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The effects of two possible factors, prevention of pest immigration and enhancement of natural enemies, in suppressing onion thrips, Thrips tabaci L., were estimated in a small-scale experimental system of spring-planted onions intercropped with barley. The population dynamics of the thrips and their potential predatory natural enemies were investigated in four treatments: control (bare ground), insect net barrier, and onion-barley intercropping with or without trimming. We found that intercropping significantly suppressed onion thrips. It is unlikely that this effect was due to the prevention of thrip immigration because they seemed to move over the camouflage and/or physical barriers of the barley and the net barrier surrounding the onions easily. Intercropping with barley significantly increased hoverfly (Syrphidae) larvae numbers on onion leaves, and that of some groups of ground-dwelling predators such as large carnivorous ground beetles (Carabidae), ants (Formicidae), and wolf spiders (Lycosidae). We conclude that the suppression of thrips in this system was associated with the enhancement of hoverfly larvae abundance, mainly Sphaerophoria macrogaster (Thomson) (Syrphidae: Diptera) because they were observed together with thrips on onions and have been reported to predate thrips as well as aphids. Some hoverfly larvae on barley might move to nearby onions to search for new food sources and attack thrips.

The larval parasitoid Diadegma hiraii (Kusigemati) was evaluated as a potential biological control agent of the soybean pod borer, Leguminivora glycinivorella (Matsumura). The timing of adult emergence after overwintering was ascertained, and land-use factors that enhance population density were analyzed. Host cocoons were collected and exposed to different temperatures and photoperiod regimes. Subsequently, the emergence of parasitoid was monitored. Land-use types were categorized into 4 land-use types (Poaceae, Fabaceae, Brassicaceae, and forest). Adult parasitoid emergence was dependent on temperature, but largely unaffected by photoperiod. The estimated emergence time of parasitoid was 3 months before the occurrence of the host, suggesting that the overwintered generation may lay eggs in alternate hosts. Parasitism rate was positively correlated with the area covered by Poaceae plants within a 500-m radius of the soybean field. Based on the results of the overwintering ecology and landscape analysis, D. hiraii probably completes its life cycle in the agroecosystems. The parasitoid’s effectiveness as a biological control agent may be influenced by the arrangement of land-use types in the agroecosystems surrounding soybean fields. However, the pest control provided by D. hiraii is limited because of approximately 30% of parasitism rate. Consequently, a combination of this species and cultural control and/or other biological control agents is suggested for sustainable soybean cultivation.

Whether the caste fate of social insects is determined before or after emergence is a key question for understanding the evolution of eusociality. Paper wasps are a suitable model for answering this question because there are no critical morphological differences between queens and workers in paper wasps, and these animals appear to represent an early stage of eusociality. We explored the above question by determining the effects of photoperiod during the adult stage on caste-fate determination in the paper wasp Polistes jokahamae. We collected colonies at different stages in the field and exposed emerging adults individually to long or short days. Under these isolated conditions, gyne-destined (diapausing) females were expected to exhibit large lipid stores without mature eggs, while the reverse was expected to be true for worker-destined (nondiapausing) females. The proportion of wasps with mature eggs was higher under long days in the second and subsequent broods, but not in the first brood. Lipid stores were larger among large females and under short days, and smaller for the first brood. These findings together suggest that the first brood emerges with a strong preimaginal bias toward workers (nondiapausing form), whereas the other broods emerge with no bias or an easily reversible bias. However, it is difficult to conclude whether the bias came from body size or the season of emergence. We discuss the possibility that the ancestor of paper wasps had workers with and without preimaginal bias toward becoming workers at emergence.

To understand the geographical differences between diapause systems and synchronization of adult occurrence in the soybean pod borer Leguminivora glycinivorella (Lepidoptera: Tortricidae), we examined the timing of winter diapause termination and intensity of summer diapause using univoltine and potentially bivoltine individuals in Iwate, Japan. In laboratory rearing experiments of mature larvae maintained at constant temperature (20 °C), winter diapause intensity weakened by January without photoperiodic responses. Meanwhile, summer diapause was maintained by the long day length and presumably terminated with the photoperiodic transition from long to short day length. The intensity of summer diapause was stronger for cocoons that transitioned from a 16 h light to 8 h dark (LD 16:8) to a LD 15:9 photoperiod than for those that transitioned from LD 15:9 to LD 14:10. These results suggest that populations distributed in relatively low-latitude areas, with partly or potentially bivoltine individuals, would have a weaker summer diapause or none at all. Moreover, sexual differences in the number of days to emergence were not detected when individuals experienced a photoperiodic transition from long to short day length, suggesting that the summer diapause system may function to synchronize the emergence of males and females in the population examined.

Background Inter-regional relationships between landscape factors and biological responses in natural conditions are important but difficult to predict because of the differences in each landscape context and local environment. To examine the inter-regional variability in relation to landscape factors and the biological response of an insect pest of rice, Stenotus rubrovittatus, we extrapolated a damage prediction model (the ‘original model’ of our previous study) for rice using land-use data. The ‘original model’ comprised as fixed factors the area of source habitat (i.e. pastures and graminoid-dominated fallow fields), soybean fields, and rice paddies within 300-m radii with research years as the random intercept. We hypothesized that the original model would be applicable to new regions, but the predictive accuracy would be reduced. We predicted that fitting a new extended model, adjusting the parameter coefficients of identical fixed factors of the ‘original model,’ and adding regional random intercepts would improve model performance (the ‘extended model’). A field experiment was conducted in two regions that had a similar landscape context with the original region, each in a different year of four years in total. The proportion of rice damage and surrounding land use within a 300-m radius was investigated, and the data were applied to the models and the applicability and accuracy of the models were examined. Results When the ‘original model’ was assigned to the combined data from the original and extrapolated regions, the relationship between the observed and the predicted values was statistically significant, suggesting that there was an inter-regional common relationship. The relationship was not statistically significant if the model was applied only to the new regions. The extended model accuracy improved by 14% compared with the original model and was applicable for unknown data within the examined regions as demonstrated by three-fold cross validation. Conclusions These results imply that in this pest–crop system, there is likely to be a common inter-regional biological response of arthropods because of landscape factors, although we need to consider local environmental factors. We should be able to apply such relationships to identify or prevent pest hazards by offering region-wide management options.

Space–time variation of the free-surface roughness pattern, due to sub-surface turbulence, is one of the most important features of turbulent open-channel flows. Despite its importance, the free-su...

In the temperate paper wasp Polistes jokahamae, caste is influenced by photoperiod during the adult stage, but the mechanisms underlying the caste-fate determination system have been unclear. We measured the brain levels of monoamines and related substances in females kept isolated for two weeks under different photoperiods. Except for in the first-emerging group, the females developed ovaries under long-day conditions, whereas they stored lipids under short-day conditions. The levels of tyramine in the brain were significantly higher under long-day than under short-day conditions and positively correlated with maximum oocyte lengths. These results suggest that tyramine was produced in response to long daylength during the adult stage and associated with ovarian development, which is the principal characteristic of reproductive workers. There was also a significant positive correlation between dopamine levels in the brain and maximum oocyte length, independent of photoperiod, suggesting that dopamine is involved in reproductive function with tyramine resulting in the induction of reproductive workers. Meanwhile, higher levels of tryptophan in the brain were found in short-day conditions and positively correlated with lipid stores. However, serotonin synthesized from tryptophan and N-acetylserotonin were not associated with lipid stores without photoperiodic responses, suggesting that tryptophan is involved in the physiological changes toward gyne under short daylength, independently of serotonin signaling. In conclusion, tyramine and tryptophan are candidates for mediating photoperiod-dependent caste-fate determination in P. jokahamae: the former is involved in generating the worker caste while the latter is involved in generating the gyne caste.

Workers and gynes (potential queens for the next spring) of temperate paper wasps are distinguishable based on their lipid stores a few weeks after emergence. However, it was not known whether the lipid stores of worker- and gyne-destined females differ at emergence. Newly emerged females of Polistes jokahamae were divided into three categories: the first brood, comprising worker-destined individuals that are nursed only by the queen; the second brood, comprising worker- and gyne-destined individuals that are nursed by the queen and workers and emerge before male emergence; and the third brood, comprising gyne-destined individuals that emerge after the emergence of the first males. The first brood produced smaller and lighter adults with lower lipid stores. These lipid stores were lower even after adjusting for head width, which suggests the presence of a preimaginal bias toward worker caste; such a bias was not detected in the second brood. After adjusting for head width, lipid stores increased with the wet mass in the second and third broods but not in the first brood, suggesting that the component proportion of lipid stores increased but that of some other nutrients decreased with increasing wet mass in the first brood. In addition, the head width, wet mass, and lipid stores (including lipid stores divided by the head width cubed) in the first brood increased with the emergence order, whereas the fatness (wet mass divided by the head width cubed) did not.

Parasitoid researchers have generally thought that the body size of the mother parasitoid does not affect the fitness performance of the progeny during the immature stage, as long as the progeny develop in the same environment. We reveal for the first time that this is not true for the parasitoid Echthrodelphax fairchildii (Hymenoptera: Dryinidae), which is parasitic on planthoppers. Large females ensured an increased survival rate for their progeny during the immature stage and a large body size at adult emergence. Maternal body size differentially affected the body sizes and survival rates of male and female progeny. Small females did not produce female progeny, and the survival rate of the female progeny increased more steeply with increasing maternal body size than that of the male progeny. Meanwhile, the body size of male progeny increased more steeply with increasing maternal body size. The influence of maternal body size on progeny survival to adult emergence has never been reported in insects before. In addition, large females were more likely to lay female eggs, suggesting that females control the sex ratio of progeny in response to their own body size.

The behaviors performed on the nest by the foundress queen and workers of the paper wasp Polistes jokahamae were observed in three colonies in the field and one colony in a cage set in the field. Each queen was rarely ranked top in the dominance hierarchy determined by the pairwise dominance–subordinate interactions and did not display more frequent direct aggression toward the top-ranked worker than toward other workers. Furthermore, the queen exhibited aggression less frequently than did the most aggressive workers in all four colonies. The dominance order among the workers was positively correlated with the emergence order, with older workers being more dominant. The queen laid eggs in a dominant or monopolized way; some dominant workers laid eggs in three colonies. These observations suggest that the queen maintained her queen status, including her reproductive priority, using signals rather than aggression. Lateral vibrations (rapidly laterally vibrating the abdomen) and abdominal rubbing (rubbing the abdomen onto the comb) appeared to be candidate signals of the fertility or reproductive potential of the performer. Lateral vibrations were performed only by the queen, and their frequency was positively correlated with the frequency of ovipositing. The queen and some dominant workers performed abdominal rubbing; the frequency was higher for the queen than for any of the dominant workers early in the colony’s development, but not later. Although performers of abdominal rubbing were more likely to lay eggs than non-performers, the frequency of abdominal rubbing was not a predictor of the frequency of ovipositing.

Independent-founding paper wasps constitute a major group of primitively eusocial insects, and when caste-fate determination occurs in temperate species of these wasps, particularly regarding whether it occurs before or after emergence, remains unclear. No critical morphological differences occur between potential queens of the next generation (often called gynes) and workers in primitively eusocial insects. The gynes of temperate species are characterized by diapausing, and the nutrients available during the larval stage have often been believed to determine caste fate. Short days usually induce diapause in temperate nonsocial insects, although few investigations of the effects of day length on caste-fate determination in paper wasps have been conducted. By exposing individuals to different combinations of short and long days during the immature and adult stages, we show for the first time that short days during the adult stage (but not during the immature stage) facilitated caste-fate determination toward gynes in a paper wasp. Moreover, the decision to diapause partly depended on changes in the photoperiod during the pupal and adult stages. The size of the adult also affected caste-fate determination, with diapause more likely to occur in large adults, but this size effect did not occur when individuals were exposed to many short days during the pupal stage. In addition, all adults except for a small proportion of smaller individuals prepared for diapause under short days. These findings suggest that the photoperiod is a higher priority cue than adult size.

In the applications of the Large eddy simulation (LES) to open-channel flows with roughness, water surface is usually treated as a fixed boundary by neglecting the effects of surface fluctuation generated by boil vortices or relatively large surface variations caused by the drag force at each roughness element. In the present study, in order to expand the applicability of LES to such general conditions, the bottom topography is treated by introducing the immersed boundary method and the free surface variation is simulated by introducing a density function. It was made clear that the developed model is capable to represent relatively large surface variations in the strip-roughness flows with various roughness spacings. The numerical results agreed fairly well with those obtained by PIV.

Water surface velocity field is affected by the three dimensional flow structures under the water. Typically, some of the separation vortices generated near the bottom ascend up to the water surface which causes the diversion of surface floating particles. These vortices, usually called the boil vortices in the field of river engineering, can be commonly observed in natural streams with relatively large roughness. In order to make clear the characteristics of such boil vortices appeared on the water surface, horizontal flow fields at the water surface of flows with several strip roughness are visualized by tracer particles. The visualized images are processed by multiply superposing the images viewed from a frame moving with the surface velocity. It is shown that superposed images clearly emphasize the flow features showing artistic patterns generated by floating tracers.

River bed is composed of movable material such as sand or grain and small or large scale vortices are generated at the bed, which are generally lifted upward making confliction with water surface. The confliction of vortices against the water surface yields surface ripples making water-surface configuration rather complicated. Although there are a large number of researches on rough bed flows, the interrelationship between flow and water surface has not been clarified so far. In order to investigate fundamental features of flows with rough walls, measurements are made for the flows with strip roughness. A numerical simulation by LES is also performed to compare with the experimental results, showing a reasonable agreement with the experiments.

Overview A computational model is developed for simulations of transient behavior of PEFC stack under realistic driving conditions. This model is applied to simulations of internal states of cells stack (maximum output about 100kW) with an injector, an exhaust and a recirculation system. Transient internal states under pressure swing and purging process are calculated. The physical model is based on so-called 2D + 1D model, which takes into account overall transport phenomena in PEFC fuel cell systems, such as transport of gas species and liquid water, thermal balance, electrochemical reactions and current distributions. Injector and exhaust systems are modeled by boundary conditions. Transient internal states, including fuel flow distributions between stacked cells and cell performance change at purging process will be demonstrated. Possible applications of those simulations to designing fuel cell stack control system will be discussed. Numerical Modeling and Results Simulation is performed by our own simulation software for PEFCs, which is capable of simulating full-stack fuel cell system for fuel cell vehicles (up to 400 cells) under transient operating conditions. An important feature of this software is that macroscopic models are applied for electrochemical reactions and transport phenomena in the MEA. Heat transfer and fluid dynamics of liquid-gas two phase fluid with phase changing are also taken into account. These models are coupled with multi-dimensional heat and mass transport equations, including effective parameters for gas diffusivity and permeability in the GDL and equivalent hydraulic diameter in the flow channel. This software can also simulate cathodic degradation by carbon corrosion reactions. Computational models of cell stack (250 cm2 reaction area in each cells) are constructed. A numerical model of anode system is constructed by adding transient boundary conditions for an injector and an exhaust system with an ejector valve. An interconnect boundary condition between inflow and outflow manifolds are also introduced as a computational model of recirculation system. These transient boundary conditions represent open / close timings of injector and ejector under actual driving conditions. Distributions and consumptions of hydrogen, build-up of cross-leak nitrogen and condensate liquid water can be calculated under transient (maximum output is about 100kW) loading. Simulated results show transient behavior of the stacked cell system, for example, Build-up of cross-leak nitrogen and condensate liquid water under transient loading conditions, and their effects on the distribution of performances between stacked cells. Evolution of fuel flow distribution between stacked cells under pressure swing. Efficiency of purging process and change of performance before and after purging. Those results can be calculated for various configurations of cells and driving conditions, and relations between stacked cell behaviors and those conditions can be discussed. Those discussions can provide useful information for improving durability of stacked cells by avoiding depletion of hydrogen, and / or examinations of control schemes which can efficiently utilize hydrogen fuel.

In this paper we describe the analysis of the effects of the specific heat of a regenerator material on the refrigeration capacity of a 4K-GM (Gifford-McMahon) refrigerator. The findings revealed by the analysis are given below. When the specific heat of the regenerator material is changed from 1.5 J/(K·cm3) to 0.01 J/(K·cm3), the no-load temperature is changed from 2.11 K to 26.9 K. The lowest temperature that can be theoretically attained in this refrigerator is the temperature around the λ point of helium. It is sufficient for the regenerator material to provide a specific heat of 0.8 J/(K·cm3). The refrigeration capacity is found to be superior over a wider temperature range when the specific heat distribution is uniform than when it has a peak. When different kinds of regenerator materials are stacked, the material stacked at the cold part of the regenerator may have a low specific heat at high temperatures, but the material stacked at the hot part of the regenerator should have a high specific heat at low temperatures.

This paper describes the numerical simulation of a GM refrigerator operating at about 4 K. The simulation model is composed of a regenerator, an expansion space, and a cooling stage. The volumetric change of the expansion space and the actual thermophysical properties of the working fluid, helium are considered. The basic equations are mode up of one-dimensional fluid equations and an energy equation of the regenerator material and the cooling stage. The fluid equations are expressed in the general coordinate system of which a coordinate axis moves with time to take account of the volumetric change of the expansion space. These basic equations are differentiated by using the TVD MacCormack method. In order to verify the simulation model, the theoretical validity of the calculation results was checked and calculation results were compared with results of experiments. As a result it was confirmed that the simulation model is appropriate.

We have suggested that non-uniform currents occur due to certain design parameters, for example a combination of cabling pitches, in a previous study. In the present study, we evaluate the occurrences of non-uniform current distributions in terms of design parameters, i.e., the combination of cabling pitches, winding methods (solenoidal and pancake winding) and cross-sectional shape of the cable by numerical analyses. Finally, some basic design concepts to solve this problem are proposed.

This paper describes analysis of transitional change in pressure after a quench of field windings in a superconducting generator. We constructed a calculation model by which it is possible to predict transitional changes in pressure after a quench in the helium vessel of a superconducting generator, and performed numerical calculation. To verify the calculation model, the calculated results were compared with tested results derived from the Model Rotor, and we could confirm the accuracy of the calculation model. Applying the calculation model to the 70-MW class superconducting generator, we found that the maximum pressure in the helium vessel of the 70-MW class superconducting generator reached 1. 7 MPa at the quench of the maximum field current.

This paper describes the numerical simulation of a GM refrigerator operating at about 4K. The simulation model is composed of a regenerator, an expansion space, and a cooling stage. The volumetric change of the expansion space and the actual thermophysical properties of the working fluid, helium are considered. The basic equations are made up of one-dimensional fluid equations and an energy equation of the regenerator material and the cooling stage. The fluid equations are expressed in the general coordinate system of which a coordinate axis moves with time to take account of the volumetric change of the expansion space. These basic equations are differentiated by using the TVD MacCormack method. In order to verify the simulation model, the theoretical validity of the calculation results was checked and calculation results were compared with results of experiments. As a result it was confirmed that the simulation model is appropriate.

Overview Performances of cell stacks are simulated, focusing on driving state of anode system. This simulation technique takes overall transport phenomena in PEFC fuel cell systems, such as transport of gas species and liquid water in both anode and cathode channels and across MEA, thermal balance, electrochemical reactions and current distributions. Injector and exhaust systems are modeled by boundary conditions, mimicking actual driving conditions. Relation between cell performances and driving state of anode system, for example, consumption of hydrogen, build-up of liquid water and cross-over nitrogen and purging by control of injector and/or ejector can be discussed based on simulated results. Over-all performance of anode system is one of crucial issue for durability and cost-reduction of fuel cell systems. These results show good applicability of this kind of simulations on design of PEFC stack system. Numerical Modeling and Results Simulation is performed by our own simulation software for PEFCs, which is capable of simulating full-stack fuel cell system for fuel cell vehicles (up to 400 cells) under transient operating conditions. An important feature of this software is that macroscopic models are applied for microscopic phenomena in the MEA such as electrochemical reactions and proton/water transport. Heat transfer and fluid of liquid-gas two phase fluid with phase changing are also taken into account. These models are coupled with multi-dimensional heat and mass transport equations, including effective parameters for gas diffusivity and permeability in the GDL and equivalent hydraulic diameter in the flow channel. This software can also simulate cathodic degradation by carbon corrosion reactions. Performances of up to 400 cells stacks are simulated. A numerical model of anode system is constructed by adding transient boundary conditions for an injector and an exhaust system with an ejector. These transient boundary conditions represent open / close timings of injector and ejector under actual driving conditions. Distributions and consumptions of hydrogen, build-up of cross-leak nitrogen and condensate liquid water can be shown under constant (up to 30A) loading. Simulated results show difference of cell potential between of stacked cells, and relation between performance distributions and balances of transport phenomena in stack systems. Effects of configuration of stack systems are also shown. Based on these results, design of stack systems and control schemes of anode system can be discussed. Those discussion can provide useful information for improving durability of stacked cells by avoiding depletion of hydrogen, and / or examination of control schemes which can efficiently utilize hydrogen fuel.

The Vuilleumier cryocooler is a heat engine which uses heat energy rather than mechanical energy to cyclically pressurize the working gas. The Vuilleumier cryocooler has the potential advantages of long lifetime and low mechanical vibration. This paper describes the specifications required for the machine, and detailes of design based an isothermal thermodynamic cycle. The analytical model can be used to clarity the working gas behavior in the system and determine the performance characteristics of the machine by calculating all losses to be mutually decoupled. As typical performance values from the calculation, the machine has a cooling capacity of 2.03 watts at 80 K under heater input power of 150 watts, charge pressure of 3 MPa and cycle speed of 4 s-1. The nominal dimensions of the first trial machine are length of 300 mm, width of 150 mm and height of 280 mm. The weight of the complete machine was 6 kg.

Acoustic emission monitoring on a model field winding for the 70 MW class superconducting generator was performed during cooldown, excitation and quenches to diagnose the integrity of the model field winding and improve the reliability of the field windings for the generator. The results confirm that the acoustic emission signals are mainly due to conductor motions which cause premature quenching of the winding. It is therefore important to support the field windings as rigidly as possible to prevent conductor motions and to increase the stability of the field windings.

We are now developing a 70MW class superconducting generator with low response excitation (hereafter we call it simply 70MW class machine). The field windings for the 70MW class machine require high current density to achieve low reactance and low a. c. losses to resist the magnetic flux variation at the power system fault. To develop such field windings with high current density and low a. c. losses, it is important to select proper superconducting cables and to find appropriate cable supporting and cooling system. Therefor we constructed model coils of the field windings for the 70MW class machine and investigated these performance. This paper describes at first the configuration of the model coils and then the test apparatus and the test method for these model coils. This paper also describes the test results and the applicability of these test results to the field windings for the 70MW class machine. We have found the superconducting cable and the cable supporting and cooling system which are applicable to the field windings for the 70MW class machine.

Overview Wet/dry cycling in membrane of a PEFC is simulated under time-dependent load profiles which imitate actual driving conditions. Wet/dry cycling is an important issue to extend durability of PEFCs, since mechanical degradation is more likely to take place where gradation of water content distribution in membrane is large and wet/dry cycling is frequent. Performances of a 30cm times 10cm full cell is simulated, calculating transport of gas species and liquid water coupled with electrochemical reactions and current balances. Load profile is given by time-dependent total current conditions. Based on simulated results, dependence of wet/dry cycling on channel configurations and operating conditions are discussed. Numerical Modeling and Results Simulation is performed by our own simulation software for PEFCs, which is capable of simulating full-stack fuel cell system for fuel cell vehicles (up to 400 cells) under transient operating conditions. An important feature of this software is that macroscopic models are applied for microscopic phenomena in the MEA such as electrochemical reactions and proton/water transport. Heat transfer and fluid of liquid-gas two phase fluid with phase changing are also taken into account. These models are coupled with multi-dimensional heat and mass transport equations, including effective parameters for gas diffusivity and permeability in the GDL and equivalent hydraulic diameter in the flow channel. This software can also simulate cathodic degradation by carbon corrosion reactions. Performance of cell is simulated under assumed load profiles, modeled by transient output current boundary conditions. Typical time-scale and range of supposed current conditions is 1[sec] and0.1-1.0[A/cm2], respectively, which imitates actual driving conditions on urban streets. Stoichiometric ratio and humidity of reactant gas are also changed simultaneously with the load profile. Simulated results show transient behavior of wet/dry cycling. For example, soon after the output current is increased, large difference in reaction current density can be created, depending on the distribution of reactant gas flow. This results in large gradient of water content in membrane, where mechanical degradation is expected depending on flow distributions and operating conditions. In the same way, water content distribution between stacked cells can be simulated. In addition, effect of different time-scales of load profiles and response of water distribution can be discussed. These results can be useful information to consider the possibility of mechanical degradation.