96 research outputs found
The Reachability Problem for Petri Nets is Not Elementary
Petri nets, also known as vector addition systems, are a long established
model of concurrency with extensive applications in modelling and analysis of
hardware, software and database systems, as well as chemical, biological and
business processes. The central algorithmic problem for Petri nets is
reachability: whether from the given initial configuration there exists a
sequence of valid execution steps that reaches the given final configuration.
The complexity of the problem has remained unsettled since the 1960s, and it is
one of the most prominent open questions in the theory of verification.
Decidability was proved by Mayr in his seminal STOC 1981 work, and the
currently best published upper bound is non-primitive recursive Ackermannian of
Leroux and Schmitz from LICS 2019. We establish a non-elementary lower bound,
i.e. that the reachability problem needs a tower of exponentials of time and
space. Until this work, the best lower bound has been exponential space, due to
Lipton in 1976. The new lower bound is a major breakthrough for several
reasons. Firstly, it shows that the reachability problem is much harder than
the coverability (i.e., state reachability) problem, which is also ubiquitous
but has been known to be complete for exponential space since the late 1970s.
Secondly, it implies that a plethora of problems from formal languages, logic,
concurrent systems, process calculi and other areas, that are known to admit
reductions from the Petri nets reachability problem, are also not elementary.
Thirdly, it makes obsolete the currently best lower bounds for the reachability
problems for two key extensions of Petri nets: with branching and with a
pushdown stack.Comment: Final version of STOC'1
The reachability problem for Petri nets is not elementary
Petri nets, also known as vector addition systems, are a long established model of concurrency with extensive applications in modelling and analysis of hardware, software and database systems, as well as chemical, biological and business processes. The central algorithmic problem for Petri nets is reachability: whether from the given initial configuration there exists a sequence of valid execution steps that reaches the given final configuration. The complexity of the problem has remained unsettled since the 1960s, and it is one of the most prominent open questions in the theory of verification. Decidability was proved by Mayr in his seminal STOC 1981 work, and the currently best published upper bound is non-primitive recursive Ackermannian of Leroux and Schmitz from LICS 2019. We establish a non-elementary lower bound, i.e. that the reachability problem needs a tower of exponentials of time and space. Until this work, the best lower bound has been exponential space, due to Lipton in 1976. The new lower bound is a major breakthrough for several reasons. Firstly, it shows that the reachability problem is much harder than the coverability (i.e., state reachability) problem, which is also ubiquitous but has been known to be complete for exponential space since the late 1970s. Secondly, it implies that a plethora of problems from formal languages, logic, concurrent systems, process calculi and other areas, that are known to admit reductions from the Petri nets reachability problem, are also not elementary. Thirdly, it makes obsolete the currently best lower bounds for the reachability problems for two key extensions of Petri nets: with branching and with a pushdown stack
コミュニケーションが関係維持に及ぼす影響についての友人関係機能の仲介効果
本研究は,普段からよく会う友人関係(High Interaction : HI友人関係)とめったに会えないが親密な友人関係(Low Interaction : LI友人関係)の2種類の友人関係を対象に以下に述べるような検討を実施した。それは,コミュニケーションの内容(古谷・坂田,2006) と友人関係満足度の関連における友人関係機能 (丹野・松井, 2006) の仲介効果の検討である。分析の結果, LI友人では課題的,情緒的コミュニケーションが関係性評価を仲介し,関係満足度に正の 影響を与えていた。HI友人では情緒的,コンサマトリー的コミュニケーションが関係性評価を仲介し,関係満足度に正の影響を与えていた
Effects of SO2 on respiratory system of adult Miyakejima resident 2 years after returning to the island.
BACKGROUND: Mt. Oyama in Miyakejima Island erupted in June, 2000. All Miyake villagers were forced to evacuate from the island in September, 2000, due to continuous eruptions and emissions of unsafe amounts of volcanic gas, mainly SO2. From February, 2005, Miyake villagers returned to the island despite volcanic gas still being emitted. OBJECTIVES: This study examines the 2-yr changes in Miyake residents' respiratory systems from autumn 2004 to November 2006. METHODS: The study population was 823 Miyake adult residents who participated in the health check-up in 2006. Respiratory effects were evaluated by a questionnaire for respiratory symptoms and spirometry. SO2 has been continuously monitored at 7 sampling points of the inhabited area. The mean SO2 concentration from February 2005 to November 2006 was 0.031 ppm. The area was categorized into 4 areas by SO2 concentration, namely, areas L, H-1, H-2 and H-3, where average SO2 concentrations were 0.019, 0.026, 0.032, and 0.045 ppm, respectively. RESULTS: The study subjects showed no deterioration in lung function. Prevalence of cough and phlegm among all participants were significantly higher in 2006 than in 2004, and age-, sex- and smoking-adjusted odds ratios of cough and phlegm were 1.75 (95%CI 1.33-2.30) and 1.44 (1.12-1.87). Prevalence of chronic bronchitis-like symptoms among normosusceptive subjects in 2006 was 4.1% which was significantly higher than that of 2.1% in 2004 (p=0.035). Compared to area L, the frequencies of phlegm and irritation of the nose were significantly increased in areas H-2 and H-3. CONCLUSION: SO2 exposure-related respiratory symptoms were observed in adult Miyakejima residents after returning to the island
Facilitating the First Move: Exploring Inspirational Design Patterns for Aiding Initiation of Social Encounters
BGWM as Second Constituent of Complex Matrix Model
Earlier we explained that partition functions of various matrix models can be
constructed from that of the cubic Kontsevich model, which, therefore, becomes
a basic elementary building block in "M-theory" of matrix models. However, the
less topical complex matrix model appeared to be an exception: its
decomposition involved not only the Kontsevich tau-function but also another
constituent, which we now identify as the Brezin-Gross-Witten (BGW) partition
function. The BGW tau-function can be represented either as a generating
function of all unitary-matrix integrals or as a Kontsevich-Penner model with
potential 1/X (instead of X^3 in the cubic Kontsevich model).Comment: 42 page
長期入院中統合失調症患者における抗精神病薬・抗コリン薬慢性投与の認知機能・症状・生活の質に及ぼす影響
長期入院中統合失調症患者における抗精神病薬及び抗コリン薬の慢性投与が認知機能・症状・生活の質に及ぼす影響を検討するため,各評価尺度と抗精神病薬haloperidol(HPD)換算量及び抗コリン薬biperiden(BPD)換算量との関連性を検討した。各評価尺度として,Hasegawa Dementia Scale-Revised(HDS-R),Brief Psychiatric Rating Scale(BPRS),The Schizophrenia Quality of Life Scale, a Japanese version(JSQLS)を用いた。定型抗精神病薬(定型薬)のみ処方群と非定型抗精神病薬(非定型薬)のみ処方群の間でのBPRS下位項目(陽性症状,陰性症状,気分変調,躁症状)得点における有意差,定型薬HPD換算量・抗コリン薬BPD換算量のJSQLS下位項目(心理社会関係の障害,動機・活力の低下)に対する相関性が認められた。以上から,精神症状遷延化症例において,定型薬処方継続の傾向が示唆され,加えて定型薬及び抗コリン薬投与の固定化は,慢性期の統合失調症患者に対し自立や社会復帰において負の影響を与える可能性が高いことが示唆された。We examined the effects of chronic treatments using antipsychotics and cholinergic agents for long-stay schizophrenic inpatients with reference to their cognitive functions, psychiatric symptoms, and their quality of life. Hasegawa Dementia Scale-Revised (HDS-R), Brief Psychiatric Rating Scale (BPRS), The Schizophrenia Quality of Life Scale, and a Japanese version (JSQLS) were used as each measure for evaluation of their cognitive functions, psychiatric symptoms, and their quality of life. In addition, we examined the correlation between amount of antipsychotics or anticholinergic agents per one patient and each measure for the above-mentioned evaluation. The results showed that there was a significant correlation between amount of typical antipsychotics or anticholinergic agents and quality of life. Furthermore, there was significant difference in BPRS score between patients administered typical antipsychotics and patients administered atypical antipsychotics. In conclusion, the results suggest the tendency to continue the same prescription of typical antipsychotic in the patients whose symptoms do not improve easily. In addition, the results suggest that long-term administration of typical antipsychotics and anticholinergic agents has a negative influence on independence and rehabilitation into society in patients with schizophrenia of the chronic phase.原著Original Article
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