冲模间隙对产品质量及模具寿命的影响

通过对不同间隙条件下冲裁件断面质量以及不同间隙条件下模具的磨损情况,分析说明了冲模间隙与模具磨损和产品质量间的关系。     

计算冲裁间隙的实用公式

此文按照冲裁间隙的传统计算公式及经验数据,总结出了冲裁模合理间隙的实用计算公式。     

太白山红桦林林隙特征的研究

对太白山红桦林林隙的一般特征和干扰状况进行了初步研究,分析了植被中林隙的数量、类型及成因,并对林隙形成木的类型、数量、物种构成和径级结构做了分析.结果表明,太白山红桦林林隙以自然立枯形成的最多;林隙线状密度为23.5个/km;冠空隙面积在20～80m2范围内的最多,冠空隙总面积占整个林分面积的4.7%;扩展林隙的面积在50～100m2范围内的最多,占整个林分的11.9%;林隙的形成木以红桦为主,径级在20～40cm范围内的占绝大部分;在太白山红桦林中,大多数的林隙由1～3株林隙形成木形成,其中单株形成木形成的林隙最多,每个林隙的林隙形成木平均为1.51株;林隙的腐烂等级为C级的分布较多;冠空隙径高比多分布在0.30～0.45之间,扩展林隙径高比多分布在0.60～0.80之间;林隙内幼苗主要有红桦、华山松,在大面积的林隙内红桦幼苗占绝对优势.图1表5参26     

The timing of chemical signaling with urine in dominance fights of male lobsters (Homarus americanus)

Chemicals carried in the urine are a rich source of information about the identity, sex, aggressive motivation, and other attributes of an animal. In agonistic interactions, animals should be careful about disclosing such information, since it can be used by receivers to the disadvantage of the sender. By adjusting the timing of urine release, the signaler may still influence the behavior of the receiver to its own benefit. Here we investigate the urine signaling of American lobsters (Homarus americanus), necessary for the maintenance of dominance, using a catheter technique with high temporal resolution. We hypothesize that urine release in lobster fights is not continuous but restricted to moments that may elicit a reaction in the receiver beneficial to the sender. We found that eventual winners signaled more readily in the initial phase of the fight. Eventual losers did not show such initial urination. This suggests that a confident lobster may use urine signals to influence the behavior of its opponent into giving up the fight at an early stage. For both winners and losers, urine release is linked to offensive behavior and increases as the intensity of agonistic behavior increases. The coupling of urine release to offensive behaviors appears to improve both the reliability and efficacy of the chemical signal. Releasing urine under the increasing risk of inflicting injury during the fight provides a handicap that may ensure reliability of the threat signal. Furthermore, the immediate coupling of urine components to offensive behavior may help to consolidate the receiver"s memory of the signaler"s individual scent and thus facilitate future recognition of the dominant animal. Received: 6 October 1999 / Accepted 28 August 2000     

The use of waggle dance information by honey bees throughout their foraging careers

We studied the extent to which worker honey bees acquire information from waggle dances throughout their careers as foragers. Small groups of foragers were monitored from time of orientation flights to time of death and all in-hive behaviors relating to foraging were recorded. In the context of a novice forager finding her first food source, 60% of the bees relied, at least in part, on acquiring information from waggle dances (being recruited) rather than searching independently (scouting). In the context of an experienced forager whose foraging has been interrupted, 37% of the time the bees resumed foraging by following waggle dances (being reactivated) rather than examining the food source on their own (inspecting). And in the context of an experienced forager engaged in foraging, 17% of the time the bees initiated a foraging trip by following a waggle dance. Such dance following was observed much more often after an unsuccessful than after a successful foraging trip. Successful foragers often followed dances just briefly, perhaps to confirm that the kind of flowers they had been visiting were still yielding forage. Overall, waggle dance following for food discovery accounted for 12–25% of all interactions with dancers (9% by novice foragers and 3–16% by experienced foragers) whereas dance following for reactivation and confirmation accounted for the other 75–88% (26% for reactivation and 49–62% for confirmation). We conclude that foragers make extensive use of the waggle dance not only to start work at new, unfamiliar food sources but also to resume work at old, familiar food sources.     

Modulation of individual behavior and collective decision-making during aggregation site selection by the ant<Emphasis Type="Italic"> Messor barbarus</Emphasis>

Insect societies are often confronted with choices among several options such as food sources of different richness or potential nest sites with different qualities. The mechanisms by which a colony as a whole evaluates these situations and takes the appropriate decision are of crucial importance for its survival. Here we studied how collective decisions arise from individual behaviors when a group of workers of the ant Messor barbarus is given a choice between two aggregation sites. Two hundred ants were introduced into an arena and given a choice between two tubes connected to the arena. The tubes had different physical properties: dry and transparent (termed as dry), humid and transparent (termed as humid), or dry and dark (termed as dark). After 30 min, most ants were found to be aggregated in a humid tube when paired with a dry tube, or in a dark tube when paired with a humid one. When two humid tubes were in competition, ants aggregate more in one of the sites. The choice of ants was consistent throughout experiments. An analysis of individual behaviors shows that the probability of an ant recruiting and the intensity of its trail-laying behavior strongly depend on the quality of the tubes. Our study suggests that the selection of an aggregation site does not require that individual ants directly compare sites, but rather relies on the synergy between amplification processes involving recruitment by chemical trails, and a modulation of the individual resting time in a site as a function of its population.Communicated by L. Sundström     

Heterospecific song matching in two closely related songbirds (Parus major and P. caeruleus): great tits match blue tits but not vice versa

To date, song research has focused primarily on the interactions of conspecifics. However, frequent interactions of songbirds with heterospecifics may necessitate adequate communication outside the species boundary. In this study, we focus on heterospecific communication behaviour of two small sympatric congeneric passerines, great and blue tits (Parus major and Parus caeruleus), which breed in overlapping territories and compete for food and nesting cavities. By means of a first playback experiment, we show that (1) heterospecific matching (imitating songs of the other species) is a strategy frequently used by great tits but not by blue tits, (2) both blue tit trilled and untrilled song can be accurately matched by great tits and that (3) almost half of the great tits in our study population match at least one blue tit song across all studied breeding stages, indicating that this heterospecific matching behaviour is a common feature in this population. A second playback experiment showed that these great tit imitations of blue tit songs do not function in intraspecific communication between male great tits. Hence, these heterospecific imitations appear to be designed for interspecific communication with blue tits. These findings suggest a strong heterospecific influence on the vocal learning process, repertoire composition and repertoire use in great tits and provide a possible mechanism that can drive song convergence in songbirds.     

The neglected scent: on the marking function of urine in Lemur catta

In ring-tailed lemurs (Lemur catta) urine deposition can be combined with two different tail configurations: (i) tail held up in an evident display (urinate tail-up, UT-up); (ii) tail slightly raised to avoid its impregnation with urine (urinate tail-down, UT-down). We used both signaller- and receiver-based approaches to search for functional differences between these two kinds of urine deposition. We predicted that UT-up might be a complex signal combining olfactory and visual cues. We carried out observations and scent tests on four captive groups of ring-tailed lemurs. Group members sniffed/licked UT-up scents more frequently than UT-down ones. Moreover, UT-up showed peak levels during the mating season whereas UT-down did not. These findings suggest that urine can play a role in intra-group reproductive communication. Lemurs more frequently performed UT-up in a few drops and UT-down in streams. Recognition experiments clearly showed that individuals can discriminate between urine of their own group and urine from a foreign group (a necessary prerequisite for the use of urine in inter-group communication). The possible function of UT-up in inter-troop communication was supported by the higher frequency of this pattern along a fence separating two of the study groups. Moreover, in the presence of a dummy, the frequency of UT-up increased significantly. In conclusion, UT-up is a complex signal with multiple characteristics. By using different sensory channels, UT-up provides different types of information (location and signaller quality) and contains multiple messages directed both at group-members and neighbouring groups....to conceal this letter, the Minister had resorted to the comprehensive and sagacious expedient of not attempting to conceal it at all (from the Purloined letter E. A. Poe, 1845)     

Variations in Newspaper Coverage on Water in the U.S. Intermountain West

Water is a salient issue in the Intermountain West of the United States (U.S.), with concerns ranging from water scarcity and drought to intermittent flooding and water quality risks. This paper investigates coverage of water issues across seven newspapers in the core of the U.S. Intermountain West region. Newspapers have the potential to set agendas and influence perceived salience of issues among consumers. The Intermountain West region shares common concerns about water supply and demand, climate change, and water quality. We investigate whether or not local daily newspaper coverage of water issues provides a more local or regional sensitivity. Findings from this exploratory study reveal differences in water coverage across local daily newspapers. The overall volume of water‐related articles differed across newspapers as did proportion of articles on specific water topics and connecting issues. Coverage of local issues was more dominant than might be expected given mass media trends, but water geography in articles extended across the U.S. and the world in every newspaper studied. Variations in newspaper coverage of water issues suggests more local nuance persists despite the experience of common water issues across the region.     

Mineralogical characteristics and photocatalytic properties of natural sphalerite from China

Different natural sphalerites have a range of photocatalytic properties that can potentially be exploited for environmental remediation purposes. To develop value in the exploitation of sphalerite, samples were collected from 19 ore deposits in China and characterized for their mineralogical and photocatalytic properties. X-ray diffraction (XRD) and electron probe micro analysis (EPMA) measurements indicated that all the natural sphalerites from various localities crystallized in cubic phases with various chemical compositions. The substitution of Fe for Zn ranged from 0.235% to 14.826% by weight, Mn from 0.004% to 4.868%, Cu from 0.009% to 5.529% and Cd from 0.133% to 1.576%. As Fe became more abundant, the color of natural sphalerite darkened, becoming almost black; and higher Fe content was associated with stronger visible light absorption. Photoluminescence spectra showed emission mainly related to S-vacancies and progressively decreasing fluorescence intensity with increasing Fe content. Tests of the photocatalytic degradation of methyl orange indicated that the sample with the highest Cd content but moderate Fe content had the highest photocatalytic activity. Specifically, the degradation of Methyl Orange (30 mg/L) attained 82.11% efficiency under visible light irradiation for 4 hr of natural sphalerite with 4.262% Fe and 1.576% Cd. Overall, the Fe content in sphalerite was found to contribute to the visible light absorption ability and the recombination rate of photo-generated electrons and holes, while substitution by Cd was observed to have a greater effect on the photocatalytic properties. These findings provide a scientific basis for the profitable utilization of base metal resources like sphalerite.