arXiv subjects

Daisuke Ishii

Publications and source records attributed to Daisuke Ishii.

At least 19 recordsLinked to original sources

arXiv2026

Pulling Illusion in Individuals with Neurological Disorders

The pulling illusion induced by asymmetric vibration stimuli has attracted attention for its potential applications in rehabilitation and sensory assessment. However, the underlying mechanism of the pulling illusion remains unclear. This study addressed the central question of whether peripheral vibrotactile sensitivity alone is sufficient for the illusion to emerge or whether processing beyond basic vibration detection is also required. Neurological disorders can involve impairments at different levels of the nervous system, providing an opportunity to examine this question. Accordingly, we evaluated directional discrimination performance for the pulling illusion and fingertip vibration detection thresholds in 25 participants with diverse neurological disorders affecting different levels of the nervous system, from peripheral to central. Clustering analysis identified contrasting profiles, with high directional discrimination performance despite elevated vibration detection thresholds and chance-level performance despite relatively low-to-intermediate thresholds. In the generalized linear mixed model, motor-related signs, including hemiplegia and tremor, showed a robust negative association with directional discrimination performance, whereas vibration detection threshold was not robustly associated with performance. Furthermore, in participants with hemiplegia, directional discrimination performance was around chance level on the affected side and close to 100% on the unaffected side, despite stimulus amplitudes well above the measured vibration detection thresholds on both sides. Collectively, these findings suggest that the pulling illusion depends on perceptual processing beyond basic vibration detection, through which asymmetric vibration is experienced as directional pulling.

q-bio.NC↗

arXiv2026

Canonical Lattices of Integer Relations Associated to Rational Fans: Wall Generation and a Two-Step Support Filtration

We study the lattice $L_{\mathrm{rel}}(Σ)=\ker\big(\mathbb{Z}^{Σ(1)}\to N\big)$ of integer relations among the primitive ray generators of a rational fan $Σ$, from an intrinsic, coordinate-free point of view. For each cone $τ\inΣ$ we introduce the \emph{star-supported} sublattice $L_{\mathrm{rel}}(\operatorname{Star}(τ))$ of relations whose support lies in the star of $τ$, and we organize these by codimension into a support filtration $F_\bullet L_{\mathrm{rel}}(Σ)$. Our main result is a sharp local generation theorem: for a complete fan the relation lattice is generated \emph{integrally} by the relations supported on the stars of walls (codimension-one cones). Equivalently, the support filtration collapses after a single step, $F_1 L_{\mathrm{rel}}(Σ)=L_{\mathrm{rel}}(Σ)$. This is an intrinsic repackaging of the classical wall (wall-crossing) relations that generate the group of numerically trivial classes on a complete toric variety. We make the resulting two-step structure precise: for simplicial fans one has $0=F_0\subsetneq F_1=L_{\mathrm{rel}}(Σ)$, while for general fans $F_0$ records the intrinsic relations of non-simplicial maximal cones and $F_1$ adds exactly the wall relations. We prove functoriality of $L_{\mathrm{rays}}$ and $L_{\mathrm{rel}}$ under fan isomorphisms and ray-preserving subdivisions, deduce that every primitive collection of size $m$ is wall-generated, and illustrate the theory on $\mathbb{P}^2\times\mathbb{P}^1$, products of projective lines, weighted projective spaces, and the (non-simplicial) fan over a cube. We are careful throughout to distinguish what the filtration does and does not detect, correcting a natural but false expectation that support-codimension yields a strictly increasing multi-step invariant.

math.CO↗

arXiv2026

Combinatorial Cycle Classes in the Intersection Cohomology of Projective Toric Varieties

We investigate cycle-class realizations inside the combinatorial intersection cohomology for fans developed by Barthel, Brasselet, Fieseler, and Kaup (BBFK). For projective toric varieties, the intersection cohomology is Hodge-Tate, and thus the space of rational Hodge classes coincides with the full rational even-degree intersection cohomology. We formulate a compatibility statement between combinatorial and geometric cycle classes and explore it in the torus-invariant setting under standard functoriality assumptions. The central question we address is whether these invariant combinatorial cycle classes span the even-degree combinatorial intersection cohomology $IH^{2k}_{\mathrm{comb}}(Σ, \mathbb{Q})$. Assuming the stated BBFK--BL compatibility, we verify this linear-generation statement for projective toric varieties of dimension at most $3$; the simplicial case follows unconditionally from standard rational cohomology descriptions. We illustrate the framework with a non-simplicial example in dimension $3$ for which the Betti numbers and spanning property are derived directly from Stanley's toric $h$-vector formula and Fieseler's surjectivity theorem.

math.AG↗

arXiv2026

Bit-Precise Conformance Testing of Simulink Model Checkers

MATLAB/Simulink provides a practical modeling language and a simulation engine for the development of cyber-physical systems. To ensure the quality of the developed models, there are formal verification tools available, such as Simulink Design Verifier (SLDV) and third-party SMT-based model checkers (SmtMC). However, due to the absence of a semantics of Simulink that covers every element of models and the details of its numerical behavior, the reliability of the model checkers themselves is often doubtful, potentially analyzing models differently from the simulator. This work aims to verify the quality of the Simulink model checkers by addressing the following items. 1) Formalization of the basic block types of Simulink. It involves defining block type feature sets and the bit-precise behavior of the blocks. 2) A method for testing bit-precise conformance relations among the tools for each block type. The pass rate of our test suite measures (i) conformance of model checking results with simulation results by Simulink and (ii) conformance between the results of SmtMC and SLDV. 3) Experiment to perform tests on 10 block types. We confirmed that SmtMC efficiently passed all test cases, while SLDV achieved pass rates of only 94-96% and 80-90% for conformance (i) and (ii), respectively. We analyzed the causes of failed tests, such as errors, corner cases, and timeouts.

cs.SE↗

arXiv2026

The Accessibility Capability Boundary: Operational Limits and Expansion Potential of AI-Generated Browser-Native Accessibility Systems

As large language models (LLMs) demonstrate increasing competence in synthesizing functional user interfaces, a fundamental question emerges in accessibility computing: \textit{how far can AI-driven accessibility systems go?} This paper introduces the \textit{Accessibility Capability Boundary} (ACB), a formal framework for reasoning about the operational limits and expansion potential of autonomous accessibility systems, and grounds this theory in a real-world systems artifact. We model accessibility not as a binary compliance property but as a dynamic, multidimensional capability space constrained by measurable variables including deployment latency, cognitive load, infrastructure dependency, offline persistence, interaction complexity, and adaptability. We argue that AI-generated, browser-native systems constructed as single-file HTML artifacts leveraging standard browser APIs may dramatically shift the ACB outward by reducing deployment friction to near-zero and enabling rapid, context-specific interface adaptation. We ground our theoretical framework in the analysis of two real-world exploratory prototypes. The first is an AI-generated browser-native accessibility interface deployed for a blind user in Nepal. The second is a fully functional, open-source webcam alignment assistant for visually impaired users, serving as a concrete systems artifact. Through formal definitions, propositions, and a comparative evaluation matrix, we characterize the regions of the accessibility capability space that such systems can and cannot reach. We further identify remaining computational, infrastructural, and verification constraints that constitute the hard boundaries of this paradigm. This work contributes a theoretical foundation for understanding the scalable limits of autonomous accessibility computing and proposes a research agenda for future work in accessibility-aware AI systems.

cs.HC↗

arXiv2026

Explainable PQC: A Layered Interpretive Framework for Post-Quantum Cryptographic Security Assumptions

This paper studies how post-quantum cryptographic (PQC) security assumptions can be represented and communicated through a structured, layered framework that is useful for technical interpretation but does not replace formal cryptographic proofs. We propose ``Explainable PQC,'' an interdisciplinary framework connecting three layers: (1) a complexity-based interpretive model that distinguishes classical security, quantum security, and reduction-backed hardness, drawing on computational complexity classes as supporting language; (2) an exploratory mathematical investigation applying combinatorial Hodge theory and polyhedral geometry to study structural aspects of lattice hardness; and (3)~an empirical experimentation platform, implemented in Julia, for measuring the behavior of lattice basis reduction algorithms (LLL, BKZ) in low-dimensional settings. The motivating case study throughout the paper is lattice-based PQC, including ML-KEM (FIPS 203) and ML-DSA (FIPS 204). The contribution of this paper is conceptual and organizational: it defines a layered interpretive framework, clarifies its scope relative to formal cryptographic proofs and reduction-based security arguments, and identifies mathematical and implementation-level directions through which PQC security claims may be more transparently communicated. This paper does not claim new cryptographic hardness results, new attacks, or concrete security parameter estimates.

cs.CR↗

arXiv2025

Comparison of Lightweight Methods for Vehicle Dynamics-Based Driver Drowsiness Detection

Driver drowsiness detection (DDD) prevents road accidents caused by driver fatigue. Vehicle dynamics-based DDD has been proposed as a method that is both economical and high performance. However, there are concerns about the reliability of performance metrics and the reproducibility of many of the existing methods. For instance, some previous studies seem to have a data leakage issue among training and test datasets, and many do not openly provide the datasets they used. To this end, this paper aims to compare the performance of representative vehicle dynamics-based DDD methods under a transparent and fair framework that uses a public dataset. We first develop a framework for extracting features from an open dataset by Aygun et al. and performing DDD with lightweight ML models; the framework is carefully designed to support a variety of onfigurations. Second, we implement three existing representative methods and a concise random forest (RF)-based method in the framework. Finally, we report the results of experiments to verify the reproducibility and clarify the performance of DDD based on common metrics. Among the evaluated methods, the RF-based method achieved the highest accuracy of 88 %. Our findings imply the issues inherent in DDD methods developed in a non-standard manner, and demonstrate a high performance method implemented appropriately.

cs.LG↗

arXiv2024

Tensegrity-Inspired Polymer Films: Progressive Bending Stiffness through Multipolymeric Patterning

Materials with J-shaped stress-strain behavior under uniaxial stretching, where strength increases as deformation progresses, have been developed through various materials designs. On the other hand, polymer materials that progressively stiffen under bending remain unrealized. To address this gap, this study drew inspiration from membrane tensegrity structures, which achieve structural stability by balancing compressive forces in rods and tensile forces in membrane. Notably, some of these structures exhibit increased stiffness under bending. Using a multipolymer patterning technique, we developed a polymer film exhibiting membrane tensegrity-like properties that stiffens under bending. This effect results from membrane tension generated by rod protrusions and an increase in second moment of area at regions with maximum curvature.

cond-mat.soft↗

arXiv2024

A Hypergraph-based Formalization of Hierarchical Reactive Modules and a Compositional Verification Method

The compositional approach is important for reasoning about large and complex systems. In this work, we address synchronous systems with hierarchical structures, which are often used to model cyber-physical systems. We revisit the theory of reactive modules and reformulate it based on hypergraphs to clarify the parallel composition and the hierarchical description of modules. Then, we propose an automatic verification method for hierarchical systems. Given a system description annotated with assume-guarantee contracts, the proposed method divides the system into modules and verifies them separately to show that the top-level system satisfies its contract. Our method allows an input to be a circular system in which submodules mutually depend on each other. Experimental result shows our method can be effectively implemented using an SMT-based model checker.

cs.SE↗

arXiv2022

SMT-Based Model Checking of Industrial Simulink Models

The development of embedded systems requires formal analysis of models such as those described with MATLAB/Simulink. However, the increasing complexity of industrial models makes analysis difficult. This paper proposes a model checking method for Simulink models using SMT solvers. The proposed method aims at (1) automated, efficient and comprehensible verification of complex models, (2) numerically accurate analysis of models, and (3) demonstrating the analysis of Simulink models using an SMT solver (we use Z3). It first encodes a target model into a predicate logic formula in the domain of mathematical arithmetic and bit vectors. We explore how to encode various Simulink blocks exactly. Then, the method verifies a given invariance property using the k-induction-based algorithm that extracts a subsystem involving the target block and unrolls the execution paths incrementally. In the experiment, we applied the proposed method and other tools to a set of models and properties. Our method successfully verified most of the properties including those unverified with other tools.

cs.LO↗

arXiv2022

Formalizing the Soundness of the Encoding Methods of SAT-based Model Checking

One of the effective model checking methods is to utilize the efficient decision procedure of SAT (or SMT) solvers. In a SAT-based model checking, a system and its property are encoded into a set of logic formulas and the safety is checked based on the satisfiability of the formulas. As the encoding methods are improved and crafted (e.g., k-induction and IC3/PDR), verifying their correctness becomes more important. This research aims at a formal verification of the SMC methods using the Coq proof assistant. Our contributions are twofold: (1) We specify the basic encoding methods, k-induction and (a simplified version of) IC3/PDR in Coq as a set of simple and modular encoding predicates. (2) We provide a formal proof of the soundness of the encoding methods based on our formalized lemmas on state sequences and paths.

cs.LO↗

arXiv2021

Compositional Test Generation of Industrial Synchronous Systems

Synchronous systems provide a basic model of embedded systems and industrial systems are modeled as Simulink diagrams and/or Lustre programs. Although the test generation problem is critical in the development of safe systems, it often fails because of the spatial and temporal complexity of the system descriptions. This paper presents a compositional test generation method to address the complexity issue. We regard a test case as a counterexample in safety verification, and represent a test generation process as a deductive proof tree built with dedicated inference rules; we conduct both spatial- and temporal-compositional reasoning along with a modular system structure. A proof tree is generated using our semi-automated scheme involving manual effort on contract generation and automatic processes for counterexample search with SMT solvers. As case studies, the proposed method is applied to four industrial examples involving such features as enabled/triggered subsystems, multiple execution rates, filter components, and nested counters. In the experiments, we successfully generated test cases for target systems that were difficult to deal with using the existing tools.

cs.SE↗

arXiv2021

Approximate Translation from Floating-Point to Real-Interval Arithmetic

Floating-point arithmetic (FPA) is a mechanical representation of real arithmetic (RA), where each operation is replaced with a rounded counterpart. Various numerical properties can be verified by using SMT solvers that support the logic of FPA. However, the scalability of the solving process remains limited when compared to RA. In this paper, we present a decision procedure for FPA that takes advantage of the efficiency of RA solving. The proposed method abstracts FP numbers as rational intervals and FPA expressions as interval arithmetic (IA) expressions; then, we solve IA formulas to check the satisfiability of an FPA formula using an off-the-shelf RA solver (we use CVC4 and Z3). In exchange for the efficiency gained by abstraction, the solving process becomes quasi-complete; we allow to output unknown when the satisfiability is affected by possible numerical errors. Furthermore, our IA is meticulously formalized to handle the special value NaN. We implemented the proposed method and compared it to four existing SMT solvers in the experiments. As a result, we confirmed that our solver was efficient for instances where rounding modes were parameterized.

cs.LO↗

arXiv2020

Computer-Assisted Verification of Four Interval Arithmetic Operators

Interval arithmetic libraries provide the four elementary arithmetic operators for operand intervals bounded by floating-point numbers. Actual implementations need to make a large case analysis that considers, e.g., magnitude relations between all pairs of argument bounds, positional relations between the arguments and zero, and handling of the special values, infinities and NaN. Their correctness is not obvious as they are implemented by human hands, which comes to be critical for the reliability. This work provides a mechanically-verified interval arithmetic library. For this purpose, we utilize the Why3 platform equipped with a specification language for annotated programs and back-end theorem provers. We conduct several proof tasks for each of three properties of the target code: validity, soundness, and tightness; zero division exception handling is also verified for the division code. To accomplish the proof, we propose several techniques for specification/verification. First, we specify additional lemmas that support deductions made by back-end SMT solvers, which enable to discharge proof obligations in floating-point arithmetic containing nonlinear terms. Second, we examine the annotation of tightness, which requires to assume that a computation may result in NaN; we propose specific extremum operators for this purpose. In the experiments, applying the techniques in conjunction with the Alt-Ergo SMT solver and the Coq proof assistant proved the entire code.

cs.LO↗

arXiv2019

Declarative Semantics of the Hybrid Constraint Language HydLa

Hybrid systems are dynamical systems with continuous evolution of states and discrete evolution of states and governing equations. We have worked on the design and implementation of HydLa, a constraint-based modeling language for hybrid systems, with a view to the proper handling of uncertainties and the integration of simulation and verification. HydLa's constraint hierarchies facilitate the description of constraints with adequate strength, but its semantical foundations are not obvious due to the interaction of various language constructs. This paper gives the declarative semantics of HydLa and discusses its properties and consequences by means of examples.

cs.PL↗

arXiv2017

HySIA: Tool for Simulating and Monitoring Hybrid Automata Based on Interval Analysis

We present HySIA: a reliable runtime verification tool for nonlinear hybrid automata (HA) and signal temporal logic (STL) properties. HySIA simulates an HA with interval analysis techniques so that a trajectory is enclosed sharply within a set of intervals. Then, HySIA computes whether the simulated trajectory satisfies a given STL property; the computation is performed again with interval analysis to achieve reliability. Simulation and verification using HySIA are demonstrated through several example HA and STL formulas.

cs.LO↗

arXiv2016

Monitoring Temporal Properties using Interval Analysis

Verification of temporal logic properties plays a crucial role in proving the desired behaviors of continuous systems. In this paper, we propose an interval method that verifies the properties described by a bounded signal temporal logic. We relax the problem so that if the verification process cannot succeed at the prescribed precision, it outputs an inconclusive result. The problem is solved by an efficient and rigorous monitoring algorithm. This algorithm performs a forward simulation of a continuous-time dynamical system, detects a set of time intervals in which the atomic propositions hold, and validates the property by propagating the time intervals. In each step, the continuous state at a certain time is enclosed by an interval vector that is proven to contain a unique solution. We experimentally demonstrate the utility of the proposed method in formal analysis of nonlinear and complex continuous systems.

cs.LO↗

arXiv2015

Monitoring Bounded LTL Properties Using Interval Analysis

Verification of temporal logic properties plays a crucial role in proving the desired behaviors of hybrid systems. In this paper, we propose an interval method for verifying the properties described by a bounded linear temporal logic. We relax the problem to allow outputting an inconclusive result when verification process cannot succeed with a prescribed precision, and present an efficient and rigorous monitoring algorithm that demonstrates that the problem is decidable. This algorithm performs a forward simulation of a hybrid automaton, detects a set of time intervals in which the atomic propositions hold, and validates the property by propagating the time intervals. A continuous state at a certain time computed in each step is enclosed by an interval vector that is proven to contain a unique solution. In the experiments, we show that the proposed method provides a useful tool for formal analysis of nonlinear and complex hybrid systems.

cs.LO↗