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Access Points (access + point)
Kinds of Access Points Selected AbstractsThe Nutrition, Aging, and Memory in Elders (NAME) study: design and methods for a study of micronutrients and cognitive function in a homebound elderly populationINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 6 2006Tammy M. Scott Abstract Background Micronutrient status can affect cognitive function in the elderly; however, there is much to learn about the precise effects. Understanding mediating factors by which micronutrient status affects cognitive function would contribute to elders' quality of life and their ability to remain in the home. Objectives The Nutrition, Aging, and Memory in Elders (NAME) Study is designed to advance the current level of knowledge by investigating potential mediating factors by which micronutrient status contributes to cognitive impairment and central nervous system abnormalities in the elderly. NAME targets homebound elders because they are understudied and particularly at risk for poor nutritional status. Methods Subjects are community-based elders aged 60 and older, recruited through area Aging Services Access Points. The NAME core data include demographics; neuropsychological testing and activities of daily living measures; food frequency, health and behavioral questionnaires; anthropometrics; gene status; plasma micronutrients, homocysteine, and other blood determinants. A neurological examination, psychiatric examination, and brain MRI and volumetric measurements are obtained from a sub-sample. Results Preliminary data from first 300 subjects are reported. These data show that the NAME protocol is feasible and that the enrolled subjects are racially diverse, at-risk, and had similar basic demographics to the population from which they were drawn. Conclusion The goal of the NAME study is to evaluate novel relationships between nutritional factors and cognitive impairment. These data may provide important information on potential new therapeutic strategies and supplementation standards for the elderly to maintain cognitive function and potentially reduce the public health costs of dementia. Copyright © 2006 John Wiley & Sons, Ltd. [source] Characteristics of Medical Surge Capacity Demand for Sudden-impact DisastersACADEMIC EMERGENCY MEDICINE, Issue 11 2006Samuel J. Stratton MD Objectives To describe the characteristics of the demand for medical care during sudden-impact disasters, focusing on local U.S. communities and the initial phases of sudden-impact disasters. Methods Established databases and published reports were used as data sources. Data were obtained to describe the baseline capacity of the U.S. medical system. Information for the initial phases of a sudden-impact disaster was sought to allow for characterization of the length of time before a U.S. community can expect arrival of outside assistance, the expected types of medical surge demands, the expected time for the peak in medical-care demand, and the expected health system access points. Results The earliest that outside assistance arrived for a community subject to a sudden-impact disaster was 24 hours, with a range from 24 to 96 hours. After sudden-impact disasters, 84% to 90% of health care demand was for conditions that were managed on an ambulatory basis. Emergency departments (EDs) were the access point for care, with peak demand time occurring within 24 hours. The U.S. emergency care system was functioning at relatively full capacity on the basis of data collected for the study that showed that annually, 90% of EDs were boarding admitted inpatients, and 75% were diverting ambulances. Conclusions As part of planning for sudden-impact disasters, communities should be expected to sustain medical services for 24 hours, and up to 96, before arrival of external resources. For effective medical surge-capacity response during sudden-impact disasters, there should be a priority for emergency medical care with a focus on ambulatory injuries and illnesses. [source] Performance evaluation of CSMA/ID MAC protocol for IP over WDM ring networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 11 2008Jih-Hsin Ho Abstract In this paper, a packet pre-classification media access control protocol based on a carrier sense multiple access with idle detection (CSMA/ID) scheme is investigated for supporting IP packets over all-optical WDM ring networks. The purpose of the protocol is to increase throughput and to decrease the packet transmission delay of IP packets over optical networks in a metropolitan area network. This protocol avoids both packet collision and packet fragmentation. In order to improve the utilization of the network, the packets transmitted from a local area network are first pre-classified into various class queues of an access point (AP) according to their length. After checking the available space based on the wavelength received by the receivers of the AP, the packets in the queues are transmitted. An analytical model is developed to evaluate the performance of the protocol, with simulation results showing good network efficiency. The proposed network has short-term variations that introduce unfairness conditions. This problem could be overcome by assigning a quota on individual queues to allow all queues fair access. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the performance of recursive space,frequency codes and iterative decoding in wideband OFDM-MIMO systems: simulated and measured resultsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2004Paul N. Fletcher Abstract In this paper, we study the performance of a bandwidth efficient space,frequency turbo encoding scheme over wideband channels. Results are presented for simulated wideband MIMO channels consisting of two transmit antennas and up to two receive antennas. In addition, wideband channel measurements undertaken with practical multi-element antenna structures at both the access point (AP) and mobile terminal (MT) are presented. Analysis is in terms of channel capacity, 10% channel outage capacity and space,frequency iterative decoding for an lEEE802.11a physical layer complaint modem. It is shown when operating with a spectral efficiency of 1.2 bits/s/Hz, the iterative decoded space,time codes comes within approximately 4.7 dB of 10% outage capacity over Rayleigh fading wideband channels with two transmit and two receive antennas. Over measured channels the iterative decoding scheme performs within 7.7 dB 10% of outage capacity. Losses due to channel state information estimation are also investigated. Copyright © 2004 John Wiley & Sons, Ltd. [source] Urban mesh and ad hoc mesh networksINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 2 2008Anders Nilsson Plymoth Mesh networking is currently gaining much attention, within both academia and industry. Mesh networking allows cheap and fast deployment of wireless services. It is regarded as a very promising solution for urban deployment scenarios as well as for temporary emergency response situations. Another related promising field is that of ad hoc wireless networking, which consists of mobile nodes that dynamically create and maintain a network without the need for any infrastructure. We propose a solution and architecture for urban mesh ad hoc networks, a network that combines mesh networking with ad hoc networks for urban environments. We present four types of ad hoc mesh and ad hoc mesh networks. The most general one consists of mesh nodes, called mesh points (MP), that act as a type of access point for user nodes (UN). The MPs have at least two interfaces: one which is used to communicate with UNs, and one which is used to maintain the mesh access network and transport data. These two interfaces can basically use any type of technology (IEEE 802.11 a/b/g, WiMax, etc.), and for capacity reasons it is generally regarded that the best solution is to let the mesh interface operate on a separate high-capacity channel or channels. An intricate part of these types of networks are routing and location services. In our solution, UN devices operate in ad hoc mode running an ad hoc routing protocol. This allows UNs that wish to communicate to connect directly in an ad hoc manner, or through an MP. An important question is therefore whether two UNs that wish to communicate should connect through the mesh or connect directly. We show that from a capacity point of view whether a UN should route its packets to the closest available MP, or through a ad hoc network, depends on the environment the network is located, the amount traffic and the type of protocols used. Since MPs need to know where to route packets within the mesh, i.e., locating the MP closest to the destination UN, each UN run a small application that registers the UN to the mesh network. In addition to the above features we have developed a new MAC that quickly queries two candidate nodes, which picks the candidate with the currently best radio conditions. This enable nodes to cope with deep dips in signal strength due to fast fading, a well-known problem in urban environments. We show that this new protocol achieves significantly lower delays. We also show that in dense urban environments performance and battery lifetime can be improved if ad hoc technologies are used. Copyright © 2007 John Wiley & Sons, Ltd. [source] Compact high-gain printed loop-antenna array integrated into a 5-GHz WLAN access pointMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010Tzi-Chieh Hong Abstract A printed, planar loop-antenna array having a compact structure and high-gain, directional radiation properties for WLAN operation in the 5 GHz band is presented. The antenna-array design is composed of four-folded loops arranged to be of 2 × 2 configuration, printed on both sides of a 1.6-mm thick FR4 substrate, and one system printed circuit board (PCB) serving as an efficient reflector for the loops. The antenna array is set within the boundary of the PCB (size of 50 mm ×65 mm) and stacked there above by a separation distance of 5.4 mm only. That's, the design integrates the system PCB of an access point (AP) into an internal antenna solution for compact outdoor AP applications. The results show that good input matching with voltage standing wave ratio (VSWR) below 1.5 over the 5150,5825 MHz band can be achieved. Directional radiation patterns with peak gain at about 10 dBi were also obtained. Details of the antenna design are described and discussed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2261,2267, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25487 [source] Visible light communication systems for optical video transmissionMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010J. Rufo Abstract This article describes an optical wireless system based on visible light communication (VLC), which allows a video broadcasting to reach a bit rate of 1 Mbps, although this system can also be used for low-speed sensor interconnections. The main advantages of this technology are the robustness against EM interference, safety for human eye, and security against undesired network access. In this article, we present the electronic structure of a low-cost VLC transceiver, the modulation process and the Ethernet interface that has been implemented in each AP (access point). Finally, some conclusions are drawn. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1572,1576, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25236 [source] Hybrid of monopole and dipole antennas for concurrent 2.4- and 5-GHz WLAN access pointMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009Jui-Hung Chou Abstract A novel hybrid of a 2.4-GHz monopole antenna and a 5-GHz dipole antenna is presented to provide concurrent 2.4 and 5 GHz band operation for access-point applications. The two antennas are arranged in a collinear structure and printed on a compact dielectric substrate with dimensions 12 mm × 60 mm. The monopole antenna has a meandered radiating strip and is short-circuited to a small ground plane through a shorting strip. The dipole antenna includes two sub-dipoles at the opposite side of a narrow ground plane and fed by a simple T-junction microstrip-line network. The two antennas are closely set with a distance of 1 mm only, yet good port isolation (S21) well below ,20 dB can be obtained. With a low profile, the proposed design can easily fit into the casing of some standard access points and allow the 2.4 and 5 GHz band signals to be simultaneously received or transmitted with no external diplexer required. Good omnidirectional radiation has been observed too. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1206,1209, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24281 [source] Characteristics of Medical Surge Capacity Demand for Sudden-impact DisastersACADEMIC EMERGENCY MEDICINE, Issue 11 2006Samuel J. Stratton MD Objectives To describe the characteristics of the demand for medical care during sudden-impact disasters, focusing on local U.S. communities and the initial phases of sudden-impact disasters. Methods Established databases and published reports were used as data sources. Data were obtained to describe the baseline capacity of the U.S. medical system. Information for the initial phases of a sudden-impact disaster was sought to allow for characterization of the length of time before a U.S. community can expect arrival of outside assistance, the expected types of medical surge demands, the expected time for the peak in medical-care demand, and the expected health system access points. Results The earliest that outside assistance arrived for a community subject to a sudden-impact disaster was 24 hours, with a range from 24 to 96 hours. After sudden-impact disasters, 84% to 90% of health care demand was for conditions that were managed on an ambulatory basis. Emergency departments (EDs) were the access point for care, with peak demand time occurring within 24 hours. The U.S. emergency care system was functioning at relatively full capacity on the basis of data collected for the study that showed that annually, 90% of EDs were boarding admitted inpatients, and 75% were diverting ambulances. Conclusions As part of planning for sudden-impact disasters, communities should be expected to sustain medical services for 24 hours, and up to 96, before arrival of external resources. For effective medical surge-capacity response during sudden-impact disasters, there should be a priority for emergency medical care with a focus on ambulatory injuries and illnesses. [source] Topographic spatial characterisation of grey seal Halichoerus grypus breeding habitat at a sub-seal size spatial grainECOGRAPHY, Issue 3 2001S. D. Twiss Expansion within breeding colonies may critically depend upon the availability of suitable breeding habitat. Here we use topographic modelling in a GIS to characterise suitable pupping habitat and accurately predict the pattern of colonisation in an expanding grey seal breeding colony-the Isle of May (Scotland), We use high resolution images from large format aerial photographs of the colony to generate sub-metre accurate Digital Terrain Models (DTMs), GIS modelling with these DTMs provides topographic measures of elevation, slope and ease of access to sea and freshwater pools at a 2 m grid cell size. Seal locations during the 1994 breeding season, with sex-age class, were also digitised from the same images. We examine how the physical attributes of cells (locations) with and without pups differ and identify areas suitable for pupping but remaining unoccupied during 1994. We predict patterns of future colonisation by characterising areas differentiated by the densities of pups within 5 m grid cells and identifying areas, both occupied or unoccupied, with a potential for increased future pupping densities. Our predictions were tested by examining pup distributions observed in the 1998 breeding season. Occupied sites were significantly closer to freshwater pools and access to the sea (p < 0.001) than unoccupied sites suggesting that proximity to water may restrict colony expansion before all areas of suitably flat terrain are occupied. All pup density classes occurred in sites with similar slope values and distance to pools. However, higher pupping densities occurred closer to access points (p = 0.014). Pup densities observed in 1998 revealed that our 1994 predictions were accurate (p < 0.0001). Only 12% of 466 grid cells had higher densities in 1998 than predicted, of which 88% differed by only 1 pup. These incorrectly classified cells occurred at the expanding edge of the colony (in a more topographically homogenous area) and at the main access points from the sea (major traffic zones). These results demonstrate the value of the accurate quantification of topographic parameters at the appropriate spatial grain (in this case below the size of the individual) for use in habitat classification and predictions of habitat utilization. [source] Lateral movement of common carp (Cyprinus carpio L.) in a large lowland river and floodplainECOLOGY OF FRESHWATER FISH, Issue 1 2009M. J. Jones Abstract,,, Common carp (Cyprinus carpio L.) are a major freshwater invader and knowledge of their movements is important for planning control efforts. To investigate the movement patterns of common carp, radio-tags were implanted into 46 adult fish; 37 near a large floodplain wetland, the Barmah-Millewa forest, and 9 in the Murray River approximately 175 km upstream. Tagged fish were located every second week between August 1999 and March 2001. Common carp occupied total linear ranges (TLR) between 0.4 and 238 km (mean 30 ± 61 km), with 25 fish (62.5%) occupying a TLR < 10 km. Two fish made large distance movements approximately 650 km downstream. Fish sex, the number of locations, time at large, or tagging location explained little variability (P > 0.05) in TLR. Monthly distance from release varied from 0.04 to 238 km (mean 15 ± 44 km), and was not significantly related to river discharge and water temperature, but 29 of 31 (93.5%) fish tagged at Barmah moved from the Murray River into adjacent floodplain habitats upon flooding. Five fish (12.5%) moved large distances (>127 km) upstream of the Barmah-Millewa forest. Fourteen fish (35%) showed site fidelity to within 20 m and usually occupied one or two home sites. Twenty-six fish (65%) showed site fidelity to within 100 m occupying up to five sites during the study period. Movement patterns of common carp were complex, and individuals exhibited different strategies, which is typical of invasive species. Efforts to control and potentially reduce common carp populations in regulated river-floodplain environments should target key floodplain access points and over-wintering habitats to reduce adult biomass, spawning and recruitment levels. [source] A modular access gateway for managing intermittent connectivity in vehicular communicationsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 2 2006Jörg Ott The Drive-thru Internet architecture allows exploiting intermittent connectivity by temporarily connecting to IEEE 802.11 WLAN access points at the roadside from moving vehicles. This poses numerous challenges to a mobile user's equipment: extreme networking characteristics such as short periods of connectivity, unpredictable disconnection times, and vastly varying transmission characteristics. Heterogeneous WLAN hotspot installations may also require different authentication mechanisms and credentials. We have designed a mobile access gateway to deal with these issues on behalf of a user (group) in a moving vehicle and provide usable connectivity for applications without requiring manual operation. The gateway maximises the use of short connectivity periods by detecting network access providing signalling functions for local application processes. It also allows using dedicated radio equipment to prolong connectivity periods. Finally, in selected multi-user scenarios, further performance improvements are conceivable by sharing (non-confidential) information across users and applications. Copyright © 2005 AEIT. [source] The level of Internet access and ICT training for health information professionals in sub-Saharan AfricaHEALTH INFORMATION & LIBRARIES JOURNAL, Issue 3 2008Grace Ada Ajuwon Background:,, Information and Communication Technologies (ICTs) are important tools for development. Despite its significant growth on a global scale, Internet access is limited in sub-Saharan Africa (SSA). Few studies have explored Internet access, use of electronic resources and ICT training among health information professionals in Africa. Objective:, The study assessed Internet access, use of electronic resources and ICT training among health information professionals in SSA. Methods:, A 26-item self-administered questionnaire in English and French was used for data collection. The questionnaire was completed by health information professionals from five Listservs and delegates at the 10th biannual Congress of the Association of Health Information and Libraries in Africa (AHILA). Results:, A total of 121 respondents participated in the study and, of those, 68% lived in their countries' capital. The majority (85.1%) had Internet access at work and 40.8% used cybercafes as alternative access points. Slightly less than two-thirds (61.2%) first learned to use ICT through self-teaching, whilst 70.2% had not received any formal training in the previous year. Eighty-eight per cent of respondents required further ICT training. Conclusions and recommendations:, In SSA, freely available digital information resources are underutilized by health information professionals. ICT training is recommended to optimize use of digital resources. To harness these resources, intergovernmental and non-governmental organizations must play a key role. [source] Secure fast WLAN handoff using time-bound delegated authenticationINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2009Hung-Yu Chien Abstract To support multimedia applications with good quality of services for roaming wireless local area network users, it is imperative to reduce the long re-authentication latency that users experience during handoff among access points (APs). Athough a great deal of research resources have been put into the reduction of the re-authentication latency, these schemes developed so far seem to either suffer from heavy overhead problems or have weak security. In this paper, we propose a novel approach to reducing the re-authentication latency. With the authentication server (AS) periodically delegating its authentication authority to the authenticated APs, the APs can authenticate the roaming users on behalf of the AS. As our performance analysis and simulation results demonstrate, our new approach is capable of greatly reducing the latency and overhead while achieving a high security level. Furthermore, it does not increase the complexity on the AP side because only the already existing four-way handshake with new keying mechanism is required. Copyright © 2008 John Wiley & Sons, Ltd. [source] A survey of current architectures for connecting wireless mobile ad hoc networks to the InternetINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2007Habib M. Ammari Abstract Connecting wired and wireless networks, and particularly mobile wireless ad hoc networks (MANETs) and the global Internet, is attractive in real-world scenarios due to its usefulness and praticality. Because of the various architectural mismatches between the Internet and MANETs with regard to their communication topology, routing protocols, and operation, it is necessary to introduce a hybrid interface capable of connecting to the Internet using Mobile IP protocol and to MANETs owing to an ad hoc routing protocol. Specifically, the approaches available in the literature have introduced updated versions of Mobile IP agents or access points at the edge of the Internet to help MANET nodes get multi-hop wireless Internet access. The main differences in the existing approaches concern the type of ad hoc routing protocol as well as the switching algorithm used by MANET nodes to change their current Mobile IP agents based on specific switching criteria. This paper surveys a variety of approaches to providing multi-hop wireless Internet access to MANET nodes. Copyright © 2006 John Wiley & Sons, Ltd. [source] WTCP: an efficient mechanism for improving wireless access to TCP servicesINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2003Karunaharan Ratnam Abstract The transmission control protocol (TCP) has been mainly designed assuming a relatively reliable wireline network. It is known to perform poorly in the presence of wireless links because of its basic assumption that any loss of a data segment is due to congestion and consequently it invokes congestion control measures. However, on wireless access links, a large number of segment losses will occur more often because of wireless link errors or host mobility. For this reason, many proposals have recently appeared to improve TCP performance in such environment. They usually rely on the wireless access points (base stations) to locally retransmit the data in order to hide wireless losses from TCP. In this paper, we present Wireless-TCP (WTCP), a new mechanism for improving wireless access to TCP services. We use extensive simulations to evaluate TCP performance in the presence of congestion and wireless losses when the base station employs WTCP, and the well-known Snoop proposal (A comparison of mechanisms for improving TCP performance in wireless networks. In ACM SIGCOMM Symposium on Communication, Architectures and Protocols, August 1996). Our results show that WTCP significantly improves the throughput of TCP connections due to its unique feature of hiding the time spent by the base station to locally recover from wireless link errors so that TCPs round trip time estimation at the source is not affected. This proved to be critical since otherwise the ability of the source to effectively detect congestion in the fixed wireline network is hindered. Copyright © 2003 John Wiley & Sons, Ltd. [source] Pinpointing users with location estimation techniques and Wi-Fi hotspot technologyINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2008Kevin Curran Location awareness is becoming an important capability for mobile computing; however, it has not been possible until now to provide cheap pervasive positioning systems. Wide area coverage is most famously achieved by using global positioning systems (GPS). A constellation of low-orbit satellites cover the earth's surface. Unfortunately GPS does not work indoors and has limited success in big cities because of the ,urban canyon' effect. PlaceLab is a research project that attempts to solve the ubiquity issues surrounding 802.11-based location estimation. PlaceLab, like RADAR, uses a device's 802.11 interface; however, it does not require the area to be pre-calibrated. It predicts location via the known positions of the access points detected by the device. Commonly used systems have a number of drawbacks, including cost, accuracy and the ability to work indoors. PlaceLab is a piece of open source software developed by Intel Research that can pinpoint a user within a Wi-Fi network. We set out here to investigate whether PlaceLab can be used as a means of establishing a user's position. This type of investigation could, if successful, pave the way for the development of other location-based applications. This report documents the efforts to answer the above question. PlaceLab was found to work, but only in ideal locations where factors such as the number of floors and the lack of available APs did not affect its use. It was concluded that these factors prevent the system from being effective as a means of establishing a user's position in most locations on campus. Copyright © 2008 John Wiley & Sons, Ltd. [source] Enabling location-based services in wireless LAN hotspotsINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 3 2005Yen-Cheng Chen The wide deployment of IEEE 802.11 Wireless LAN (WLAN) makes possible application services developed in WLAN hotspots. Owing to the small cell size in WLAN hotspots, it is practical to develop location-based services with the awareness of the WLAN access points (APs) that mobile devices currently access. In this paper, we propose an effective location determination technique using the inherent SNMP support in WLAN APs. It is shown that the current location of a mobile device can be determined from the SNMP traps sent by APs. Since the SNMP-based approach doesn't need any particular software or hardware in mobile devices, location-based services can be widely deployed, especially in public WLAN hotspots. To further enable location-based services through the WWW, this paper also considers the location determination of a mobile device from its IP address, retrieved in a WWW environment. In addition, we propose a web service framework for location-based services in WLAN hotspots. Thus, location-based services can be developed in a standard way.,Copyright © 2005 John Wiley & Sons, Ltd. [source] High-gain, short-circuited six-monopole-antenna system for concurrent, dual-band WLAN access pointsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2010Saou-Wen Su Abstract A high-gain, short-circuited multimonopole antenna system for wireless access points in the concurrent 2.4 and 5 GHz WLAN bands is presented. The antenna system mainly comprises a circular antenna ground and six short-circuited, single-band monopole antennas, among which the three antennas are designated for 2.4 and 5 GHz operation respectively. The monopole antennas are set in a sequential, rotating arrangement on the antenna ground, and the 2.4 and 5 GHz antennas are facing each other one by one. Experimental results show that well port isolation can be obtained between the antenna ports with high-gain properties over the 2.4 and 5 GHz bands. A design prototype is elaborated and discussed in the article. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2728,2732, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25588 [source] Hybrid of monopole and dipole antennas for concurrent 2.4- and 5-GHz WLAN access pointMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009Jui-Hung Chou Abstract A novel hybrid of a 2.4-GHz monopole antenna and a 5-GHz dipole antenna is presented to provide concurrent 2.4 and 5 GHz band operation for access-point applications. The two antennas are arranged in a collinear structure and printed on a compact dielectric substrate with dimensions 12 mm × 60 mm. The monopole antenna has a meandered radiating strip and is short-circuited to a small ground plane through a shorting strip. The dipole antenna includes two sub-dipoles at the opposite side of a narrow ground plane and fed by a simple T-junction microstrip-line network. The two antennas are closely set with a distance of 1 mm only, yet good port isolation (S21) well below ,20 dB can be obtained. With a low profile, the proposed design can easily fit into the casing of some standard access points and allow the 2.4 and 5 GHz band signals to be simultaneously received or transmitted with no external diplexer required. Good omnidirectional radiation has been observed too. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1206,1209, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24281 [source] Broadband coaxial antenna for WiMAX access-point applicationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2006Kin-Lu Wong Abstract A broadband coaxial antenna mainly comprising an upper square cylindrical plate and a lower square cylindrical ground is presented. The antenna functions like a two-wire dipole antenna, and furthermore provides a wide operating bandwidth of about 4 GHz (about 1.9 to 5.9 GHz in the study), making it very promising for application in Worldwide Interoperability for Microwave Access Forum (WiMAX) access points. The antenna has been successfully implemented, and experimental results are presented. The effects of the lower square cylindrical ground on the antenna performances are also analyzed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 641,644, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21432 [source] Improving health through youth sports: Is participation enough?NEW DIRECTIONS FOR YOUTH DEVELOPMENT, Issue 115 2007Michael F. Bergeron The health benefits of engaging in regular physical activity are widely known: enhanced cardiorespiratory fitness, increased muscular strength and endurance, and favorable cholesterol and other profiles. Nevertheless, particularly in youth sports programs run by volunteer, and perhaps inadequately trained, coaches, many youth may not realize the health benefits of sports participation due to a number of factors, among them, inappropriate coach-child ratios, limited space, or mismatched expectations between coaches and those of children and their parents. There are specific strategies that can be implemented to ensure that youth receive the maximize benefits from participation in sports. These strategies are presented in the following areas: frequency, intensity, and duration; cross-training or complementary exercise; access points; utilization of space and time; nutrition; and rest. For instance, with regard to the frequency of physical activity, some sports, including soccer, basketball, and singles tennis, require extensive physical effort over an extended period of time, while others, such as baseball and football, have a lot of downtime. Thus, in order for children and youth to meet the recommendation of participating in moderate or vigorous physical activity at least four times per week, sports programs need to have opportunities for all athletes to practice hard. Finally, the author discusses the point at which participation in sports might be too much, leading to significant injuries, frustration, and resentment. [source] Ethernet aggregation and core network models for effcient and reliable IPTV servicesBELL LABS TECHNICAL JOURNAL, Issue 1 2007Christian Hermsmeyer With the growing interest on wireline network architectures for residential triple-play and business Ethernet services there is a renewed demand for efficient and reliable packet-based transport capabilities between the content providers and the end users. Voice and data traffic carried over a variety of access technologies is collected via technology-specific access networks (e.g., digital subscriber line [xDSL], passive optical network [xPON], and wireless fidelity [WiFi]). Metro and core networks need to aggregate the various user flows from different access network nodes and provide scalable and cost-effective distribution of various flow types (e.g., Internet access, voice, video on demand, and broadcast TV services) to the relevant service access points. Varying quality of service and resiliency requirements for these services are being reflected in a new breed of converged Ethernet and optical network elements with capabilities to interwork the bearer-planes of these two networking technologies seamlessly. Network elements based on Ethernet/Optical converged technology are able to select the most fitting mechanisms from each networking technology to meet the transport requirements for each individual service demand better while providing significantly enhanced implementation and operational efficiencies. This paper discusses network architecture models and network elements addressing these goals. © 2007 Alcatel-Lucent. [source] Dry Season Den Use by Pygmy Spotted Skunk (Spilogale pygmaea) in a Tropical Deciduous Forest of MexicoBIOTROPICA, Issue 3 2009Lisette Cantú-Salazar ABSTRACT Dry season den use by the pygmy spotted skunk Spilogale pygmaea, an endemic and threatened species of western Mexico, was evaluated at the micro and macrohabitat level, in the tropical deciduous forest of Chamela, Jalisco, Mexico. During the dry seasons of 1997, 1998, and 2000, 79 skunk den sites (29 for females and 50 males) were located using Radiotelemetry. Dens were underground excavations with one to five access points, located mostly on open ground or under live or dead trees. Skunks exhibited a continued reuse of dens but evidence of simultaneous occupation by two or more skunks was not found. Microhabitat den-site analysis showed that skunks showed flexibility and individual variation in usage of the microhabitat surrounding den sites inside the forest. Macrohabitat den-site analysis showed that skunks were not selecting either tropical deciduous or tropical semideciduous forest; however, no dens were located outside the forest in transformed habitats, strengthening the hypothesis of the association of this species with the tropical deciduous forests on the Pacific coast of Mexico. The current deforestation rates of the tropical deciduous forest in the coast of Jalisco could be reducing the potential den sites for pygmy spotted skunks and exposing them to adverse environmental conditions and predation. RESUMEN El zorrillo pigmeo (Spilogale pygmaea) es una especie endémica del oeste de México y considerada en peligro de extinción. Estudiamos el uso de madrigueras por parte del zorrillo pigmeo a nivel de micro y macrohabitat durante la época seca en el bosque tropical deciduo de Chamela, Jalisco, México. Durante las época seca de 1997, 1998 y 2000 localizamos un total de 79 madrigueras de zorrillo pigmeo utilizando telemetría (29 pertenecientes a hembras y 50 a machos). Las madrigueras fueron excavaciones subterráneas con uno a cinco accesos localizadas en áreas el suelo o bajo árboles vivos o muertos probablemente construidas por otras especies y ocupadas por los zorrillos pigmeos. Los zorrillos mostraron que los zorrillos en varias ocasiones cada una de las madrigueras, pero no encontramos evidencia de ocupación simultánea de una madriguera por más de un zorrillo pigmeo. El análisis a nivel microhabitat mostró que los zorrillos pigmeos utilizan madrigueras al interior del bosque pero presentaban una gran flexibilidad en cuanto al uso del hábitat a este nivel con un elevado nivel de variación individual. A nivel macrohabitat no encontramos selección por parte de los zorrillos para colocar sus madrigueras en el bosque tropical deciduo o el bosque tropical semideciduo, sin embargo no se encontraron madrigueras en áreas fuera del bosque. Esta observación sugiere que los zorrillos pigmeos presentan una fuerte asociación a las áreas de bosque tropical de la costa del Pacifico mexicano. Las elevadas tasas de deforestación de los bosques tropicales en la costa de Jalisco, podrían reducir la existencia de sitios potenciales para madrigueras de zorrillo pigmeo, exponiéndolos probablemente a condiciones ambientales adversas y depredación. [source] | |||||||||||||||||||