Corrosion failure probability analysis of buried gas pipelines based on subset simulation

Corrosion is the main reason for the failure of buried gas pipelines. For effective corrosion failure probability analysis, the structural reliability theory was adopted in this study to establish two calculation models for pipeline corrosion failure: the pressure failure model and von Mises stress failure model. Then, two calculation models for the corrosion failure probability were established based on a corrosion depth growth model obtained from actual survey data of soil corrosion characteristics. In an example, Monte Carlo simulation (MCS) and subset simulation (SS) were used to analyze the corrosion failure probability of pipelines, and the results were compared. SS can compensate for the shortcomings of MCS as it has higher computational efficiency and accuracy. Therefore, SS was adopted to simulate variations in the corrosion failure probability of buried pipelines with the service time for the two failure probability calculation models, which were applied to a natural gas pipeline located in a chemical industry park in Zhuhai, China. A sensitivity analysis was carried out on the relevant parameters that affect the failure probability. The results showed that multiple loads caused by the covering soil, residual stress, temperature differential, and bending stress have a non-negligible effect on the pipeline reliability. The corrosion coefficients gradually become the most important factors that affect the failure probability with increased service time. The proposed methodology considers the actual operating conditions of pipelines to provide a reliable theoretical basis for integrity management.     

Chemical ornaments of male lizards <Emphasis Type="Italic">Psammodromus algirus</Emphasis> may reveal their parasite load and health state to females

Evidence for parasite-mediated sexual selection has been found in many species that use visual ornaments to attract females. However, in many animals, variation in female responses to scents of parasitized males suggests that parasitic infections might also affect information conveyed by pheromones (i.e., chemical ornaments). Thus, pheromones might also function in parasite-mediated sexual selection. We show here that female lizards Psammodromus algirus responded differently to femoral gland secretions of males according to the parasite load and health of these males. Scents of healthier males elicited more tongue flicks (a chemosensory behavior) by females, suggesting that these scents were more attractive. Chemical analyses showed that parasite load and the T-cell-mediated immune response were related to the variability in the proportions of some lipids in secretions of males. Further trials testing the chemosensory responses of females to chemical standards indicated that females actually discriminated the chemicals related to males’ health from other chemicals found in secretions. We suggest that these chemical ornaments may provide reliable information on the health and degree of parasitic infection of a male.     

Female benefit,male risk: Polyandry in the true armyworm Pseudaletia unipuncta

In Lepidoptera polyandry is common and females may increase their lifetime reproductive output through repeated matings if they acquire essential resources from male ejaculates. However, the paternity of males mating with previously-mated females is far from assured unless sperm precedence is absolute. In this study on the polyandrous armyworm, Pseudaletia unipuncta, we used two strains of male (the black-eyed wild type and a red-eyed homozygous, recessive mutant), mated with red-eyed females, to determine (i) whether male investment has any impact on female reproductive output, and (ii) if females do benefit from multiple matings, to what extent males fertilize the eggs to which they contributed. Multiple mating resulted in a significant increase in both the fecundity and longevity of females. However, the degree of sperm precedence (those eggs fertilized by the second male) varied from 0–100%, but was not affected by either male size or age, or by the duration of copulation. In cases where sperm precedence was <50% (x = 12%) females produced significantly more eggs (1384 versus 940) prior to the second mating than females where sperm precedence was >50% (x = 89%), indicating that the quality of the first mating influenced the fertilization success of the female's second mate.     

Diet quality affects an attractive white plumage pattern in dark-eyed juncos (Junco hyemalis)

Sexually selected traits that act as signals of quality often display some degree of condition dependence. In birds, condition dependence of ornamental plumage is often mediated by production costs related to acquisition or allocation of dietary resources. White plumage ornaments, however, have often been assumed to be inexpensive because their production requires neither pigment nor specialized feather structure. In male dark-eyed juncos (Junco hyemalis), the size of a white patch on the tail contributes to attractiveness and mating success. Using captive males, we examined the effects of diet quality on the size and brightness of the tail-white patch. After removing four tail feathers to induce replacement, we maintained subjects on a subsistence (low-protein) or enriched (high-protein) diet while induced feathers grew. Birds that received an enriched diet grew their feathers more quickly and grew larger, brighter white patches. Feather growth rate was positively correlated with the increase in the size of the tail-white patch, a relationship that was stronger in the subsistence diet group. However, within diet treatments, faster-grown feathers were slightly duller. Taken together, these results suggest that variation in diet quality may lead to condition-dependent expression of tail white and that condition dependence may be stronger in more stressful environments. We suggest a mechanism by which increased feather growth rate may lead to an increase in the size of the tail-white patch and discuss potential trade-offs between signal size and brightness.     

Unusual echolocation behavior in a small molossid bat, <Emphasis Type="Italic">Molossops temminckii,</Emphasis> that forages near background clutter

When searching for flying insects, Molossops temminckii uses unusual echolocation calls characterized by upward modulation of frequency vs time (UFM). Call frequency increases asymptotically in the relatively long (∼8 ms) pulses from a starting frequency of ∼40 kHz to a long narrowband tail at ∼50 kHz. When approaching a prey, the bat progressively increases the duration of calls and intersperses in the sequence broadband downwardly frequency-modulated signals with a terminal frequency of about 53 kHz, which totally replaces the UFM signals at the end of the approach phase. The sequence progresses to a capture buzz resembling those from other molossid and vespertilionid bats. The M. temminckii wing morphology is characterized by an average aspect ratio and a high wing loading, suggesting that it is more maneuverable than the typical Molossidae but less than typical Vespertilionidae. M. temminckii regularly forages near clutter, where it needs to pay attention to the background and might face forward and backward masking of signals. We hypothesize that the UFM echolocation signals of M. temminckii represent an adaptation to foraging near background clutter in a not very maneuverable bat needing a broad attention window. The broadband component of the signal might serve for the perception of the background and the narrowband tail for detection and perhaps classification of prey. Bats may solve the signal masking problems by separating emission and echoes in the frequency domain. The echolocation behavior of M. temminckii may shed light on the evolution of the narrowband frequency analysis echolocation systems adopted by some bats foraging within clutter.     

Fitness benefits of multiple mating versus female mate choice in the cellar spider (Pholcus phalangioides)

Recent studies have demonstrated that mating with multiple males can be beneficial for females and her offspring even if males contribute nothing but sperm. This was mainly established for species in which sperm from several males mix in the reproductive tract of the female, thus allowing sperm competition and/or female sperm choice. However, in species with last male sperm precedence, female re-mating decides against the previous male by strongly limiting his reproductive success. We tested the effect of female re-mating behaviour using the cellar spider Pholcus phalangioides, which shows strong last males sperm precedence and moderate levels of polyandry under natural situations. We predicted that females prevented from remating even though they are receptive would show reduced reproductive success compared to females that accept two copulations and females that reject a second male, since the latter two treatments were allowed to behave according to their decisions. However, if the number of matings per se had an effect on oviposition or on offspring performance, double-mated females should perform better compared to both treatments of once-mated females. We measured female fecundity and fertility over a period of 140 days, comparable to the species' natural reproductive peak season. Two thousand one hundred and fifty-two offspring from 67 first egg sacs were reared under two feeding levels. We registered development time and survival, and measured offspring adult size and mass. We found a positive effect of double mating, as in this treatment, oviposition probability was higher compared to the other treatments. Interestingly, adult female offspring of the DM treatment that were raised under low food level had a higher condition index compared to those from FS and RM, but development time, size and mass at adulthood were not affected by mating treatment. Female choice only seemed to affect hatching latency of the offspring. Overall, the main predictor of female reproductive output and success was female body size.     

总量控制费用分摊的多目标规划模型及解法

文章指出了污染物总量控制规划中公平合理分摊优化治理投资费用的重要性，分析了现有的优化治理投资费用分摊方法存在的问题，建立了公平合理分摊优化治理投资费用的多目标规划模型，提出用最短距离理想点法加以求解，并通过实例验证了该方法的合理性。结果表明该模型及解法既可以保证总量控制规划方案的社会整体效益最大，又不失公平，从而确保总量控制规划方案的顺利实施。     

Progress in developing an ANN model for air pollution index forecast

An air pollution index (API) reporting system is introduced to selected cities of China for public communication on air quality data. Shanghai is the first city in China providing daily average API reports and forecasts. This paper describes the development of an artificial neural network (ANN) model for the API forecasting in Shanghai. It is a multiple layer perceptron (MLP) network, with meteorological forecasting data as the main input, to output the next day average API values. However, the initial version of the MLP model did not work well. To improve the model, a series of tests were conducted with respect to the training method and structure optimization. Based on the test results, the training algorithm was modified and a new model was built. The new model is now being used in Shanghai for API forecasting. Its performance is shown reasonably well in comparison with observation. The application of the old model was only weakly correlated with observation. In 1-year application, the correlation coefficients were 0.2314, 0.1022 and 0.1710 for TSP, SO₂ and NO_x, respectively. But for the new model, for over 8 months application, the correlation coefficients are raised to 0.6056, 0.6993 and 0.6300 for PM₁₀, SO₂, and NO₂. Further, the new algorithm does not rely on manpower intervention so that it is now being applied in several other Chinese cities with quite different meteorological conditions. The structure of the model and the application results are presented in this paper and also the problems to be further studied.     

Female choice in the opportunistic mating of wild chimpanzees (Pan troglodytes schweinfurthii) at Mahale

For female chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania, the most common mating pattern is opportunistic. In such opportunistic matings, females copulated promiscuously but not randomly. This study describes female mate choice during 1-year observation of six females who exhibited regular genital-swelling cycles. During the study period, 169 opportunistic matings and four restrictive matings were recorded over the course of 51 days. As female estrus progressed, mating frequency and the number of adult male mating partners increased, although the number of potential mating partners did not change. Criteria of female choice examined were the direction and consent/rejection of courtship, proximity maintenance, and female grooming. Adult-male courtships were successful more often than those of adolescent males. During the earlier phase of estrus, females copulated rather promiscuously with many males. But during the later phase of estrus when the likelihood of conception is expected to be highest, they copulated repeatedly with high-ranking adult males. There was a positive correlation between female grooming frequency and mating frequency when the likelihood of conception was greatest. Female chimpanzees are thought to choose high-ranking males as fathers of their offspring. Moreover, female chimpanzees may adopt one or both of two mating strategies, i.e., a many-male strategy and a best-male strategy. Received: 23 November 1998 / Received in revised form: 12 April 1999 / Accepted: 26 April 1999     

Multiple mating and facultative polygyny in the Panamanian leafcutter ant Acromyrmex echinatior

Queen mating frequency of the facultatively polygynous ant Acromyrmex echinatior was investigated by analysing genetic variation at an (AG)_n repeat microsatellite locus in workers and sexuals of 20 colonies from a single Panamanian population. Thirteen colonies were found to be monogynous, 5 colonies contained multiple queens, whereas the queen number of 2 colonies remained unresolved. Microsatellite genotypes indicated that 12 out of 13 queens were inseminated by multiple males (polyandry). The mean queen mating frequency was 2.53 and the mean genetically effective paternity frequency was 2.23. These values range among the highest found in ants, and the results are in keeping with the high mating frequencies reported for other species of leafcutter ants. Consistent skew in the proportional representation of different patrilines within colonies was found, and this remained constant in two consecutive samples of offspring. Dissections showed that all examined queens from multiple-queen colonies were mated egg-layers. The mean relatedness value among nestmate workers in polygynous colonies was lower than that for monogynous colonies. No diploid males were detected in a sample of 70 genotyped males. Worker production of males was detected in one queenless colony. We discuss our findings in relation to known patterns of multiple maternity and paternity in other eusocial Hymenoptera. Received: 2 September 1998 / Received in revised form: 3 February 1999 / Accepted: 7 February 1999