Intersection Types Research Articles

Semantic subtyping for imperative object-oriented languages

Semantic subtyping is an approach for defining sound and complete procedures to decide subtyping for expressive types, including union and intersection types; although it has been exploited especially in functional languages for XML based programming, recently it has been partially investigated in the context of object-oriented languages, and a sound and complete subtyping algorithm has been proposed for record types, but restricted to immutable fields, with union and recursive types interpreted coinductively to support cyclic objects. In this work we address the problem of studying semantic subtyping for imperative object-oriented languages, where fields can be mutable; in particular, we add read/write field annotations to record types, and, besides union, we consider intersection types as well, while maintaining coinductive interpretation of recursive types. In this way, we get a richer notion of type with a flexible subtyping relation, able to express a variety of type invariants useful for enforcing static guarantees for mutable objects. The addition of these features radically changes the defi- nition of subtyping, and, hence, the corresponding decision procedure, and surprisingly invalidates some subtyping laws that hold in the functional setting. We propose an intuitive model where mutable record val- ues contain type information to specify the values that can be correctly stored in fields. Such a model, and the correspond- ing subtyping rules, require particular care to avoid circularity between coinductive judgments and their negations which, by duality, have to be interpreted inductively. A sound and complete subtyping algorithm is provided, together with a prototype implementation.

Type soundness for dependent object types (DOT)

Scala’s type system unifies aspects of ML modules, object- oriented, and functional programming. The Dependent Object Types (DOT) family of calculi has been proposed as a new theoretic foundation for Scala and similar expressive languages. Unfortunately, type soundness has only been established for restricted subsets of DOT. In fact, it has been shown that important Scala features such as type refinement or a subtyping relation with lattice structure break at least one key metatheoretic property such as environment narrowing or invertible subtyping transitivity, which are usually required for a type soundness proof. The main contribution of this paper is to demonstrate how, perhaps surprisingly, even though these properties are lost in their full generality, a rich DOT calculus that includes recursive type refinement and a subtyping lattice with intersection types can still be proved sound. The key insight is that subtyping transitivity only needs to be invertible in code paths executed at runtime, with contexts consisting entirely of valid runtime objects, whereas inconsistent subtyping contexts can be permitted for code that is never executed.

How to Think of Intersection Types as Cartesian Products

In their paper “Intersection types and lambda definability” [Bucciarelli, A., Piperno, A., Salvo I., Intersection types and lambda definability, MSCS03, 13 (1), pp. 15–53, (2003)] Bucciarelli, Piperno, and Salvo give a mapping of the strongly normalizable untyped terms into the simply typed terms via the assignment of intersection types. Here we shall both generalize their result and provide a converse. We shall do this by retracting untyped terms with surjective pairing onto untyped terms without pairing by using a special variant of Stovring's notion [Støvring, K., Extending the extensional lambda calculus with surjective pairing is conservative, LMCS2, pp. 1–14] of a symmetric term. The symmetric ones which have simple types with Cartesian products are precisely the ones which retract onto (eta expansions of) strongly normalizable untyped terms. The intersection types of the strongly normalizable terms are related to the simple types with products in that we just replace ∧ by Cartesian product and vice versa.

Classical Realizability in the CPS Target Language

Motivated by considerations about Krivine's classical realizability, we introduce a term calculus for an intuitionistic logic with record types, which we call the CPS target language. We give a reformulation of the constructions of classical realizability in this language, using the categorical techniques of realizability triposes and toposes.We argue that the presentation of classical realizability in the CPS target language simplifies calculations in realizability toposes, in particular it admits a nice presentation of conjunction as intersection type which is inspired by Girard's ludics.

Hierarchical Fusion Estimation for Clustered Asynchronous Sensor Networks

In this note, a hierarchical fusion estimation method is presented for clustered sensor networks with a very general setup where sensors (sensor nodes) and estimators (cluster heads) are allowed to work asynchronously with aperiodic sampling and estimation rates. A sequential measurement fusion (SMF) method is presented to design local estimators, and it is shown that the SMF estimator is equivalent to the measurement augmentation (MA) estimator in precision but with much lower computational complexity. Two types of sequential covariance intersection (CI) fusion estimators are presented for the fusion estimation. The proposed SCI fusion estimators provide a satisfactory estimation precision that is close to the centralized batch CI (BCI) estimator while requiring smaller computational burden as compared with the BCI estimator. Therefore, the proposed hierarchical fusion estimation method is suitable for real-time applications in asynchronous sensor networks with energy constraints. Moreover, the method is applicable to the case with packet delays and losses.

Disjoint intersection types

Dunfield showed that a simply typed core calculus with intersection types and a merge operator is able to capture various programming language features. While his calculus is type-safe, it is not coherent : different derivations for the same expression can elaborate to expressions that evaluate to different values. The lack of coherence is an important disadvantage for adoption of his core calculus in implementations of programming languages, as the semantics of the programming language becomes implementation-dependent. This paper presents λ_i: a coherent and type-safe calculus with a form of intersection types and a merge operator . Coherence is achieved by ensuring that intersection types are disjoint and programs are sufficiently annotated to avoid type ambiguity . We propose a definition of disjointness where two types A and B are disjoint only if certain set of types are common supertypes of A and B. We investigate three different variants of λ_i, with three variants of disjointness. In the simplest variant, which does not allow ⊤ types, two types are disjoint if they do not share any common supertypes at all. The other two variants introduce ⊤ types and refine the notion of disjointness to allow two types to be disjoint when the only the set of common supertypes are top-like . The difference between the two variants with ⊤ types is on the definition of top-like types, which has an impact on which types are allowed on intersections. We present a type system that prevents intersection types that are not disjoint, as well as an algorithmic specifications to determine whether two types are disjoint for all three variants.

Assessment of Drivers with Alzheimer's Disease in High Demand Driving Situations: Coping with Intersections in a Driving Simulator.

Intersections are one of the most complex and cognitively demanding driving situations. Individuals with dementia and, more precisely, Alzheimer’s disease (AD), may face additional challenges negotiating intersections given the nature of their cognitive decline, which often includes deficits of attention. We developed a comprehensive evaluation scheme to assess simulated driving performance at intersections. The evaluation scheme captured all types of errors that could occur during preparation (i.e., prior to the intersection), execution (i.e., during the intersection), and recovery (i.e., after the intersection). Using the evaluation scheme, intersection behaviour in a driving simulator among 17 drivers with mild AD was compared to that of 21 healthy controls. The results indicated that across all types of intersections, mild AD drivers exhibited a greater number of errors relative to controls. Drivers with mild AD made the most errors during the preparation period leading up to the intersection. These findings present a novel approach to analyzing intersection behaviour and contribute to the growing body of research on dementia and driving.

A new integrated GIS-based analysis to detect hotspots: A case study of the city of Sherbrooke

This paper proposes a two-step integrated method for identifying traffic accident (TA) hotspots on a roadway network. The first step includes a spatial analysis method called network kernel density estimation (KDE). The second step is a network screening method using the critical crash rate, which it described in the Highway Safety Manual (HSM). The method was examined by using three years of TAs (2011–2013) in Sherbrooke, Canada. The network KDE uses TAs to graphically display sites with a high crash density. Two different crash patterns were used for identifying these locations: (1) a crash pattern that includes three-year aggregated crash data, and (2) a crash pattern that involves three-year merged crash data. The results of the two crash patterns were evaluated based on a prediction accuracy index (PAI). It was found that the results obtained from the merged crash data outperformed the other. On the other hand, crash clustering in a site does not imply a site is hotspot and it is better to tested by other factors. High crash density locations were then tested by the critical crash rate, which helps to create an accurate comparison of sites. The importance of the critical crash rate is that it takes several factors into account such as the amount of exposure, the type of intersection, variance in crash data, etc. We realized that the hotspots determined using the two methods reflect very problematic locations and filter out the locations that do not have a problem. This approach could help transportation authorities and safety specialists to identify and prioritize sites that require more safety attention.

Comparative life-cycle assessment of conventional (double lane) and non-conventional (turbo and flower) roundabout intersections

This research studied and compared different construction techniques for the road subgrade, embankment and pavement of different types of roundabout intersections in order to assess their environmental sustainability. A Life Cycle Assessment (LCA) was carried out on double lane, turbo- and flower roundabouts.We considered virgin materials and reclaimed asphalt pavement (RAP) for the pavement construction. Also the environmental effects due to in situ lime stabilization of fine-grained soils were assessed in order to reduce the use of virgin material in road subgrades.The use of reclaimed asphalt pavement (RAP) can lead to a significant reduction in pollutant emissions and energy consumption (especially due to the lesser material transport) – though with a slightly different impact according to the different percentages employed – compared to the pavements constructed with virgin materials. The same consideration can be made for fine soils with in situ lime stabilization: on the one hand, the technique allows to improve significantly the mechanical properties of soils which would be otherwise dumped and, on the other, to provide considerable environmental benefits. The life cycle assessment of the pavement was carried out with the help of the PaLATE software (by comparing different maintenance scenarios) while emissions and energy consumption in the use phase at intersections were evaluated by means of closed-form models (to estimate vehicle delays and speeds of vehicles) and the COPERT software.Finally, the generalized costs covered in the whole life cycle of roundabouts (i.e. sum of construction, maintenance and environmental costs) were assessed and associated to the different construction options.

5-GHz Vehicle-to-Vehicle Channel Characterization for Example Overpass Channels

The overpass is a special over-road structure for vehicular travel, constituting one type of roadway intersection. Real-time communications between on- and under-overpass vehicles can contribute to effective vehicle-to-vehicle (V2V) communications, including, for example, optimal route selection and overpass accident warning messaging. Ensuring effective communication requires a quantitative characterization of the overpass propagation channel. In this paper, we provide measurement and analytical results for V2V propagation path loss and root-mean-square delay spread, and from these results, we develop tapped-delay line channel models that are applicable to the 5-GHz band for two example overpasses. These two example overpasses are termed i) one-lane metal-bottom overpass and ii) two-lane metal-bottom overpass. Due to the unique structure of the overpasses, we divide the radio propagation space around the overpass into four different areas: a two-ray area, a short-term partial-shadowing area, a (full) shadowing area, and a long-term partial-shadowing area. In the two-ray area, a line-of-sight (LOS) path and a ground-reflected path are the dominant propagation mechanisms, whereas in the other areas, the overpass body (floor, walls, and columns) attenuates the LOS signal. The accuracy of our measurement results and the developed channel model are verified by a geometry-based stochastic channel modeling approach, in which the height dimension is first introduced to characterize the diffraction phenomenon in V2V communication. The actual measurement and simulation results show good consistency.

Novel Intersection Type Recognition for Autonomous Vehicles Using a Multi-Layer Laser Scanner.

There are several types of intersections such as merge-roads, diverge-roads, plus-shape intersections and two types of T-shape junctions in urban roads. When an autonomous vehicle encounters new intersections, it is crucial to recognize the types of intersections for safe navigation. In this paper, a novel intersection type recognition method is proposed for an autonomous vehicle using a multi-layer laser scanner. The proposed method consists of two steps: (1) static local coordinate occupancy grid map (SLOGM) building and (2) intersection classification. In the first step, the SLOGM is built relative to the local coordinate using the dynamic binary Bayes filter. In the second step, the SLOGM is used as an attribute for the classification. The proposed method is applied to a real-world environment and its validity is demonstrated through experimentation.

Strong Normalization through Intersection Types and Memory

We characterize β-strongly normalizing λ-terms by means of a non-idempotent intersection type system. More precisely, we first define a memory calculus K together with a non-idempotent intersection type system K, and we show that a K-term t is typable in K if and only if t is K-strongly normalizing. We then show that β-strong normalization is equivalent to K-strong normalization. We conclude since λ-terms are strictly included in K-terms.

AN EVALUATION OF TURBO ROUNDABOUT PERFORMANCES: CASE STUDY OF THE CITY OF OHRID

The turbo roundabout is an innovative design of the two lane roundabout that has revolutionised roundabout design. According to the international research, it is determined that the turbo roundabout has a higher level of traffic safety because of the lower number of conflicts and the use of raised lane dividers. In addition, compared with the conventional two lane roundabout, turbo roundabout has higher capacity. Due to these advantages, the reconstruction of intersections into turbo roundabouts has become a kind of global trend nowadays. The first turbo roundabout in the Republic of Macedonia was designed in Skopje in 2011, without tracking the performances. This was exactly the motive to investigate the performances of this type of intersections. In this research three intersections in sequence located in Ohrid (two signalized and one non-signalized intersection) and the performances are determined for the current situation and the situation with increased flows by using the software tool SIDRA. A reconstruction of the intersections has been made into turbo roundabouts. The performances for two different cases (current situation and the situation with increased flows, with and without the pedestrians’ influence) are determined with the use of both VISSIM and analytical model by Brilon and Wu. The analysis has proven that with the input parameters, turbo roundabouts offer better performances compared to the existing intersections. Thus, the reconstruction of the intersections is justified.

Impact of intersection type and a vehicular fleet's hybridization level on energy consumption and emissions

A vehicle's energy consumption and emissions are two major constraints in sustainable development. Both of them have proportionally raised in recent decades with the exponential growth of world traffic demands. The reduction of road traffic-generated energy consumption and emissions have thus become unprecedentedly challenging and worth examining. This paper investigates energy consumption and environmental problems present at roundabout and signalized intersection to analyze the impact of the hybridization level's fleet and intersection type on vehicle consumption and pollution. Instantaneous fuel consumption and emission models coupled with simulation of urban mobility (SUMO) are in this study. The authors started with modeling energy consumption. Then, an emission model emissions from traffic (EMIT) was implemented to quantify vehicle emissions of CO2, CO and NOx. These models help investigate the influence of intersection type on energy consumption and environmental conditions. The authors implemented a signalized intersection and roundabout using SUMO. The input data are collected from the roundabout of Sousse (Tunisia) using video data collection. Since there is a lack of econometric models that emulate hybridized stream behavior near intersections, two energy consumption models for the roundabout and crossroad are developed using traffic flow and hybridization level as the input variables. Compared to crossroads, a roundabout can obtain more environmental improvements and substantial reductions in energy consumption and road traffic emissions.

Safety evaluation of continuous green T intersections: A propensity scores-genetic matching-potential outcomes approach

The continuous green T intersection is characterized by a channelized left-turn movement from the minor street approach onto the major street, along with a continuous through movement on the major street. The continuous flow through movement is not controlled by the three-phase traffic signal that is used to separate all other movements at the intersection. Rather, the continuous through movement typically has a green through arrow indicator to inform drivers that they do not have to stop. Past research has consistently shown that there are operational and environmental benefits to implementing this intersection form at three-leg locations, when compared to a conventional signalized intersection. These benefits include reduced delay, fuel consumption, and emissions. The safety effects of the conventional green T intersection are less clear. Past research has been limited to small sample sizes, or utilized only statistical comparisons reported crashes to evaluate the safety performance relative to similar intersection types. The present study overcomes past safety research evaluations by using a propensity scores-potential outcomes framework, with genetic matching, to compare the safety performance of the continuous green T to conventional signalized intersections, using treatment and comparison site data from Florida and South Carolina. The results show that the expected total, fatal and injury, and target crash (rear-end, angle, and sideswipe) frequencies are lower at the continuous green T intersection relative to the conventional signalized intersection (CMFs of 0.958 [95% CI=0.772–1.189], 0.846 [95% CI=0.651–1.099], and 0.920 [95% CI=0.714–1.185], respectively).

Noise level in the vicinity of signalized roundabouts

The analysis, assessment and estimation of noise levels in the vicinity of intersections is a more complex problem than a similar analysis for roads and streets. This is due to the varied geometry of the intersections, differences in the loads of individual movements, participation of heavy vehicles and mass transport vehicles, as well as the various types of traffic management and traffic control. This article analyses the influence of intersection type and traffic characteristics on the noise levels in the vicinity of classic channelized intersections with signalization, roundabouts and signalized roundabouts. Based on the conducted measurements, it has been established that, with comparable traffic parameters and the same distance from the geometric centre of the intersection, the LAeq value for signalized roundabouts is 2.5–10.8dB higher in comparison to classic channelized intersections with signalization and 3.3–6.7dB higher in relations to the analysed roundabout. Additionally the differences between LAeq levels at individual entries at the same signalized roundabouts may reach the value of approximately 4.5dB. Such situation is influenced by differences in the intersection geometry, diameter of the intersection’s central island, traffic flow type, traffic management at the entries and traffic volume, especially the amount and traffic movements of multiple axle heavy vehicles. These factors have been analysed in detail in relation to signalized roundabouts in this paper.

Traffic design and signal timing of staggered intersections based on a sorting strategy

A staggered intersection is a special type of intersection in a road network. Its geographical characteristics consist of two T-legged intersections that cause the lost time per cycle to become longer than at cross intersections under conventional signal control, thus leading to low intersection efficiency. This article shows that the problem can be eliminated at the left–right type of staggered intersection by channelization and signal phasing, based on a sorting strategy and pre-signal, which reduce the amount of lost time during the signal cycle using the split distance as the sorting area. VISSIM was used to model and analyze the proposed method as well as the conventional method for comparison purposes. The simulation revealed that the proposed method reduced the average delays and maximum queue lengths in each movement and for the entire intersection, both in the peak hours and in the off-peak hour.

Urban Real-Time Traffic Monitoring Method Based on the Simplified Network Model

In urban real-time traffic monitoring, due to the difficult of delay time acquisition at intersection, complicated calculation model, lead to inaccurate traffic discriminant. Aiming at this problem, it proposed a real-time traffic discriminant method based on the simplified network model. In traffic data collection various types of intersections are abstracted as a node in this method, and the delay time at intersection are included in the pasting time of connected roads, then conduct back-stepping calculated according to different types of nodes at monitoring, obtained the traffic conditions of regular road, rotary road and intersection, thus realize real-time monitoring. Finally, to verify the validity of the method through simulation of urban real-time traffic monitoring results.

Multi-Criteria, Graph-Based Road Centerline Vectorization Using Ordered Weighted Averaging Operators

In this paper a novel road vectorization methodology based on image space clustering technique and weighted graph theory is presented. The proposed methodology describes a road as a set of optimized points on the centerline which should be connected by defining a number of appropriate criteria. The main contribution of this paper is to design a weighting scheme for combining a small number of road identities using Ordered Weighted Averaging (owa) operators by defining appropriate decision strategy. In this regard, a novel geometric criterion is introduced. Result of the OWA aggregation specifies weight of each edge in the road network graph. Comparing the proposed approach with two state-of-the-art image space clustering-based road vectorization methods proves its efficiency to deal with roads with different widths, parallel roads with different distances, different types of intersections, and also noise clusters. Obtaining improved quality measures for several high-resolution images, demonstrates the successfulness of the vectorization approach.

Crossing behaviors of optical resonance modes in metallic metamaterials

We investigated the behavior of waveguide resonance modes in a metamaterial consisting of metallic slit-array slabs separated by an air gap. Simulation results show two unusual types of intersection phenomena. One type is an anticrossing with a specifically recognizable mode repulsion. An effective medium theory analysis revealed that this phenomenon can be explained in terms of an increased effective refractive index in the air-gap region. The other type of intersection leads to transmission suppression by the mixing of symmetric and asymmetric modes. This fade-out phenomenon is associated with a change in the behavior of the symmetric mode above a critical frequency.