Open Corridors Research Articles

Environment specific TCP upstream throughput models in IEEE802.11b WLAN

This paper presents our study on environment based dependence of TCP Upstream Throughput (TCPupT) on signal to noise ratio (SNR) for a single user in an IEEE 802.11b Wireless Local Area Network (WLAN). Small offices, open corridors and free space environments were studied using an infrastructure based network for different quality of service (QoS) traffic. Environment based Models that predict TCPupT directly from SNR for different signal categories were statistically generated, validated and compared with similar models that were earlier developed without considering specific environments. The first type of models developed in this work were developed from all data specifically collected from each environment while the second type of models were developed by first categorizing the data in each specific environment into different signal categories and then models were statistically generated for each signal category before combining them into one model equation. At the stated levels of significance and the different degrees of freedom, the developed models were accepted at 1% (for F test) and 0.5% (for T test). From the RMS errors computed, the specific environment based models developed in this work were more accurate (as they showed lower RMS errors compared with earlier similar models) in predicting TCPupT in IEEE 802.11b WLAN for a single user on the network. It was also observed that the second type of models were found to be more accurate having shown lower RMS errors.Keywords: TCP Upstream throughput, Signal to noise ratio, environment based empirical model,IEEE802.11b, WLANs

Multiple users round trip time CDF probability models in IEEE802.11b WLANS

Multiple Users Round Trip Time Cumulative Distribution Function Probability Models (MURTTCDFPM) in IEEE 802.11b Wireless Local Area Networks (WLANs) have been presented in this paper. To develop the models, field and validation data were collected for various Quality of service (QoS) traffic in three different environments namely: open corridor, small offices and free space for an infrastructure based IEEE802.11b WLAN. The data was categorised into four signal ranges namely: all signals considered, strong signals, grey signals and weak signals. By assuming a normal distribution for the collected field data, MURTTCDFPM were developed and correction factors were applied to improve their prediction accuracy. The MURTTCDFPM developed were compared with existing Single user Round trip time (RTT) Cumulative distribution function (CDF) probability models. The results and the tests conducted show that the MURTTCDFPM have good performances as root mean square (RMS) errors <11.9274495% were observed.

Multiple users round trip time models in IEEE 802.11b WLANS

The dependence of Round Trip Time (RTT) on Signal to Noise Ratio (SNR) for multiple users in an IEEE 802.11b Wireless Local Area Network (WLAN) was studied in this work. Data collected in open corridor, small offices and free space environments in an infrastructure based network (where different quality of service traffic were continuously being sent by multiple users) was used to develop and validate Multiple User RTT models predicted from computed SNR.The models were also compared with single user models earlier developed. The tests results show that for multiple users on the network, RTT can be predicted from the computed SNR with reasonable accuracy as the models passed the F and T test at 0.1% level of significance and RMS errors of less than 867.378214ms were observed. During network design and installation, these models provide useful tools that can enable IEEE 802.11b WLAN installers to make fast and better informed RTT decisions.Keywords: Round trip time, Signal to noise ratio, empirical models, Wireless Local Area Networks

Pleistocene range expansions might explain striking disjunctions between eastern Brazil, Andes and Mesoamerica inLeandras.str. (Melastomataceae)

AbstractLeandras.str. clade has around 200 species nearly restricted to eastern Brazil. Most species in this group are narrow endemics, but a few present striking disjunct distributions between eastern Brazil and Andes or Mesoamerica. Given the predominantly “montane” distribution observed in mostLeandras.str., we hypothesized that cyclical range expansions during colder Pleistocene periods, followed by local extinctions during warmer interglacial periods, could have shaped the distribution of the disjunct species in this clade. In order to gather support for this biogeographical scenario in a phylogenetic framework, the species that occur outside eastern Brazil were identified, ages of the dispersal events estimated, climatic niche models for the disjuncts were generated, and the climatic envelope of these species compared. Our results place all dispersal events from eastern Brazil to Andes or Mesoamerica during the Pleistocene. Climatic niche modeling indicates a potential range expansion during the Pleistocene colder times for the disjunct species. Although the surpassing of the “dry diagonal” could have been facilitated during glacial periods, this open corridor is an effective barrier forLeandra, given the reduced number of species that dispersed beyond an eastern Brazilian origin. Additionally, the disjunct species do not present significant differences in their climatic envelopes to the non‐disjunct species. Our results provide support to a short‐dispersion/stepping‐stone migration scenario to account for the observed disjunctions in this clade. Range expansions during Pleistocene colder periods followed by local extinctions during interglacial periods could have shaped the distribution ofLeandras.str.

Soil volume restrictions and urban soil design for trees in confined planting sites

Urban trees often suffer from poor soil conditions, compromising their health and safety and raising management issues. In compact development areas, planting sites are beset by critical physical soil constraints, especially confined soil volume on narrow roadsides. These include internal (micro-scale) restrictions due to compaction and excessive coarse fractions such as gravels, and external (macro-scale) restrictions due to limited soil depth and width. Soil area provision (SAP) is assessed based on the moisture need of trees. A creative soil design scheme is proposed to expand soil volume, based on the principle of soil volume sharing, subsurface soil conduits, and subsurface soil corridors supplementing the routine open soil corridor. SAP could extend from the narrow footpath to the adjoining carriageway as a soil peninsula and green space as offset soil volume. The study aimed at knowledge exchange among science, policies, and practices, with implications for the sustainable management of many roadside trees in cities.

Relation of lumbar sympathetic chain to the open corridor of retroperitoneal oblique approach to lumbar spine: an MRI study.

Retroperitoneal oblique approach to lumbar spine used surgical corridor between psoas muscle and aorta for exposure to anterior part of lumbar spine. Lumbar sympathetic chain (LSC) runs in the corridor to make it a structure at risk of injury. Does LSC relationship with surgical corridor for minimally invasive retroperitoneal anterolateral oblique approach change in different intervertebral disc level? Left LSC was identified in axial magnetic resonance imaging images at L2-3, L3-4 and L4-5 intervertebral disc levels of 144 patients. Distances between LSC and left psoas muscle and aorta were recorded. Mean age of the patients was 62.3years. LSC was identifiable in 90.9% of levels. Distance between LSC and psoas muscle at L2-3, L3-4 and L4-5 was 4.0mm, 4.7mm and 5.2mm. Statistical difference was found between L2-3 and L4-5 level (p = 0.006). Distance between LSC and aorta at each level was 12.4mm, 12.3mm and 10.6mm without statistical difference. In non-scoliosis group distance between LSC and psoas muscle at each level was 3.1mm, 3.3mm and 4.0mm. Statistical difference was found between L2-3 and L4-5 level (p = 0.012) and between L3-4 and L4-5 level (p = 0.041). Distance between LSC and aorta at each level was 11.9mm, 11.4mm and 10.2mm. Statistical difference was found between L2-3 and L4-5 disc level (p = 0.039). LSC moves away from psoas muscle and becomes closer to aorta in L4-5 disc level. These slides can be retrieved under Electronic Supplementary Material.

Disperse or die: Colonisation of transient open habitats in production forests is only weakly dispersal-limited in butterflies

Evaluating ecological processes that assemble local animal communities from available species pools has remained a challenging task. At a time of drastic decline of natural and seminatural grasslands, contemporary production forests provide various novel types of open spaces (clear-cuts, power line corridors, etc.) that are potentially suitable habitats for many grassland species, such as butterflies. On the other hand, grassland butterflies are known to perceive forest as a dispersal barrier, potentially limiting the utility of such alternative habitats. We evaluated the role of dispersal limitation in structuring local butterfly assemblages in conventionally managed forest landscapes in which clear-cutting generates varyingly isolated transient open habitats within the forest matrix. We compared butterfly species richness and composition in clear-cuts at opposite ends of a connectivity gradient: sites completely surrounded by forest (isolated clear-cuts) vs. sites connected to the network of other forest clearings by open corridors (non-isolated clear-cuts). We found only a slight difference in the species richness between isolated and non-isolated clear-cuts, both when all open-habitat species and when the subset of grassland species was compared. The frequencies of individual butterfly species in isolated and non-isolated sites were strongly correlated, regardless of their presumed dispersal ability. Our results indicate that, in large areas of production forests in Northern Europe, the formation of local butterfly assemblages is not significantly limited by dispersal. This study contributes to emerging evidence that open spaces in managed forest landscapes can be regarded as alternative habitat for a substantial share of species traditionally considered to be associated with grasslands.

Dynamical transition on the periodic Lorentz gas: Stochastic and deterministic approaches.

The effect of dynamical properties of the periodic Lorentz gas on the autocorrelation function and diffusion coefficient are investigated in various geometric transitions between billiards without horizon and infinite horizon. Numerical simulations are performed using a double square lattice which permits us to isolate different types of corridors and to describe the individual effects of each corridor. The results are compared with a stochastic model based on a escape-rate formalism which reveals the sensibility of the diffusion coefficient and clarifies the role of the open corridors mechanism on the dynamical transitions.

Choroid plexus-cerebrospinal fluid route for monocyte-derived macrophages after stroke

BackgroundChoroid plexus (CP) supports the entry of monocyte-derived macrophages (MDMs) to the central nervous system in animal models of traumatic brain injury, spinal cord injury, and Alzheimer’s disease. Whether the CP is involved in the recruitment of MDMs to the injured brain after ischemic stroke is unknown.MethodsAdult male C57BL/6 mice were subjected to focal cortical ischemia by permanent occlusion of the distal branch of the right middle cerebral artery. Choroid plexus tissues were collected and analyzed for Vcam1, Madcam1, Cx3cl1, Ccl2, Nt5e, and Ifnγ expression at different timepoints after stroke using qPCR. Changes of MDMs in CP and cerebrospinal fluid (CSF) at 1 day and 3 days after stroke were analyzed using flow cytometry. Infiltration of MDMs into CP and CSF were validated using β-actin-GFP chimeric mice and Fgd5-CreERT2 x Lox-stop-lox-Tomato mice. CD115+ monocytes were isolated using a magnetic cell separation system from bone marrow of Cx3cr1-GFP or wild-type C57BL/6 donor mice. The freshly isolated monocytes or M2-like MDMs primed in vitro with IL4 and IL13 were stereotaxically injected into the lateral ventricle of stroke-affected mice to trace for their migration into ischemic hemisphere or to assess their effect on post-stroke recovery using open field, corridor, and active avoidance behavioral tests.ResultsWe found that CP responded to cortical stroke by upregulation of gene expression for several possible mediators of MDM trafficking and, concomitantly, MDMs increased in CP and cerebrospinal fluid (CSF). We then confirmed that MDMs infiltrated from blood into CP and CSF after the insult using β-actin-GFP chimeric mice and Fgd5-CreERT2 x Lox-stop-lox-Tomato mice. When MDMs were directly administered into CSF following stroke, they homed to the ischemic hemisphere. If they had been primed in vitro prior to their administration to become M2-like macrophages, they promoted post-stroke recovery of motor and cognitive function without influencing infarct volume.ConclusionsOur findings suggest the possibility that autologous transplantation of M2-like MDMs into CSF might be developed into a new strategy for promoting recovery also in patients with stroke.

Optimization of thermal and daylight performance of school buildings based on a multi-objective genetic algorithm in the cold climate of China

A high demand for heating energy in winter, overheating in summer and visual discomfort are important issues in school buildings in the cold climate of China. This study presents the use of simulation–optimization tools to find the optimal trade-off between minimizing energy use for heating and lighting, reducing summer discomfort time and maximizing the Useful Daylight Illuminance (UDIavg, between 100 and 2000lx). Different spatial configurations were investigated, including a single-sided open corridor type, a single-sided enclosed corridor type and a double-sided corridor type school. The following passive design parameters were considered in the optimization analysis: orientation, room depth and corridor depth, window-to-wall ratio of different interfaces, glazing materials and shading types.The results of the optimization study show that the energy demand for heating and lighting can be reduced by 24–28% and summer thermal discomfort by 9–23% while the UDIavg (100–2000lx) can simultaneously increase by 15–63%. Considering all three aspects, the double-sided enclosed corridor type performs best due to its energy performance while the one-sided enclosed corridor type is the least suitable for the cold climate because of its relatively poor visual comfort quality. In addition, the passive design parameters should be carefully considered as each spatial configuration has its own optimal passive design parameters.

No Panacea Garden

Essay ExcerptsThree of the seven distinguished researchers whose autobiographical chapters (Berliner, 2016; Sternberg, 2016; Sweller, 2016) I edited, and one that is in process (Gordon, in press), indicate that they were poor or indifferent students early in their academic careers. That is also true of me; so five of the first seven scholars in the Acquired Wisdom series were poor students. I did not explicitly mention my studying difficulties in this chapter because they had already been described in my memoir about how my family found safe haven from the Holocaust in Shanghai, China, during World War II (Tobias, 2009). It may be useful to examine my difficulties and how they relate to educational practice and concepts in the contemporary educational psychology literature. The late Dick Snow, a friend and colleague at Stanford, once commented that research on instructional innovations seemed to him like a random walk through the panacea garden. I have become sceptical of any instructional development, theory, or instructional method that is expected to improve learning for all students in all subjects. I have lived through prior panaceas like programmed and computer assisted instruction, multimedia education, computer games, and educational movements such as progressive, competency based, open corridor, and inquiry education, and the current panacea - constructivist instruction - from all of which I learned something. There are no panaceas that will easily improve learning for everyone, because good instruction is hard work and difficult to do. [Download the PDF ]

Measurement and modelling of TCP downstream throughput dependence on SNR in an IEEE802.11b WLAN system

This paper presents our study on the dependence of TCP downstream throughput (TCPdownT) on signal to noise ratio (SNR) for multiple users in an IEEE 802.11b Wireless Local Area Network (WLAN) system. The study was carried out in small offices, open corridors and free space environments using an infrastructure based IEEE 802.11b WLAN while transmitting different quality of service (QoS) traffic all corresponding to different wireless multimedia tags. Models describing TCPdownT against SNR for different signal categories were statistically generated and validated. Our findings show a large variation in the throughput behaviour of the IEEE 802.11b WLAN system for the different categories of signals. We observed RMS errors of 0.938012Mbps, 1.047012Mbps, 0.65833Mbps and 0.452927Mbps for the general (all SNR) model, strong signals model, grey signals model and weak signals model respectively which were much lower than that of similar models with which they were compared. Comparing our results with a previous work on TCP upstream throughput showed that it is more accurate to investigate upstream and downstream throughput separately. Our models enable network designers and installers to predict the TCPdownT without the need to measure additional parameters other than the observed SNR which is already part of the normal network installation process.

Radio Frequency Mapping using an Autonomous Robot: Application to the 2.4 GHz Band

Radio signal strength measurement systems are essential to build a Radio Frequency (RF) mapping in indoor and outdoor environments for different application scenarios. This paper presents an autonomous robot making the construction of a radio signal mapping, by collecting and forwarding different useful information related to all access point devices and inherent to the robot towards the base station. A real case scenario is considered by measuring the RF field from our department network. The RF signal mapping consistency is shown by fitting the measurements with the radio signal strength model in two-dimensional area, and a path-loss exponent of 2.3 is estimated for the open corridor environment.

Continental gateways and the dynamics of mammalian faunas

Continental gateways occur where mountainous topography interacts with changing climate and sea level to open or close dispersal corridors. The interaction of permeable or impermeable montane barriers with changing or stable climate yields four biogeographic states, each associated with changes in diversification rates and ecological structure of faunas. For example, permeable montane barriers and climatic stability result in low rates of immigration and extinction, elevated endemic speciation, and stable ecological structure. Three examples from the mammalian fossil record test these scenarios. (1) In Miocene faunas of Pakistan, immigration rates peaked and faunal proportions changed during an interval of cooling and open corridors. (2) In Miocene faunas of Spain, elevated extinction and origination rates and changing trophic structure occurred during regional aridification with open corridors. (3) In Quaternary faunas of South Africa, ungulates experienced range reductions and elevated extinction during the transition from glacial to interglacial climates as corridors closed.

Optimization of Wind Driven Rain Barrier for Tropical Natural Ventilated Building

Wind Driven Rain (WDR) is an inherent problem especially on open corridors and open areas like courtyard, balconies and terraces of naturally ventilated tropical buildings. The WDR can cause the building floor to be slippery and even flooding during heavy rain and strong wind. It can also eventually caused damages on building materials if exposed over a long period of time. Unfortunately, until to date there are not many researches conducted on WDR in tropical natural ventilated buildings. An experimental and CFD simulation analyses were taken into consideration to predict the percentage of water on a floor of case study building. Different types of rain barrier designs have been proposed to reduce the amount of wind driven rain entering the building. The CFD simulation results showed that the water percentage on the floor caused by the wind driven rain can be reduced from 78% of the floor area to about 42% using titled overhang rain barrier design.

Tracking Algorithm Based on Channel Propagating Characteristic in Wireless Sensor Network

In order to improve the mobile node tracking accuracy of indoor environment, a mobile node tracking algorithm based on channel propagating characteristic is proposed. Channel propagation model is established by actual measurement and fitting analysis in three different scenarios, which included closed corridor, open corridor and laboratory. The anchor node periodically measures the RSSI of the beacons from mobile node, to estimate the coordinates of the mobile node location, speed and direction by using the Maximum Likelihood method and channel model. The simulation results prove that the proposed scheme is effective and can meet the real-time requirements of indoor localization.

Empirical investigation on the dependence of TCP downstream throughput on SNR in an IEEE802.11b WLAN system

The dependence of TCP downstream throughput (TCPdownT) on signal to noise ratio (SNR) in an IEEE802.11b WLAN system was investigated in various environments and varieties of QoS traffic. TCPdownT was measured for various SNR observed. An Infrastructure based IEEE802.11b WLAN system having networked computers on which measurement software were installed, was set up consecutively in various environments (open corridor, small offices with block walls and plaster boards and free space). Empirical models describing TCPdownT against SNR for different signal ranges (all ranges of signals, strong signals only, grey signals only and weak signals only) were statistically generated and validated. As the SNR values changed from high (strong signals) through low (grey signals) to very low (weak signals), our results show a strong dependence of TCPdownT on the received SNR. Our models showed lower RMS errors when compared with other similar models. We observed RMS errors of 0.6734791Mbps, 0.472209Mbps, 0.9111563Mbps and 0.5764460Mbps for general (all SNR) model, strong signals model, grey signals model and Weak signals model respectively. Our models will provide researchers and WLAN systems users with a tool to estimate the TCP downstream throughput in a real network in various environments by monitoring the received SNR.

Investigation on the Dependence of TCP Upstream Throughput on Snr for Single and Multiple Links in a Wlan System

An empirical investigation on the dependence of TCP upstream throughput (TCPupT) against signal to noise ratio (SNR) in an IEEE802.11b WLAN system was carried out in various environments and varieties of QoS traffic using an Infrastructure based IEEE802.11b WLAN system set up consecutively in various environments (open corridor, small offices with block walls or plaster boards and free space). Empirical models describing the TCPupT against SNR for different signal ranges (all signals, strong signals, grey signals and weak signals) were developed and validated for both single and multiple users on the network. Our results show a strong dependence of TCPupT on the received SNR which varied as the SNR values changed from high (strong signals) through low (grey signals) to very low (weak signals). Our models showed lower RMS errors when they and other similar models were compared with validation data. We observed RMS errors of 0.5605471Mbps, 0.4479389Mbps, 1.04536603Mbps and 0.5813471Mbps for the General, Strong signals, Grey signals and Weak signals models respectively for the single user scenario. We also observed RMS errors of 1.3319396Mbps, 0.9457431Mbps, 0.8092979Mbps and 0.4220292Mbps for the multiple users scenario. An appreciable difference was observed between the throughput behavior for single and multiple users on the network showing the inefficiency of the distributed coordination function and Point coordination function used in WLANs as access mechanisms. Our models will provide researchers and WLAN systems users with a tool to estimate the TCP upstream throughput in a real network in various environments by monitoring the SNR.

水俣市湯の鶴温泉における自炊宿の平面構成

In Yunotsuru spa there are four Japanese inns with self-cooking facilities, but only one of them does business still now. In the case of these Japanese inns, workers live in it. Although the space of visitors and workers is separated from bordering on the cooking space, the rooms equipped with water supply are shared in some cases. And in the habitation space, a kitchen is located in the lower-part-of-river side. In addition, the guest room faces the road through the open corridor. According to downsizing and removal of self-cooking facilities, rooms by common use also decreased.

Restoring habitat for the northern Idaho ground squirrel (Urocitellus brunneus brunneus): Effects of prescribed burning on dwindling habitat

Land use and fire exclusion have contributed to an increase in ponderosa pine (Pinus ponderosa) forest extent and density in west-central Idaho. Open areas within ponderosa pine forests are decreasing, thus reducing habitat for the endemic northern Idaho ground squirrel (NIDGS; Urocitellus brunneus brunneus). In 2000, the NIDGS was listed on the Endangered Species Act as threatened in part due to habitat loss. Therefore, recovery plans encourage the use of burning to expand meadows and open corridors. We gathered data on habitat attributes altered by prescribed fall burning at three sites selected for habitat restoration. Each site was divided into two units: a CONTROL unit occupied by the NIDGS and a BURN unit not occupied by the NIDGS. We sought to assess whether the prescribed fall burning fulfilled management goals and generated habitat features similar to CONTROL conditions that are suitable for the NIDGS. Data were collected before the fall prescribed burn and one and two years post-burn. Before the prescribed burn, BURN units had higher tree densities and canopy cover than CONTROL units; however, the prescribed fall burn did not reduce tree density or canopy cover one year later. Understory height in the BURN unit decreased slightly post-burn, approaching CONTROL conditions. Majority of understory characteristics were similar between CONTROL and BURN units before, one, and two years after the burn, but understory community structure remained strongly dissimilar. This study preliminarily examines NIDGS habitat and is the first paper to evaluate the effects of prescribed burning as restoration practices to create NIDGS habitat. Key habitat attributes associated with NIDGS presence include tree canopy cover, understory height and community structure, and litter depth. Management goals were not attained within the stated timeline, one year post-burn, or even two years after prescribed burn was implemented. Based on our results, managers should consider extending the timeframe for restoration goal achievement and perhaps modifying goals to include changes in tree canopy cover, understory height and community structure, and litter depth. Future efforts should monitor beyond two years post-fire, focus on long-term effects of prescribed burning, and examine how repeat burns may help attain habitat restoration goals.