A reappraisal of insect flight towards a distant point source of wind-borne odor

This communication reappraises the behavioral evidence concerning insect flight toward a point source of wind-borne odor in the light of meteorological information not yet considered in this context. The horizontal tracks of puffs of smoke from a generator in the open air were videorecorded and found to continue along nearly straight lines from the source for at least 25 m, while the shifting wind direction caused the plume formed by the succession of puffs to snake to and fro. It is inferred from this and much previous work that within such a distance the wind will be aligned on the source of any wind-borne odor wherever the odor can be detected. This being so, a strategy of finding the odor source by flying roughly upwind on meeting the odor, but holding station against the wind with or without casting across it on losing the odor (odor-modulated anemotaxis), seems likely to be highly adaptive, whereas a strategy of flying along the plume (odor-trail following) seems unlikely since it would often take the flier in wrong directions and would be more disrupted by turbulence.     

Optimal search direction for an animal flying or swimming in a wind or current

The problem of the optimal direction in which a flying or swimming animal should search for a chemical plume was addressed. Active spaces were approximated by sphere, prolate ellipsoids, or rectangular parallelepipeds of various length-to-width ratios. The optimum course direction for the sphere was in the direction of flow (downwind). For active spaces that were highly elongated along the direction of the wind or current, the optimal course heading (with respect to the moving medium) was nearly across the flow. For intermediate shapes, the optimal course was intermediate. Because of the effect of the moving medium, these course headings resulted in actual ground tracks that were more in the direction of the flow, depending on the relative speeds of flying (swimming) and the wind (current). When the two speeds were equal, the magnitude of the advantage of choosing the optimum direction over a random direction was close to 50% with a small dependence on the shape of the active space. If the active space was spherical or highly elongated or locomotor speed was much greater than the speed of the current, the advantage approached a factor of /2 ( 1.57).     

Chemical orientation of lobsters,homarus americanus,in turbulent odor plumes

The lobster,Homarus americanus, relies upon its lateral antennules to make initial directional choices in a turbulent odor plume. To determine whether chemical signals provide cues for source direction and distance during orientation, we studied the search patterns of the lobster orienting within a turbulent odor plume. In an odor plume, animals walked significantly more slowly and most often up the middle of the tank; control animals (no odor present) walked rapidly in straight lines, frequently along a wall. Search patterns were not stereotyped either for the population of experimental animals or for individuals. Three different phases of orientation were evident: an initial stage during which the animals increased their walking speeds and decreased their heading angles; an intermediate stage where both the walking speed and headings were constant; and the final stage close to the source, where heading angles increased while walking speed decreased. During this last stage the animals appear to be switching from a distance orientation (mediated by the antennules) to a local food search (mediated by the walking legs) as evidenced by a great increase in leg-raking behavior.     

非平衡等离子体脱臭技术研究进展

提出了一种新型的恶臭治理技术—非平衡等离子体,简要介绍了该技术的基本原理、在恶臭废气治理方面国内外研究进展及存在问题与研究思路等,最后对恶臭治理工业应用的前景进行了展望。     

Experimental study of fire growth and ejected plume in a cross‐ventilation compartment under wind condition

In this study, a set of reduced‐scale experiments were conducted to study the influence of external wind on the fire growth and ejected plume in a compartment with two openings. The approaching wind velocity was set as 1.5 and 3.0 m/s, respectively. The temperatures in the fire compartment were also measured by thermocouple matrixes. The images of the projected flames from the opening and the fuel mass loss rate were recorded by digital video and electronic balance, respectively. It is observed that the wind with velocity of 1.5 m/s can reduce the combustion severity by decreasing the ventilation in the fire room and enhance the duration time of combustion. On the contrary, the wind with velocity of 3 m/s can promote the combustion severity by increasing the ventilation in the fire room and reduce the duration time of combustion. The theoretical analysis shows how the external wind that coupled with the thermal buoyance influence the ventilation of the compartment, and a critical velocity or a dimensional number are suggested to predict the ventilation of the fire room, which is believed to influence the compartment fire behavior greatly.     

The organized flow structure of an oscillating bubble plume

The detailed experimental investigation of an oscillating bubble plume created in a quasi-two-dimensional bubble column is reported for low void fraction and millimeter bubbles. The plume exhibits periodic oscillations and generates large-scale coherent structures in the liquid. The local and transient hydrodynamics of this bubbly flow was investigated with particle-image velocimetry (PIV) in the liquid phase and via optical fiber probe and the shadowgraph technique in the gas phase. First, long time averaging is performed (over a large number of plume oscillation periods). Thus, horizontal profiles of gas fraction and of horizontal and vertical components of mean and root mean square velocities in both phases can be examined. Then fluctuations of liquid velocities are studied, in terms of probability density function (indicating organized and random fluctuations), and in terms of phase-averaged components. Finally, proper orthogonal decomposition is applied to PIV data to extract coherent structure contributions more efficiently.     

Research on the plume shape under optimal wind environment to prevent the smoke backflow and combustion gains in utility tunnel

The utility tunnels have been applied extensively to run the various pipelines in the urban areas such as the gas pipeline, electrical power cables, and the likes. Contradicting with the rapid development of the utility tunnels is the ambiguity of the fire protection code to which one critical point is whether to ventilate in the fire accident, which is hampered by the effect of wind on the combustion gain. Therefore, this paper combines the plume function with the backlayering length and critical backflow velocity to explore the plume shape, optimize the ventilation environment, and decrease its combustion gain in which shows three key features that include the concavity and convexity characteristics, instability of plume, and the balance feature. Moreover, through their derived five plume shape constraints, we acquire the optimal wind environment. Furthermore, we found that the expected length is 0.12 in optimal condition when the original critical velocity is larger than 0.43, and the other cases are 0.05 for expected length. Meanwhile, the ventilation velocity needs to be increased three to seven times. The study provides new insight into the plume flow under the wind environment and would accelerate the formalization of fire protection design for utility tunnel.     

硫化氢恶臭气体吸收液的电化学氧化处理过程

利用单槽无隔膜电化学反应器,研究了硫化氢恶臭气体碱性吸收液在圆形平板钌钛DSA电极上的电化学氧化处理过程,考察了电流密度、初始料液浓度、辅助电解质以及pH值对S2?电解去除效果的影响。结果表明：在电流密度25 mA/cm2、S2?初始浓度23 mmol/L时,S2?去除率可达95%以上;S2?的氧化产物主要为SO42?,约占总反应产物的95%,而硫单质占2%～3%,同时生成少量SO32?、S2O32?;S2?去除速率受到S2?浓度的较大影响,电流密度越高去除速率越快;pH值影响Sx2?的形成,强碱条件可避免阳极钝化;与NaCl等辅助电解质相比,NaOH最有利于提高电解氧化的速度和深度,S2?去除率达90%时,可缩短处理时间近40%。     

Quantitative analysis of the effects of ultrasound from an odor sprayer on moth flight behavior

A piezoelectric sprayer was recently developed for precision release of odor stimuli in olfactory research. The device replaces conventional dispensers used to release semiochemicals in studies of moth flight toward odor sources. However, the device generates high-frequency sounds in the range that some moths can hear. Ultrasound from the standard set-up sprayer had a considerable impact on flight behavior of the silver Y moth, Autographa gamma, tested in a flight tunnel. It was affected at all behavioral stages when the dispenser was driven at 120 kHz. Only 5% of the moths reached the source when exposed to 120-kHz sound from the dispenser compared to 65% in the control group without sound. The proportion taking flight was also reduced. Hearing threshold curves obtained electrophysiologically revealed that moths were sensitive to the frequency range at which the sprayer was operated and that sound intensity from the sprayer was up to 40 dB above the moths' electrophysiological hearing threshold. The audiogram for A. gamma was similar to audiograms obtained for other noctuids. Hearing sensitivity was highest at around 15 kHz, where the threshold was 35 dB SPL (sound pressure level). The threshold increased with frequency up to 94 dB SPL at 160 kHz. We improved the sprayer to operate at 300 kHz, which is beyond the hearing ability of most insects with ears. At this high frequency, the moths' sensitivity to ultrasound is reduced considerably, and we did not observe any effect on flight behavior compared to a control group without sound. Accordingly, this new piezoelectric sprayer can be used with ultrasound-sensitive insects and insensitive insects alike.     

An investigation of human apocrine gland secretion for axillary odor precursors

Recently completed studies from our laboratories have demonstrated that the characteristic human male axillary odors consist of C₆ to C₁₁ normal, branched, and unsaturated aliphatic acids, with (E)-3-methyl-2-hexenoic acid being the most abundant. To investigate the mechanism by which the odor is formed, it is necessary to determine the nature of the odorless precursor(s) found in the apocrine secretion which is converted by the cutaneous microorganisms to the characteristic axillary odor. Pooled apocrine secretion was obtained from several male volunteers by intracutaneous injection of epinephrine. Partitioning this secretion into aqueous and organic soluble fractions was followed by hydrolysis of each fraction with NaOH or incubation with axillary microorganisms (cutaneous lipophilic corynebacterium). Analysis by gas chromatography/mass spectrometry (GC/MS) revealed the presence of (E)- and (Z)-3-methyl-2-hexenoic acid in the aqueous phase hydrolysate and aqueous phase incubated with bacteria; however, only a trace amount was seen in the resultant organic phase mixtures. These results suggest that a water-soluble precursor(s) is converted by the axillary flora to the characteristic axillary odors.     

Habitat-specific Signal Structure for Olfaction: An Example from Artificial Streams

Many animals use chemical signals to acquire information about their habitats. The structure of this information is dependent upon specific features within a habitat, and the information in signals can be habitat-specific. We quantified the spatial and temporal information in an aquatic odor plume in three different artificial stream habitats with different substrate types by measuring turbulent odor plumes with an electrochemical detection system. Streams had one of three substrate types that correlated with typical aquatic habitats: sand (4.2 × 10^–2 cm diameter), gravel (2.5 cm), and cobble (4.5 cm). As predicted from the hydrodynamics, the spatial and temporal structures of the signals were different on different substrates. Spectral analysis showed that the sand and cobble substrates had signals that were dominated by lower frequency fluctuations, whereas gravel had the highest and broadest range of signal fluctuations. Cross- and autocorrelations showed that signals on the gravel substrate had the largest spatial and shortest temporal components. Our results imply that the information obtained from chemical signals may be limited in some habitats. These constraints on information may affect how organisms perform chemically mediated behaviors.     

A colorizer for use in determining an optimal ophthalmic tint

A colorizer for use in the provision of an ophthalmic tint is described. The design differs from that of an earlier model in that the spectral power distribution of the light in the instrument is very similar to the spectral power distribution obtained when tinted glasses are worn under typical lighting. The similarity in spectral power is obtained notwithstanding the fact that the instrument uses an additive mixture of filtered light, whereas tinted lenses use a subtractive mixture of dyes. The precision of color selection is high, and this precision is shown to be necessary to optimize reading fluency. Because of the similarity in spectral power distribution, it is possible to examine the effect of ophthalmic tints not only on reading fluency, but also on the perception and naming of colored surfaces, and the examination can be undertaken by patients who have color vision anomalies. Compared with the earlier design, the use of a diffuse source and seven colored filters reduces the requirement for precision in alignment of components; the variation in color from one instrument to another is, therefore, small, allowing a single calibration for all instruments. This calibration permits the matching of colored ophthalmic lenses to a given colorizer setting, using a computer algorithm which enables practitioners with color vision deficiencies to undertake ophthalmic colorimetry. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 246–253, 2001     

Nonequilibrium thermodynamics for multiphase reacting systems: an optimal control approach

This paper sets optimal control framework for balance and kinetic equations of multiphase reacting systems consistently with the second law of thermodynamics. Approaches effective in contemporary theory of nonequilibrium thermodynamics of single-phase systems are here extended to include interfacial discontinuities, surface reactions and interface transports which are phenomena typical of multiphase systems. We arrive at Lagrangian and Hamiltonian structures of transport equations and laws of chemical kinetics, which constitute efficient forms serving to generalize linear models to nonlinear regimes. Local disequilibria are predicted which are shown to be responsible for onset of interfacial and bulk instabilities.     

A systematic methodology for optimal mixture design in an integrated biorefinery

Biomass is a sustainable source of energy which can be utilised to produce value-added products such as biochemical products and biomaterials. In order to produce a sustainable supply of such value-added products, an integrated biorefinery is required. An integrated biorefinery is a processing facility that integrates multiple biomass conversion pathways to produce value-added products. To date, various biomass conversion pathways are available to convert biomass into a wide range of products. Due to the large number of available pathways, various systematic screening tools have been developed to address the process design aspect of an integrated biorefinery. Process design however, is often inter-linked with product design as it is important to identify the optimal molecule (based on desired product properties) prior to designing its optimal production routes. In cases where the desired product properties cannot be met by a single component chemical product, a mixture of chemicals would be required. In this respect, product and process design decisions would be a challenging task for an integrated biorefinery. In this work, a novel two-stage optimisation approach is developed to identify the optimal conversion pathways in an integrated biorefinery to convert biomass into the optimal mixtures in terms of target product properties. In the first stage, the optimal mixture is designed via computer-aided molecular design (CAMD) technique. CAMD technique is a reverse engineering approach which predicts the molecules with optimal properties using property prediction models. Different classes of property models such as group contribution (GC) models and quantitative structure property relationship (QSPR) are adapted in this work. The main component of the mixture is first determined from the target product properties. This is followed by the identifying of additive components to form an optimal mixture with the main component based on the desired product properties. Once the optimal mixture is determined, the second stage identifies the optimal conversion pathways via superstructural mathematical optimisation approach. With such approach, the optimal conversion pathways can be determined based on different optimisation objectives (e.g. highest product yield, lowest environmental impact etc.). To illustrate the proposed methodology, a case study on the design of fuel additives as a mixture of different molecules from palm-based biomass is presented. With the developed methodology, optimal fuel additives are designed based on optimal target properties. Once the optimal fuel additives are designed, the optimal conversion pathways in terms of highest product yield and economic performance that convert biomass into the optimal fuel additives are identified.     

A simple numerical approach for the optimal design of an extrusion die

A simple numerical approach that is based on the lubrication approximation is developed for the optimal design of a linearly tapered coat-hanger die. This approach does not require the analytic pressure drop / flow rate equations for flow in the manifold and in the slot section, therefore any generalized Newtonian fluid model can be easily incorporated. Example calculations have demonstrated that the predictions based on this approach are reasonably accurate as compared with those from the complete 3-D finite element simulations.     

Trade-off optimal design of a biocompatible solvent for an extractive fermentation process

In this study, crisp and flexible optimization approaches are, respectively, introduced to design an optimal biocompatible solvent for an extractive fermentation process. The optimal design problem is formulated as a mixed-integer nonlinear programming model in which performance requirements of the compounds are reflected in the objective and the constraints. In general, the requirements for the objective and constraints are not rigid; consequently, the flexible or fuzzy optimization approach is applied to soften the rigid requirement for maximization of the extraction efficiency and to consider the mass flow rate and biocompatibility of solvent as the softened inequality constraints to the solvent design problem. Having elicited the membership function for the objective function and the constraint, the optimal solvent design problem can be formulated as a flexible goal attainment problem. Mixed-integer hybrid differential evolution is applied to solve the problem in order to find a satisfactory design.     

Interactions between pheromone traps with different strength lures for the pine beauty moth,Panolis flammea (Lepidoptera: Noctuidae)

Catches of malePanolis flammea in traps baited with lures containing 25 g of sex attractant are enhanced when in the proximity of traps baited with 125-g lures. The degree of enhancement is increased as the intertrap distance is decreased, and when the low-dose trap is upwind of the high-dose one. The patterns of alteration in trap catch suggest that moths initially attracted by one lure may divert into other traps, which may be either upwind of the original trap (overshooting), or downwind (undershooting). Overshooting can result in up to fivefold increases in catch and may provide a useful method for estimating the attractant zone of particular lure/trap combinations.     

Mixed integer optimal control of an intermittently aerated sequencing batch reactor for wastewater treatment

Optimal aeration control strategies for sequencing batch reactors in WWT with bypass nitrification are hereby studied. The operation is defined alternating aerobic and anoxic phases with high frequency. The controlled variable, the aeration, can only adopt fixed values, on and off, leading to a discrete trajectory of bang–bang type. The problem is to compute the number of switches and individual length of each aerobic and anoxic stage. This leads to a mixed integer nonlinear optimal control problem (MINTOC). The solution is challenging, since both integer and continuous variables ought to be considered in the optimization. In contrast to previous work, where optimization is performed based on the separation and independent solution of the integer and continuous problem, we apply an algorithm originally proposed by Sager (2005). The optimization program minimizes operation time and energy consumption. Effluent concentrations are considered as nonlinear constraints in accordance to environmental regulations.