Dynamic sectorization of microcells for balanced traffic in CDMA:genetic algorithms approach

With the increase of cellular users, traffic hot spots and unbalanced call distributions are common in wireless networks. As a solution to this problem, code-division multiple-access techniques enable a base transceiver station to connect microcells with optical fibers and to control the channels by sectorizing the microcells. To solve the load balancing among microcells, we dynamically sectorize the microcells depending on the time-varying traffic. The microcell sectorization problem is formulated as an integer linear programming that minimizes the blocked and handoff calls in the network. In the proposed sectorization, proper, connected, and compact sectors are considered to keep the handoffs as small as possible while satisfying the channel capacity at each sector. Three genetic algorithms (GAs) are proposed to solve the problem: standard GA, grouping GA, and parallel GA. Computational results show that the proposed GAs are highly effective. All three GAs illustrate outstanding performance for small size problems. The parallel GA, which is based on the operators used in grouping GA, demonstrates excellent solution quality in a reasonable time     

A Low-Noise Amplifier With Tunable Interference Rejection for 3.1- to 10.6-GHz UWB Systems

An ultrawideband common-gate low noise amplifier with tunable interference rejection is presented. The proposed LNA embeds a tunable active notch filter to eliminate interferer at 5-GHz WLAN and employs a common-gate input stage and dual-resonant loads for wideband implementation. This LNA has been fabricated in a 0.18-$mu$m CMOS process. The measured maximum power gain is 13.2 dB and noise figure is 4.5–6.2 dB with bandwidth of 3.1–10.6 GHz. The interferer rejection is 8.2 dB compared to the maximum gain and 7.6 dB noise figure at 5.2 GHz , respectively. The measured input P1dB is ${-} $11 dBm at 10.3 GHz. It consumes 12.8 mA from 1.8-V supply voltage.      

Exposure to ethyl carbamate in alcohol-drinking and nondrinking adults and its reduction by simple charcoal filtration

The risk of exposure to ethyl carbamate from the consumption of kimchi, soy sauce, and alcoholic beverages was assessed in alcohol-drinking and nondrinking adults. An alcohol-drinking adult obtains 5.6–9.2 ng/kg bw/day of ethyl carbamate through the addition of kimchi and soy sauce, while a nondrinking adult receives 3.3–4.0 ng/kg bw/day via kimchi and soy sauce alone. The average excess cancer risk of an alcohol-drinking adult (3.9 × 10^?7) was also twice higher than that of an adult who does not drink (1.9 × 10^?7). We achieved a maximum of 47% and 45% removal of the ethyl carbamate present in diluted spirits and soy sauce, respectively, through a simple charcoal filtration process. This resulted in a reduction of the average daily intakes of ethyl carbamate through diluted spirits and soy sauce from 1.7 and 2.2 ng/kg bw/day to 0.9 and 1.2 ng/kg bw/day, respectively.     

Wi‐Fi‐based modeling and hybrid routing scheme for delay‐tolerant public bus network

Delay‐ or Disruption‐Tolerant Networking (DTN) is a communications approach that is utilized in easily disrupted or delayed networks. Examples of such networks are often found in heterogeneous networks, mobile or extreme terrestrial networks, and planned networks in space. In this paper, we examine the metropolitan bus network as a research target of DTN for a public transport network. We analyze the metropolitan bus network through spatial and temporal modeling using an existing Bus Information System (BIS) database. On the basis of the results of our analysis, we propose and design an appropriate DTN routing scheme called Hybrid Position‐based DTN Routing. This scheme uses position‐based routing instead of address‐based routing by soliciting infrastructural help from nearby Access Points for the real‐time BIS location service. We simulated our scheme using a WLAN for the wideband DTN communication and evaluated it by comparing it with traditional Ad hoc flooding, Epidemic routing, and strategic protocol steps in our own algorithm. The results indicate that our scheme achieves reasonably high performance in terms of packet delivery ratio, latency, and resource usage. Copyright © 2013 John Wiley & Sons, Ltd.     

Design,Synthesis, and Versatile Processing of Indolo[3,2‐b]indole‐Based π‐Conjugated Molecules for High‐Performance Organic Field‐Effect Transistors

A series of indolo[3,2‐b]indole (IDID) derivatives comprising the core unit of N,N‐dihexyl‐IDID with different aromatic and aliphatic substituents at 2‐ and 7‐position are designed and synthesized to construct high‐performance organic semiconductors by different processing routes. Structure‐property relationship of the derivatives is comprehensively studied in terms of their photophysical, electrochemical, structural, and electrical characteristics. IDID derivatives are either evaporated in vacuum or dissolved in common organic solvents to ensure applicalbility in different processing routes toward outstanding p‐type semiconductor films. Among others, the excellently soluble compound 4H4TIDID (with 2‐ and 7‐substituents of 5‐hexyl‐2,2′‐bithiophene moiety, solubility >20 wt% in chloroform), shows the highest field‐effect hole mobility of 0.97 cm² V^?1 s^?1 in a device constructed by vacuum‐deposition and 0.18 cm² V^?1 s^?1 in device cosntructed by spin‐coating, respectively. The 2D grazing incidence X‐ray diffraction of 4H4TIDID films in both devices identically show the 2D molecular orientation favorable for the high transistor mobility.     

Utilization of the Antiferromagnetic IrMn Electrode in Spin Thermoelectric Devices and Their Beneficial Hybrid for Thermopiles

The thermoelectric effect in various magnetic systems, in which electric voltage is generated by a spin current, has attracted much interest owing to its potential applications in energy harvesting, but its power generation capability has to be improved further for actual applications. In this study, the first instance of the formation of a spin thermopile via a simplified and straightforward method which utilizes two distinct characteristics of antiferromagnetic IrMn is reported: the inverse spin Hall effect and the exchange bias. The former allows the IrMn efficiently to convert the thermally induced spin current into a measurable voltage, and the latter can be used to control the spin direction of adjacent ferromagnetic materials. It is observed that a thermoelectric signal is successfully amplified in spin thermopiles with exchange‐biased IrMn/CoFeB structures, where an alternating magnetic alignment is formed using the IrMn thickness dependence of the exchange bias. The scalable signal on a number of thermopiles allowing a large‐area application paves the way toward the development of practical spin thermoelectric devices. A detailed model analysis is also provided for a quantitative understanding of the thermoelectric voltages, which consist of the spin Seebeck and anomalous Nernst contributions.     

Urchin‐Like CoSe2 as a High‐Performance Anode Material for Sodium‐Ion Batteries

Urchin‐like CoSe₂ assembled by nanorods has been synthesized via simple solvothermal route and has been first applied as an anode material for sodium‐ion batteries (SIBs) with ether‐based electrolytes. The CoSe₂ delivers excellent sodiation and desodiation properties when using 1 m NaCF₃SO₃ in diethyleneglycol dimethylether as an electrolyte and cycling between 0.5 and 3.0 V. A high discharge capacity of 0.410 Ah g^?1 is obtained at 1 A g^?1 after 1800 cycles, corresponding to a capacity retention of 98.6% calculated from the 30th cycle. Even at an ultrahigh rate of 50 A g^?1, the capacity still maintains 0.097 Ah g^?1. The reaction mechanism of the as‐prepared CoSe₂ is also investigated. The results demonstrate that at discharged 1.56 V, insertion reaction occurs, while two conversion reactions take place at the second and third plateaus around 0.98 and 0.65 V. During the charge process, Co first reacts with Na₂Se to form Na_xCoSe₂ and then turns back to CoSe₂. In addition to Na/CoSe₂ half cells, Na₃V₂(PO₄)₃/CoSe₂ full cell with excessive amount of Na₃V₂(PO₄)₃ has been studied. The full cell exhibits a reversible capacity of 0.380 Ah g^?1. This work definitely enriches the possibilities for anode materials for SIBs with high performance.     

Demonstration of Time‐ and Wavelength‐Division Multiplexed Passive Optical Network Based on VCSEL Array

We demonstrate a time‐ and wavelength‐division multiplexed passive optical network system employing a vertical‐cavity surface‐emitting laser array–based optical line terminal transceiver and a tunable bidirectional optical subassembly–based optical network terminal transceiver. A packet error–free operation is achieved after a 40 km single‐mode fiber bidirectional transmission. We also discuss an arrayed waveguide grating, a photo detector array based on complementary metal–oxide–semiconductor photonics technologies, and low‐cost key devices for deployment in access networks.     

Operation of single transistor type ferroelectric random access memory

Verification was sought for the memory operation of a single transistor type ferroelectric random access memory (1T type FeRAM) with a circuit model for a memory cell transistor combined with a precharged capacitive decoupling sensing scheme. The wiring scheme of the 1T type FeRAM array was also proposed based on the operation of the fabricated memory cell transistor. As a result, the memory operation of 1T type FeRAM was confirmed at a low current level with high sensing speed and no reference cell, and the design and verification of the full chip were achieved.     

Mechanical and electrical properties of electrospun CNT/PVDF nanofiber for micro-actuator applications

Electrospun polyvinylidene fluoride (PVDF)-containing carbon nanotubes (CNT) were prepared for use in fabricating actuator materials. Actuating displacement was measured in an electrochemical environment. The electrospun nanofibers were arranged using a drum-type collector, and morphology was investigated using a field emission-scanning electron microscope. The uniformity of dispersion of CNT in the PVDF nanofibers was monitored by electron probe X-ray micro-analysis. Tensile strength and electrical resistivity results were used as an indication of the state of alignment. The electrospun CNT/PVDF nanofiber sheets exhibited better mechanical and electrical properties in the arranged direction. The efficiency and electrical capacities of electrospun CNT/PVDF nanofiber sheet were compared with those of cast PVDF sheets for use in actuator applications in electrochemical environments. The electrospun CNT/PVDF nanofiber sheets exhibited much better actuator performance than PVDF sheets, which are attributed to their superior electrical properties.

Highlights

(1) The interfacial durability of CNT/PVDF nanofibers was enhanced to increase contact area by reinforcing CNT.

(2) The efficiency of CNT/PVDF actuators was improved due to interfacial properties.

(3) Thin thickness drum-type collector was made to enhance nanofiber alignment.

(4) The arranged CNT/PVDF nanofibers exhibited better mechanical and actuating displacements.