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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.

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.

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.

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.

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.

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.

Overview Polymer Electrolyte Fuel Cell (PEFC) is expected as a new power source in automobiles with high power density and low emission. Although PEFC has many advantages compared with internal combustion engines, the cost reduction and the improvement of performance and durability are needed for its practical application. For improvement of PEFC, it is important to understand the mechanism inside it under various operating and structural conditions and to feedback into the design of membrane electrode assembly (MEA) and bipolar plate constituting fuel cell stack. In order to visualize inside PEFC, we have been developed a numerical simulation tool calculating the cell and stack performance and physical distributions and a nondestructive, real-time/space visualization technique for oxygen partial pressure in the cathode flow channel and the GDL using oxygen-sensitive luminescent dye film [1]. In this study, as for the first step of our numerical modeling development, the effects of operating condition, for example, cathode flow rate on the test cell as well as commercial-sized cell and stack were investigated. Numerical Modeling Inside the fuel cell, multi-physical and multi-scale of phenomena such as multi-component gas, liquid water and heat transport inside the flow channel and the GDL, electrochemical reactions and proton/water transport in the MEA are nonlinearly coupled [2]. These phenomena require too much calculation cost to be solved in high resolution by fully 3-dimensional equations based on computed fluid dynamics (CFD), so it is necessary to apply simplified models. In our modeling, macroscopic models are applied for microscopic phenomena in the catalyst layer and electrolyte such as electrochemical reactions (HOR/ORR) and proton/water transport. And these models are coupled with multi-dimensional heat, gas and liquid water transport equations in which effective parameters such as gas diffusivity and permeability in the GDL and equivalent hydraulic diameter in the flow field of bipolar plate and the manifold of stack are included [3]. Results First of all, the performance of 25cm2test cell with single serpentine flow channel was carried out. Hydrogen and air flow rate is 300ml/min, relative humidity is 60%RH, cell temperature is 353.15K and back pressure is 1atm, respectively. The distribution of oxygen partial pressure in cathode flow channel and on the GDL surface at cathode utilization 80% (0.58 A/cm2) are shown in Figure 1 compared to the measured data by a nondestructive visualization system. The results are good agreement with the measured data and indicate that the numerical prediction of current density distribution is valid in our model. Applying the validated model, the effect of cathode flow rate on the performance of short stack with 20 cells (max. 5kW) was carried out. As for the other operating conditions, relative humidity is 50%RH, cell temperature is 343.15K and back pressure is 1.5atm, respectively. Figure 2 shows the effect of cathode utilization on the distribution of normalized in-flow rate and ORR gain for each cell at 0.5A/cm2. As cathode utilization increases, in-flow rate decreases and ORR gain increases remarkably near the dead end of stack. This is because liquid water accumulates in the flow channel and the GDL. In addition, the performance of full-scale PEFC stack for automobiles under various operating conditions will also be discussed in this meeting. References 1. J. Inukai et al., (Submitted to Physical Chemistry Chemical Physics) 2. C.Y. Wang, Chem. Rev., 104, 4727-4766 (2004). 3. M. Yoneda et al., Proceedings of the ASME 8th Int. Conf. on Fuel Cell Science, Engineering, and Technology, Vol.1, 497-504 (2010)

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It is important for rotors of superconducting generators to maintain a stable flow pattern of liquid helium to prevent an accidental transition of superconducting field windings into the normal state. Liquid helium within the rotating helium pool of superconducting generators has two major flow patterns. One is a gravity dominant flow pattern and the other is a centrifugal force dominant flow pattern. The former has a flat horizontal surface of a liquid, and the latter has a cylindrical one. This paper describes the transition phenomena between these two flow patterns. The results of a visual experiment using water, fron 113 and silicon oil were presented in the first report of this paper. The second report at first describes experimental data of liquid helium obtained using a rotating helium pool, and then compares these experimental data with the results of a visual experiment.