iterative algorithm with global information by virtue of the convexity of the problem structure. Finally, as practical solutions, we further propose heuristic optimization algorithms that only exploit local information. In order to develop heuristic algorithms, we propose two broadcasting schemes, which are entitled as maximum wakeup interval broadcasting and efficient local maximum broadcasting. These broadcasting algorithms enable nodes in the network to have heterogeneous wakeup intervals.     

Study on the electrical and optical properties of ITO and AZO thin film by oxygen gas flow rate

Transparent conductive oxide (TCO) thin films such as tin doped indium oxide (ITO), zinc doped indium oxide (IZO) and Al doped zinc oxide (AZO) have been widely used as transparent electrode for display. ITO and AZO thin films for display was prepared by the facing targets sputtering (FTS) system. The FTS method is called a plasma-free sputter method because the substrate is located apart from plasma. This system can deposit the thin film with low bombardment by high energetic particles in plasma such as γ-electrons, negative ions and reflected Ar atoms. ITO and AZO thin films were deposited on glass substrate at room temperature with oxygen gas flow rate and input power. And the electrical, structural and optical properties of the thin films were investigated. As a result, the resistivity of ITO, AZO thin film is 6?×?10^?4 Ω cm, 1?×?10^?3 Ω cm, respectively. And the optical transmittance of as-deposited thin films is over 80% at visible range.     

Measurement of a Customer Satisfaction Index for Improvement of Mobile RFID Services in Korea

One of the ubiquitous technology fields that have received the most attention recently from technology communities worldwide is mobile radio frequency identification (RFID). Mobile handsets loaded with RFID readers enable the identification and retrieval of information on RFID tagged objects. In Korea, a variety of mobile RFID services are currently being piloted, and their commercial roll‐out looks imminent. The goal of this study is to propose, ahead of the commercial launch of mobile RFID services, a customer satisfaction index (CSI) model for this service category and to then measure the CSI to derive practical implications for their providers and pointers related to the improvement of service. A web survey was conducted on Korean mobile phone subscribers who had participated in a mobile RFID pilot program. Using the results of this survey, we tested the CSI model and its hypotheses by employing a partial least‐squares‐based structural equation model analysis and calculated the index. We further conducted an importance‐performance analysis in order to provide insights that may be useful for improving the quality of mobile RFID services.