Partially-commutative context-free languages

The paper is about a class of languages that extends context-free languages (CFL) and is stable under shuffle. Specifically, we investigate the class of partially-commutative context-free languages (PCCFL), where non-terminal symbols are commutative according to a binary independence relation, very much like in trace theory. The class has been recently proposed as a robust class subsuming CFL and commutative CFL. This paper surveys properties of PCCFL. We identify a natural corresponding automaton model: stateless multi-pushdown automata. We show stability of the class under natural operations, including homomorphic images and shuffle. Finally, we relate expressiveness of PCCFL to two other relevant classes: CFL extended with shuffle and trace-closures of CFL. Among technical contributions of the paper are pumping lemmas, as an elegant completion of known pumping properties of regular languages, CFL and commutative CFL.Comment: In Proceedings EXPRESS/SOS 2012, arXiv:1208.244

Розрахунок довговічності матеріалів при нерегулярному непропорційному навантажуванні

Із метою розробки адекватних моделей для розрахунку довговічності аналізуються наведені в літературних джерелах експериментальні дані щодо малоциклової втоми сталі 304 та титанового сплаву ВТ9 під час деформування за складними історіями навантаження, що являють собою у просторі повних деформацій послідовність блоків різних за формою циклів. За базові використовуються чотири моделі накопичування пошкоджень та деформаційний критерій малоциклової втоми. Виконано порівняльний аналіз моделей прогнозування довговічності. Показано, що застосування удосконаленого нелінійного правила накопичування пошкоджень дозволяє покращити результати прогнозування довговічності, причому у більшій мірі для програм, що включають непропорційні цикли.С целью разработки адекватных моделей для расчета долговечности анализируются приведенные в литературных источниках данные по малоцикловой усталости стали 304 и титанового сплава ВТ9 в процессе деформирования по сложным историям нагружения, которые представляют собой в пространстве полных деформаций последовательность блоков разных по форме циклов. В качестве базовых применяются четыре модели накопления повреждений и деформационный критерий малоцикловой усталости. Проведен сравнительный анализ моделей прогнозирования долговечности. Показано, что применение усовершенствованного нелинейного правила накопления повреждений позволяет улучшить результаты прогнозирования долговечности, причем в большей степени для программ, которые включают непропорциональные циклы.We analyze the experimental data available in the literature on low-cycle fatigue of 304 steel and VT9 titanium alloy subjected to loads with complex loading histories, which are represented in the space of total deformations by a sequence of loading blocks consisting of cycles of various shapes. As models for the material life prediction, we use four models of damage accumulation, as well as the low-cycle fatigue deformation criterion. A comparative analysis of life prediction models is provided. It is shown that application of the refined nonlinear damage accumulation rule leads to the improvement of the life prediction results, which effect is more pronounced for loading programs containing nonproportional cycles

Successful new product development by optimizing development process effectiveness in highly regulated sectors: the case of the Spanish medical devices sector

Rapid development and commercialization of new products is of vital importance for small and medium sized enterprises (SME) in regulated sectors. Due to strict regulations, competitive advantage can hardly be achieved through the effectiveness of product concepts only. If an SME in a highly regulated sector wants to excell in new product development (NPD) performance, the company should focus on the flexibility, speed, and productivity of its NPD function: i.e. the development process effectiveness. Our main research goals are first to explore if SMEs should focus on their their development process effectiveness rather than on their product concept effectiveness to achieve high NPD performance; and second, to explore whether a shared pattern in the organization of the NPD function can be recognized to affect NPD performance positively. The medical devices sector in Spain is used as an example of a\ud highly regulated sector. A structured survey among 11 SMEs, of which 2 were studied also as in in-depth case studies, led to the following results. First of all, indeed the companies in the dataset which focused on the effectiveness of their development process, stood out in NPD performance. Further, the higher performing companies did have a number of commonalities in the organisation of their NPD function: 1) The majority of the higher performing firms had an NPD strategy characterized by a predominantly incremental project portfolio.\ud 2) a) Successful firms with an incremental project portfolio combined this with a functional team structure b) Successful firms with a radical project portfolio combined this with a heavyweight or autonomous team structure.\ud 3) A negative reciprocal relationship exists between formalization of the NPD processes and the climate of the NPD function, in that a formalized NPD process and an innovative climate do not seem to reinforce each other. Innovative climate combined with an informal NPD process does however contribute positively to NPD performance. This effect was stronger in combination with a radical project portfolio. The highest NPD performance was measured for companies focusing mainly on incremental innovation. It is argued that in highly regulated sectors, companies with an incremental product portfolio would benefit from employing a functional structure. Those companies who choose for a more radical project portfolio in highly regulated sectors should be aware\ud that they are likely to excell only in the longer term by focusing on strategic flexibility. In their NPD organization, they might be well advised to combine informal innovation processes with an innovative climate

Specific character of citations in historiography (using the example of Polish history)

The first part of the paper deals with the assessment of international databases in relation to the number of historical publications (representation and relevance in comparison with the model database). The second part is focused on providing answer to the question whether historiography is governed by similar bibliometric rules as exact sciences or whether it has its own specific character. Empirical database for this part of the research constituted the database prepared ad hoc: The Citation Index of the History of Polish Media (CIHPM). Among numerous typically historical features the main focus was put on: linguistic localism, specific character of publishing forms, differences in citing of various sources (contributions and syntheses) and specific character of the authorship (the Lorenz Curve and the Lotka’s Law). Slightly more attention was devoted to the half-life indicator and its role in a diachronic study of a scientific field; also, a new indicator (HL14), depicting distribution of citations younger then half-life was introduced. Additionally, the comparison and correlation of selected parameters for the body of historical science (citations, HL14, the Hirsch Index, number of publications, volume and other) were also conducted

Temperament in preadolescence is associated with weight and eating pathology in young adulthood

Objective Few longitudinal studies have investigated the role of temperament traits on weight and eating problems thus far. We investigated whether temperament in preadolescence influences body weight and the development of eating pathology in adolescence and young adulthood. Method This study used data from TRAILS (Tracking Adolescents' Individual Lives Survey), a Dutch community cohort study (N = 2,230) from preadolescence into adulthood. At age 11, the temperament dimensions negative affectivity and effortful control were measured with the Early Adolescent Temperament Questionnaire-Revised. Body mass index (BMI) was measured at all assessment waves. At age 19, the prevalence of eating disorders was investigated by two-stage screening including interviews by eating disorder experts. At age 22 and 26, the Eating Disorder Diagnostic Scale was used to assess the level of eating pathology. Results Higher negative affectivity in preadolescence was associated with higher BMI and eating pathology in young adulthood. Lower effortful control in preadolescence was found to be a risk factor for the development of obesity in young adulthood. No association was found between effortful control in preadolescence and eating pathology in later life. Discussion Both negative affectivity and effortful control play a role in the development of weight or eating problems during adolescence

Chronic Stress and Adolescents' Mental Health:Modifying Effects of Basal Cortisol and Parental Psychiatric History. The TRAILS Study

Large individual differences in adolescent mental health following chronic psychosocial stress suggest moderating factors. We examined two established moderators, basal cortisol and parental psychiatric history, simultaneously. We hypothesized that individuals with high basal cortisol, assumed to indicate high context sensitivity, would show relatively high problem levels following chronic stress, especially in the presence of parental psychiatric history. With Linear Mixed Models, we investigated the hypotheses in 1917 Dutch adolescents (53.2 % boys), assessed at ages 11, 13.5, and 16. Low basal cortisol combined with the absence of a parental psychiatric history increased the risk of externalizing but not internalizing problems following chronic stress. Conversely, low basal cortisol combined with a substantial parental psychiatric history increased the risk of internalizing but not externalizing problems following chronic stress. Thus, parental psychiatric history moderated stress- cortisol interactions in predicting psychopathology, but in a different direction than hypothesized. We conclude that the premise that basal cortisol indicates context sensitivity may be too crude. Context sensitivity may not be a general trait but may depend on the nature of the context (e.g., type or duration of stress exposure) and on the outcome of interest (e.g., internalizing vs. externalizing problems). Although consistent across informants, our findings need replication