Corridor Geometry Research Articles

Geomorphic context in process‐based river restoration

AbstractProcess‐based river restoration seeks to restore processes such as channel‐floodplain connectivity that create and maintain river corridor functions. Process‐based restoration can fail to produce the desired results if geomorphic context is not effectively incorporated into restoration design. Geomorphic context of a river reach refers to the controls on contemporary river form and process. Controls at the catchment‐ to reach‐scale include geologic history, biophysical characteristics, legacies of past human alterations, position within the river network, river corridor geometry, base level stability, disturbance regime, and contemporary human alterations of the river corridor. We conceptualize a river corridor as reflecting the interactions among fluxes of material and the geomorphic context. We discuss how an understanding of geomorphic context can be used to select a restoration approach and provide examples of how restoration can fail to achieve desired outcomes when geomorphic context is not considered. Within the toolbox of methods used to implement process‐based restoration, we differentiate the alteration of inputs to the river corridor and fluxes of material through the corridor from alteration of form and/or connectivity within the river corridor. Historical, biotic, geologic/geomorphic, and reference sites can be used to inform process‐based restoration targets. Restoration is strongly influenced by human perceptions of what is appropriate and achievable at a site and diverse communities influencing restoration at a site may differ in their perceptions. Geomorphically based conceptual guidelines, such as the River Styles Framework, provide an effective platform for incorporating an understanding of geomorphic context into process‐based river restoration.

Effects of the body force on the pedestrian and the evacuation dynamics

The Social Force Model (SFM) is a suitable model for describing crowd behaviors under emotional stress. This research analyzes the role of the body force in the original SFM. We focused on the parameter associated with the body stiffness (kn) and its impact on the pedestrian dynamics for two different geometries: bottlenecks and corridors. Increasing kn produces opposite effects on the crowd dynamics for each geometry: an increase of the crowd velocity for bottlenecks, and a decrease for corridors. The former reflects the fact that an increase in the stiffness reduces the overlap between pedestrians and, as a consequence, the sliding friction is diminished. This phenomenon reduces the number of blocking clusters close to the exit door. In the case of the corridor, instead, due to the confining walls, the pedestrians get tight into a lattice-like configuration due to space limitations. The friction interaction with the walls determines the velocity of the whole crowd along the corridor. Additionally, the corridor geometry generates a flux slowing down for very crowded environments, as observed in many real-life situations. We also explored the contact forces parameter values (body force and friction coefficients) and tuned them to reproduce the qualitative behavior of the empirical fundamental diagram.

Towards Scalable Indoor Map Construction and Refinement using Acoustics on Smartphones

The lack of digital floor plans is a huge obstacle to pervasive indoor location based services (LBS). Recent floor plan construction work crowdsources mobile sensing data from smartphone users for scalability. However, they incur long time (e.g., weeks or months) and tremendous efforts in data collection. In this paper, we propose BatMapper , which explores a previously untapped sensing modality–acoustics–for fast, fine grained, and low cost floor plan construction. We design sound signals suitable for heterogeneous microphones on commodity smartphones, and acoustic signal processing techniques to produce accurate distance measurements to nearby objects. We further develop robust probabilistic echo-object association, recursive outlier removal, and probabilistic resampling algorithms to identify the correspondence between distances and objects, thus the geometry of corridors and rooms. We compensate minute hand sway movements to identify small surface recessions, thus detecting doors automatically. Experiments in real buildings show BatMapper achieves $1-2$ 1 - 2 $cm$ c m distance accuracy in ranges up around 4 $m$ m ; a $2\sim 3$ 2 ∼ 3 minute walk generates fine grained corridor shapes, detects doors at 92 percent precision and $1\sim 2$ 1 ∼ 2 $m$ m location error at 90-percentile; and tens of seconds of measurement gestures produce room geometry with errors $ 0 . 3 $m$ m at 80-percentile, at $1-2$ 1 - 2 orders of magnitude less data amounts and user efforts.

Respecting a speed limit and its effectiveness in a traffic calming zone

The purpose of the study was to test the level of respecting the speed limit by drivers of vehicles in a traffic-calming zone that was not formally designated, located in a part of an old city in a middle of the Polish city. Due to the historic assets in that location, the applied means of traffic calming included only legal-organizational means, i.e. local speed limit signs. The analysis was carried out of vehicles speed in selected measuring sections; next, the level of respecting speed limits by drivers was determined. The results proved that just installing the speed limit signs at entrances to zones or at priority to the right intersections are insufficient to obtain the required speeds. The tests revealed that in all tested sections, drivers exceeded the speed limit of 30 km/h. An average speed varied from 32.1 km/h to 37.1 km/h, with the 85% quantile of speed amounting from 36.1 km/h to 42.7 km/h. A large percentage of drivers who exceed the speed limit was recorded, which was from 35% to 90%. The lowest percentage of drivers exceeding the maximum speed was recorded in sections where the surface was made of cobblestone (only 10%). This stemmed from the fact that in order to obtain the driving comfort, the drivers were forced to reduce the speed significantly. The results of tests show explicitly that in order to obtain desired traffic conditions from the safety perspective, it is necessary to apply physical means of traffic calming that force drivers to reduce speed. Such measures should include: an adjustment of the traffic corridor geometry in a general layout, narrowing a lane, speed bumps, raised speed tables at intersections, and raised pedestrian crossings. The applied traffic calming measures, including but not limited to areas that are subjects to the conserver’s supervision, should meet high functional, engineering, and visual standards, and be a harmonious part of the historic surrounding.

Impact of Phase Sequence on Cycle Length Resonance

The concept of resonant cycle length, that there are certain cycle lengths that may provide excellent progression owing to corridor geometry and other factors, has some currency as a potential strategy for cycle length selection. Past studies have identified resonant cycles under certain conditions and demonstrated benefits from use of the strategy as a means of selecting cycle length. The present study revisited the concept in application to flow-based models of traffic signal performance, highlighting the impact of phase sequence optimization. The phenomenon of cycle length resonance was explored for corridors with equal and randomly generated spacing between intersections, and finally for a field-calibrated corridor. Under each scenario, the performance of different cycle lengths was explored under two optimization strategies: optimization of only offsets, and optimization of both offsets and phase sequence. It was found that phase sequence has a substantial impact on the performance of coordination. Optimized phase sequences were found to yield 8% to 14% improvement in performance compared with use of the default sequence. For corridors where a resonant cycle length was evident, when phase sequences could also be adjusted, the poorer performance of non-resonant cycle lengths could be mitigated by optimizing phase sequence. Although use of a resonant cycle length is likely to yield good performance for some corridors under appropriate conditions, the use of a phase sequence optimization strategy is likely to have a strong impact on most corridors, and could be more impactful than selection of a resonant cycle length.

Optimizing the Geometry of Wildlife Corridors in Conservation Reserve Design

Wildlife corridors are often used to connect critical habitat for species protection. Mixed integer programming models have been used in the past to create wildlife corridors, but they lack the capacity to control corridor geometry. We propose an approach that employs path planning techniques from artificial intelligence to account for and control corridor geometry, such as width and length. By combining path planning with network optimization, our approach allows the user to control and optimize the geometric characteristics of wildlife corridors. We illustrate our approach on two realistic landscapes and present numerical results on several computer-generated landscapes. The computational results indicate that this approach is efficient and can address problems controlling corridor geometry that were previously thought intractable. The approach has potential applications in such areas as the selection of routes or barrier construction problems, an example of which is firebreak design.Data are available at https://doi.org/10.1287/opre.2018.1758 .

An orientation estimation algorithm based on multi-source information fusion

With the development of the Internet-of-Things, urgent market demands have also provided a huge development space for indoor pedestrian positioning systems (IPPS). Complementary filters (CF), Kalman filters and their various modifications are usually used to estimate the orientation in foot-mounted IPPS. However, the accuracy of the orientation is still low because of various types of electromagnetic interference and the diversity of pedestrians’ motion states. In this paper, an orientation estimation algorithm is proposed innovatively. First, the nine-axes inertial/magnetic sensors are calibrated using the error model of micro-electromechanical systems sensors. Then, the adaptive complementary filtering (ACF) algorithm is used to determine short- and medium-term orientation by making full use of the complementary error characteristics of the nine-axes inertial/magnetic sensors; the corridor geometry in rectangular buildings can also be regarded as prior information. Finally, the fusion of the orientation calculated by the ACF algorithm and the prior information is realized by the extended Kalman filter algorithm, which can improve the long-term accuracy of the orientation. To verify the performance of the proposed algorithm, a foot-mounted IPPS is set up based on MPU9250, and the raw data from the sensors are calibrated and imported into MATLAB for processing and analysis. The root mean square error of the orientation is less than 1.5° using the proposed method, and the results show that the proposed algorithm significantly surpasses other state-of-the-art algorithms, contributing to higher accuracy of orientation.

Assessing the impact of closely-spaced intersections on traffic operations and pollutant emissions on a corridor level

Traffic lights or roundabouts along corridors are usually installed to address location-specific operational needs. An understanding of the impacts on traffic regarding to highly-congested closely-spaced intersections has not been fully addressed. Accordingly, consideration should be given to how these specific segments affect corridor performance as a whole.One mixed roundabout/traffic light/stop-controlled junctions corridor was evaluated with the microscopic traffic model (VISSIM) and emissions methodology (Vehicle Specific Power – VSP). The analysis was focused on two major intersections of the corridor, a roundabout and a traffic light spaced lower than 170m apart under different traffic demand levels. The traffic data and corridor geometry were coded into VISSIM and compared with an alternative scenario where the traffic light was replaced by a single-lane roundabout. This research also tested a method to improve corridor performance and emissions by examining the integrated effect of the spacing between these intersections on traffic delay and vehicular emissions (carbon dioxide, monoxide carbon, nitrogen oxides, and hydrocarbons). The Fast Non-Dominated Sorting Genetic Algorithm (NSGA-II) was used to find the optimal spacing for these intersections.The analysis showed that the roundabout could achieve lower queue length (∼64%) and emissions (16–27%, depending on the pollutant) than the traffic light. The results also suggested that 200m of spacing using the best traffic control would provide a moderate advantage in traffic operations and emissions as compared with the existing spacing.

Empirical Studies on Impacts of Obstacle inside Corridor on Pedestrian Flow

Empirically, pedestrian motion can be studied at various levels. At the macroscopic level one may study the basic flow parameters (like speed and density) of pedestrian motion, at the microscopic level one may track the paths followed by individual pedestrians while moving. Whereas, at a mesoscopic level one can study pedestrian motion by concentrating on how the flow parameters change spatially and temporally. Such studies help in understanding pedestrian flow at a reasonably fundamental level and also aid in understanding how various geometric features impact pedestrian motion. In this study, macroscopic and mesoscopic level data are collected from various experiments aimed at understanding impact of corridor geometry on uni–directional and bi– directional pedestrian flow. First one is a “basic uniform width” or a “reference” corridor. To impose geometric variations in the corridor two different procedures are adapted, i) narrowing (symmetric as well as asymmetric) of the corridor, and ii) partial bifurcation of the corridor (by placing obstacle for a certain distance inside the corridor). Experimental details and results on narrowed corridors and their comparisons with the “reference” corridor are presented in another earlier paper. This study concentrates on experimental details and results on partially bifurcated corridor and their comparisons with the “reference” corridor. These experiments are intended to observe the lateral and longitudinal variations in density and longitudinal variations in speed due to the impact of various corridor geometry when pedestrians can walk side–by–side as well as overtake one another. To understand the lateral and longitudinal variations in density some crucial parameters are introduced in this study, which prove to be good quantitative measure in this regard. Results both on density and speed accentuate the fact that partial bifurcation in the corridor adversely impacts pedestrian flow inside the corridor.

Computer Planning in the Research, Analysis and Design of Skull Base Surgical Approaches

Objectives: No integrated system exists to plan skull base operations, nor to design and test new surgical approaches. Our objective was to develop a method of surgical planning, selection of optimal surgical approach(es), and design of surgical corridor geometry using a computer model that creates physical models for iterative optimization, pre-surgery approach trial, and surgical education and evaluation. Methods: The analysis was applied to a specific clinical scenario of accessing the lateral cavernous sinus. A computer analysis was performed to select the optimal surgical approach portal. Once derived, the specific geometry of the surgical corridor was designed for optimal visualization and instrumentation, while applying retraction limit constraints on specific soft tissue structures. A physical model of the surgical pathway was produced for testing, and the resultant approach was performed on 4 cadaver specimens. Results: A lateral retrocanthal transorbital approach was selected based on computer analysis. The pathway length was 55.6 mm (SD: 4.4) to 67.1 mm (SD: 0.7), retraction distance away from orbital rim was 8.2 mm (SD: 0.1), corridor volume was 2,751 mm3 (SD: 736), and cross sectional areas at the portal entrance and greater wing of sphenoid were 127 mm2 (SD: 19.2) and 210 mm2 (SD: 14.0), respectively. Dry lab and cadaver testing validated the computer planning analysis. Conclusions: A method was created and validated to determine the optimal surgical approach and pathway geometry for accessing a specific target pathology. It was robust and is applicable to many clinical scenarios. Initial evaluation in surgical cases has begun.

CT-based 3-D visualisation of secure bone corridors and optimal trajectories for sacroiliac screws

Sacroiliac screw (SI) fixation represents the only minimally invasive method to stabilise unstable injuries of the posterior pelvic ring. However, it is technically demanding. The narrow sacral proportions and a high inter-individual shape variability places adjacent neurovascular structures at potential risk. In this study a CT-based virtual analysis of the iliosacral anatomy in the human pelvis was performed to visualise and analyse 3-D bone corridors for the safe placement of SI-screws in the first sacral segment.Computer-aided calculation of 3-D transverse and general SI-corridors as a sum of all inner-bony 7.3-mm screw positions was done with custom-made software algorithms based on CT-scans of intact human pelvises. Radiomorphometric analysis of 11 CT-DICOM datasets using the software Amira 4.2. Optimal screw tracks allowing the greatest safety distance to the cortex were computed. Corridor geometry and optimal tracks were visualised; measurement data were calculated.A transverse corridor existed in 10 pelvises. In one dysmorphic pelvis, the pedicular height at the level of the 1st neural foramina came below the critical distance of 7.3mm defined by the outer screw diameter. The mean corridor volume was 45.2cm3, with a length of 14.9cm. The oval cross-section measured 2.8cm2. The diameter of the optimal screw pathway with the greatest safety distance was 14.2mm. A double cone-shaped general corridor for screw penetration up to the centre of the S1-body was calculated bilaterally for every pelvis. The mean volume was 120.6cm3 for the left side and 115.8cm3 for the right side. The iliac entry area measured 49.1 versus 46.0cm2. Optimal screw tracks were calculated in terms of projected inlet and outlet angles. Multiple optimal screw positions existed for each pelvis.The described method allows an automated 3-D analysis with regard to secure SI-screw corridors even with a high number of CT-datasets. Corridor visualisation and calculation of optimal screw tracks trains the visual thinking of the surgeon and can improve pre-operative planning. Prospectively, the introduced method can be implemented in computer-assisted surgery applications involving pelvic trauma.

Roundabouts in Signalized Corridors

Typically, roundabouts in the United States are installed at isolated intersections to address location-specific safety or operational needs. The use of roundabouts in signalized corridors, however, has not been well evaluated. It is commonly believed that roundabouts can improve traffic flow and travel speeds along an urban corridor by reducing delay caused by idling at intersections. Concern exists, however, that a roundabout in a coordinated signalized corridor will disrupt continuous traffic flow: downstream signals can more efficiently process vehicles in a platoon, and roundabouts disperse rather than form platoons. Roundabouts also can discharge vehicles more efficiently when traffic arrives randomly. Thus unnecessary queuing may result when roundabouts are downstream of signalized intersections. Since little research was available to compare the traffic flow impacts of roundabouts within a signalized corridor, two case studies were evaluated with the microscopic traffic simulation package, VISSIM. A roundabout and two signalized alternatives, as well as a roundabout and a four-way, stop-controlled alternative, were compared at intersections along signalized corridors in Ames, Iowa, and Woodbury, Minnesota, respectively. The traffic data and corridor geometry were coded into VISSIM, and traditional intersection traffic control within the corridors was compared with a scenario that had a two-lane roundabout. With the microsimulation software, average travel time, stopped delay, and average delay for the entire corridor were compared.

Corridor navigation of the mobile robot using image based control

In this paper, the wall following navigation algorithm of the mobile robot using a mono vision system is described. The key points of the mobile robot navigation system are effective acquisition of the environmental information and fast recognition of the robot position. Also, from this information, the mobile robot should be appropriately controlled to follow a desired path. For the recognition of the relative position and orientation of the robot to the wall, the features of the corridor structure are extracted using the mono vision system, then the relative position, the offset distance and steering angle of the robot from the wall, is derived for a simple corridor geometry. For the alleviation of the computation burden of the image processing, the Kalman filter is used to reduce search region in the image space for line detection. Next, the robot is controlled by this information to follow the desired path. The wall following control scheme by the PD control scheme is composed of two control parts, the approaching control and the orientation control, and each control is performed by steering and forward-driving motion of the robot. To verify the effectiveness of the proposed algorithm, the real time navigation experiments are performed. Through the result of the experiments, the effectiveness and flexibility of the suggested algorithm are verified in comparison with a pure encoder-guided mobile robot navigation system.