Multimodal interactions in insect navigation

Animals travelling through the world receive input from multiple sensory modalities that could be important for the guidance of their journeys. Given the availability of a rich array of cues, from idiothetic information to input from sky compasses and visual information through to olfactory and other cues (e.g. gustatory, magnetic, anemotactic or thermal) it is no surprise to see multimodality in most aspects of navigation. In this review, we present the current knowledge of multimodal cue use during orientation and navigation in insects. Multimodal cue use is adapted to a species’ sensory ecology and shapes navigation behaviour both during the learning of environmental cues and when performing complex foraging journeys. The simultaneous use of multiple cues is beneficial because it provides redundant navigational information, and in general, multimodality increases robustness, accuracy and overall foraging success. We use examples from sensorimotor behaviours in mosquitoes and flies as well as from large scale navigation in ants, bees and insects that migrate seasonally over large distances, asking at each stage how multiple cues are combined behaviourally and what insects gain from using different modalities

Rotor instability due to a gear coupling connected to a bearingless sun wheel of a planetary gear

A 21 MW electric power generating unit comprises a gas turbine, a planetary gear, and a generator connected together by gear couplings. For simplicity of the design and high performance the pinion of the gear has no bearing. It is centered by the planet wheels only. The original design showed a strong instability and a natural frequency increasing with the load between 2 and 6.5 MW. In this operating range the natural frequency was below the operating speed of the gas turbine, n sub PT = 7729 RPM. By shortening the pinion shaft and reduction of its moment of inertia the unstable natural frequency was shifted well above the operating speed. With that measure the unit now operates with stability in the entire load range

Performance Evaluation of the Least-Cost Lumber Grade-Mix Solver

The least-cost lumber grade-mix problem is of high economic interest to industry. Finding the minimum grade or grade-mix for a given cutting bill can save a company large sums without incurring additional costs. To academia, the least-cost lumber grade-mix problem is of significance due to its complexity and the difficulty to obtain near optimal or optimal results.An earlier study used a new statistical approach to solving the least-cost lumber grade-mix problem. A five-factor mixture design was used to create a lumber grade-mix response surface, on which the minimum cost point is determined. However, this model's merit has never been assessed so far. This study compares the performance of the new statistical model with solutions derived from the widely used OPTIGRAMI 2.0 least-cost lumber grade-mix program.Results revealed that the statistical optimization approach provides better overall solutions for both raw material and total production cost scenarios. For 9 of 10 cutting bills tested, the statistical model found lower-cost solutions compared with those provided by OPTIGRAMI 2.0. The maximum savings found was $70/m3 of raw material (cost savings of 9$105/m3 when processing costs were included (cost savings of 10%). Thus, the new model has the potential to help wood products manufacturers decrease their material and processing costs. This model has been incorporated into ROMI, the USDA Forest Service's rough-mill simulation tool

Investigating the Linearity Assumption Between Lumber Grade Mix and Yield Using Design of Experiments (DOE)

Solving the least-cost lumber grade mix problem allows dimension mills to minimize the cost of dimension part production. This problem, due to its economic importance, has attracted much attention from researchers and industry in the past. Most solutions used linear programming models and assumed that a simple linear relationship existed between lumber grade mix and yield. However, this assumption has never been verified or rejected with scientific evidence. The objective of this study was to examine whether a linear relationship exists between yield and two- and three-grade lumber combinations using the USDA Forest Service's ROMI-RIP rough mill simulator and a cutting bill created by Buehlmann. The results showed that a simple linear relationship between grade mix and yield exists only for some grade combinations, but not for others. These findings were confirmed by repeating the tests using actual cutting bills from industry. It was observed that cutting bill characteristics, especially part length requirements and the lumber grades involved, are influential in causing a simple linear or nonlinear relationship between grade mix and yield

Effect of Cutting Bill Requirements on Lumber Yield in a Rip-First Rough Mill

In recent years, producers of solid wood dimension parts have emphasized improvements in lumber yield, focusing primarily on lumber grade and cutting technology rather than cutting bill design. Yet, cutting bills have a significant impact on yield. Using rip-first rough mill simulation software, a data bank of red oak lumber samples, and a cutting bill that resembles those used in industry, we determined the effect of changes in part size within an existing cutting bill and the impact of part-quantity requirements on yield. The results indicated that cutting bill requirements have a large influence on yield when the shortest part length in the bill is changed. Medium-length part sizes also affect yield except when the cutting bill requires an unlimited number of small parts; in this case, yield always will be high. When an all-blades-movable arbor is used, length changes in the bill affect yield more than changes in width. This study reveals our current lack of understanding of the complex relationship between cutting bill and lumber yield, and points out the yield gains that are possible when properly designed cutting bills are used

Brief report: quality of life is impaired in pediatric burn survivors with posttraumatic stress disorder

OBJECTIVE: This study assessed health-related quality of life (HRQOL) and posttraumatic stress disorder (PTSD) in pediatric burn survivors and examined associations between PTSD and HRQOL. METHODS: Forty-three burn survivors, ages 7-16 years, were interviewed at an average of 4.4 years after their accident using the Clinician-Administered PTSD Scale for Children and Adolescents and the TNO-AZL Child Quality of Life Questionnaire. RESULTS: Eight children (18.6%) met DSM-IV criteria for current PTSD. While most dimensions of HRQOL were within normal limits, social functioning was impaired. Severity of PTSD was significantly associated with physical, cognitive, and emotional dimensions of HRQOL. Children with PTSD reported an impaired overall HRQOL and limited physical (e.g., more bodily complaints) and emotional functioning (e.g., more feelings of sadness). CONCLUSIONS: This study provides tentative evidence for a considerably high prevalence of PTSD in pediatric burn survivors and for a negative association between PTSD and HRQO

Flexible weighing of olfactory and vector information in the desert ant Cataglyphis fortis

Desert ants, Cataglyphis fortis, are equipped with remarkable skills that enable them to navigate efficiently. When travelling between the nest and a previously visited feeding site, they perform path integration (PI), but pinpoint the nest or feeder by following odour plumes. Homing ants respond to nest plumes only when the path integrator indicates that they are near home. This is crucial, as homing ants often pass through plumes emanating from foreign nests and do not discriminate between the plume of their own and that of a foreign nest, but should absolutely avoid entering a wrong nest. Their behaviour towards food odours differs greatly. Here, we show that in ants on the way to food, olfactory information outweighs PI information. Although PI guides ants back to a learned feeder, the ants respond to food odours independently of whether or not they are close to the learned feeding site. This ability is beneficial, as new food sources—unlike foreign nests—never pose a threat but enable ants to shorten distances travelled while foraging. While it has been shown that navigating C. fortis ants rely strongly on PI, we report here that the ants retained the necessary flexibility in the use of PI

Multimodal influences on learning walks in desert ants (Cataglyphis fortis)

Ants are excellent navigators using multimodal information for navigation. To accurately localise the nest at the end of a foraging journey, visual cues, wind direction and also olfactory cues need to be learnt. Learning walks are performed at the start of an ant’s foraging career or when the appearance of the nest surrounding has changed. We investigated here whether the structure of such learning walks in the desert ant Cataglyphis fortis takes into account wind direction in conjunction with the learning of new visual information. Ants learnt to travel back and forth between their nest and a feeder, and we then introduced a black cylinder near their nest to induce learning walks in regular foragers. By doing this across days with different wind directions, we were able to probe how ants balance different sensory modalities. We found that (1) the ants’ outwards headings are influenced by the wind direction with their routes deflected such that they will arrive downwind of their target, (2) a novel object along the route induces learning walks in experienced ants and (3) the structure of learning walks is shaped by the wind direction rather than the position of the visual cue

The Influence of Cutting-Bill Requirements on Lumber Yield Using a Fractional-Factorial Design Part I. Linearity and Least Squares

The importance of lumber yield on the financial success of secondary solid wood products manufacturers has been known for quite some time. Various efforts have been undertaken to improve yield, such as inclusion of character marks (defects) in parts, "cookie-cutting" of boards, improved optimization algorithms, or improved cut-up technologies. For a variety of reasons, the relationship between cutting-bill requirements and lumber yield has attracted limited attention. This is Part I of a 2-part examination of this relationship.The standardized and simplified Buehlmann cutting bill and the Forest Service's Romi-Rip lumber cut-up simulator were used in this study. An orthogonal, 220-11 fractional-factorial design of resolution V was used to determine the influence of different part sizes on lumber yield. All 20 part sizes contained in the cutting bill and 113 of a total of 190 unique secondary interactions were found to be significant variables in explaining the variability in observed yield. Parameter estimates for the part sizes and the secondary interactions were used to specify the average yield contribution of each variable. Parts 445 mm long and 64 mm wide were found to have the most positive influence on yield. Parts smaller than 445 by 64 mm (such as, for example 254 by 64 mm) had a less pronounced positive yield effect because their quantity requirement is relatively small in an average cutting bill. Thus, the quantity required is obtained quickly during the cut-up process. Parts with size 1842 by 108 mm, on the other hand, had the most negative influence on high yield. However, as further analysis showed, not only the individual parts required by a cutting bill, but also their interaction determines yield. In general, it was found that by adding a sufficiently large number of smaller parts to a cutting bill that required large parts, high levels of yield can be achieved