Combining ergonomics, culture and scenario for the design of a cooperation platform

Analyzing the way computer technologies are used is crucial for their development. Such analyses make it possible to evaluate these technologies and enhance their evolution. The present article presents some ideas drawn from the development of a cooperation platform for elementary school children (10–11 years old). On the basis of an obvious ergonomic requirement, we worked on two other dimensions: cultural aspects and the teaching scenario. The goal was to set up observation situations and analyze the conversations produced during those situations, in order to understand what using the platform meant to both the pupils and their teachers.

Cynipid gall-wasp communities correlate with oak chemistry

Host-plant association data, gathered from field surveys conducted throughout Florida and from the literature, were used to identify the specificity of cynipid gall inducers to one or more of six Quercus species that occur at Archbold Biological Station, Lake Placid, Florida, USA, including the red oaks Q. laevis, Q. myrtifolia, and Q. inopina, and the white oaks Q. chapmanii, Q. geminata, and Q. minima. Quercus myrtifolia had the highest cynipid richness and diversity (37 cynipid species, Shannon H = 3.61, Simpson's D = 0.97), followed by Q. chapmanii, Q. laevis, Q. inopina, Q. geminata, and finally Q. minima (10 species, H = 2.30, D = 0.90). All cynipid species showed strong fidelity to a particular host plant or a restricted set of host plants. An ordination of gall-wasp host associations indicated that the cynipid communities of each oak species were distinct and specific to a given oak species. Leaf samples taken from each oak species were analyzed for condensed and hydrolyzable tannins, total phenolics, lignin, cellulose and hemicellulose, nitrogen, and carbon. All of these chemical traits, with the exception of carbon, differed by oak species, and the differences were strongly correlated with the axes of the cynipid--species ordination. These results suggest that gall-wasp occurrence is influenced by oak chemistry and imply that experimental studies of cynipid gall inducers that examine host-plant chemistry and female oviposition choice and larval performance will yield useful insights.     

Fault prediction and the discriminative powers of connectivity-based object-oriented class cohesion metrics

Context

Several metrics have been proposed to measure the extent to which class members are related. Connectivity-based class cohesion metrics measure the degree of connectivity among the class members.

Objective

We propose a new class cohesion metric that has higher discriminative power than any of the existing cohesion metrics. In addition, we empirically compare the connectivity and non-connectivity-based cohesion metrics.

Method

The proposed class cohesion metric is based on counting the number of possible paths in a graph that represents the connectivity pattern of the class members. We theoretically and empirically validate this path connectivity class cohesion (PCCC) metric. The empirical validation compares seven connectivity-based metrics, including PCCC, and 11 non-connectivity-based metrics in terms of discriminative and fault detection powers. The discriminative-power study explores the probability that a cohesion metric will incorrectly determine classes to be cohesively equal when they have different connectivity patterns. The fault detection study investigates whether connectivity-based metrics, including PCCC, better explain the presence of faults from a statistical standpoint in comparison to other non-connectivity-based cohesion metrics, considered individually or in combination.

Results

The theoretical validation demonstrates that PCCC satisfies the key cohesion properties. The results of the empirical studies indicate that, in contrast to other connectivity-based cohesion metrics, PCCC is much better than any comparable cohesion metric in terms of its discriminative power. In addition, the results also indicate that PCCC measures cohesion aspects that are not captured by other metrics, wherein it is considerably better than other connectivity-based metrics but slightly worse than some other non-connectivity-based cohesion metrics in terms of its ability to predict faulty classes.

Conclusion

PCCC is more useful in practice for the applications in which practitioners need to distinguish between the quality of different classes or the quality of different implementations of the same class.     

基于一致性算法的多智能体系统能控性性质

针对多智能体系统能控性方面的问题,采用图论及矩阵的方法研究了多智能体系统在对称拓扑和多领航者情况下的能控性,给出了拓扑结构为对称的系统能控性的几个性质。在领航者为多个时,指出了不对称的拓扑结构不再是多智能体系统能控性的必要条件。证明结果表明,图中连通枝的对称性（不是整个图对称）将导致系统的不能控以及在领航者是多个的情况下,如果领航者是来自任意的单元素单元,那么系统是不能控的。该结果为分析基于一致性算法的多智能体能控性提供了新的启示。     

H-Solid State NMR Studies of Tunneling Phenomena and Isotope Effects in Transition Metal Dihydrides

In many transition metal dihydrides and dihydrogen complexes the hydrogens are relatively weakly bound and exhibit a fairly high mobility, in particular with respect to their mutual exchange. Part of this high mobility is due to the exchange symmetry of the two hydrogens, which causes an energy splitting into even and odd spatial energy eigenfunctions, resulting in the typical coherent tunneling of a two-level system. Owing to the quantum mechanical symmetry selection principles the eigenfunctions are connected to the possible nuclear spin states of the system. If the tunneling frequency is in the proper frequency window it is thus possible to observe these tunneling transitions by NMR at very low temperatures, where no thermally induced exchange reactions overshadow the tunneling. The first part of this review gives an introduction into the interplay of chemical kinetics and tunneling phenomena in general, rotational tunneling of dihydrogen in a two-fold potential in particular and the Bell tunnel model, followed by a summary of solid state NMR techniques for the observation of these tunnel processes. Then a discussion of the effects of these processes on the ²H NMR line shape is given. The second part of the review reports results of a ²H-solid state NMR spectroscopy and T₁ relaxatiometry study of trans-[Ru(D₂)Cl(PPh₂CH₂CH₂PPh₂)₂]PF₆, in the temperature regime from 5.4 to 320 K. In the Ru-D₂ sample coherent tunneling and incoherent exchange processes on the time scale of the quadrupolar interaction are observed. From the spectra and T₁-data the height of the tunneling barrier is determined. Next results of ²H-spin–lattice relaxation measurements for a selectively η² − D₂ labeled isotopomer of the complex W(PCy₃)₂(CO)₃)(η² − D₂) are presented and discussed. The relaxation measurements are analyzed in terms of a simple one dimensional Bell tunnel model and comparison to incoherent neutron scattering (INS) data from the H₂ complex. The comparison reveals a strong isotope effect of 2 × 10³ for the exchange rates of the deuterons versus hydrons.     

基于主动规则的多用户交互模型

论述了多用户交互的特性,提出了一个多用户交互模型(E*Fb*Ft)nCAn。针对该模型的特点,建立起ECA规则模型,讨论了交互事件、回调事件和复合事件。分析了将(E*Fb*Ft)nCAn模型转换为主动机制系统中的事件、规则的方法。用例表明基于主动机制的(E*Fb*Ft)nCAn模型是有效的。     

A Comparative Study of the Use of Visual Communicative Signals in Interactions Between Dogs (Canis familiaris) and Humans and Cats (Felis catus) and Humans.

Dogs' (Canis familiaris) and cats' (Felis catus) interspecific communicative behavior toward humans was investigated. In Experiment 1, the ability of dogs and cats to use human pointing gestures in an object-choice task was compared using 4 types of pointing cues differing in distance between the signaled object and the end of the fingertip and in visibility duration of the given signal. Using these gestures, both dogs and cats were able to find the hidden food; there was no significant difference in their performance. In Experiment 2, the hidden food was made inaccessible to the subjects to determine whether they could indicate the place of the hidden food to a naive owner. Cats lacked some components of attention-getting behavior compared with dogs. The results suggest that individual familiarization with pointing gestures ensures high-level performance in the presence of such gestures; however, species-specific differences could cause differences in signaling toward the human. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Teachers' and Pupils' Behavior in Large and Small Classes: A Systematic Observation Study of Pupils Aged 10 and 11 Years.

The authors examined class size effects on teacher-pupil interactions, pupil engagement, and pupil-pupil interaction. They extended previous research by recognizing the hierarchical nature of observation data and the possible influence of other variables. The study used a time sampling method involving 257 children (aged 10-11 years) in 16 small (25 or under) and 26 large (31 and over) classes. In small classes, there were more individualized task-related contacts between teacher and pupils and a more active role for pupils. These results confirmed those from earlier research on children aged 4 and 5 years. Against expectation, class size did not affect pupil on-task behavior or peer interaction. There was a moderating role for school subject and a beneficial effect of teaching assistants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reciprocal Associations Between Adolescent Sexual Activity and Quality of Youth-Parent Interactions.

The authors examined differences in adolescents' relationships with their parents before and after adolescent first sexual activity. Participants were 13,570 members of the core sample of the National Longitudinal Survey of Adolescent Health (Add Health) Waves 1 and 2. Path analyses examined changes in parent-adolescent closeness, shared activities, and problem-focused interactions associated with changes in sexual activity separately for sons and daughters and for mothers and fathers. Race, religion, age, urbanicity, and parents' education were controls. Results confirm that increased problem-focused interactions and decreased parental closeness and shared activities both precede and follow adolescent sexual activity. Maintaining positive parental relations after adolescent first sexual activity is discussed as a means to reduce risks associated with sex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Resonant charge transfer in back-scattering of H-atoms from the Cs adsorbates on the Cs/Cu(1 1 1) surface

We use the wave packet propagation approach to study the dynamics of resonant charge transfer in hydrogen back-scattering from Cs adsorbates on Cu(1 1 1). The affinity level of the projectile strongly interacts with an adsorbate-localized state leading to an important modification of the projectile–substrate resonant charge transfer. At very low collision energies (<2.5 eV) the adiabatic evolution of the system leads to the blocking of the negative ion formation in back-scattering of neutral hydrogen atoms from Cs adsorbate. At higher energies non-adiabatic transitions exist, and negative ion formation is possible.