A sequential quadratic programming-based algorithm for optimization of gas networks

British Gas uses a complex, heavily looped network of pipes and controllable units (compressors and regulators) to transmit gas from coastal supply terminals to regional demand points. Computer algorithms are required for efficient management of the system. This paper describes an algorithm for optimal control over periods of up to a day. The problem is large scale and highly nonlinear in both objective function and constraints. The method is based on Sequential Quadratic Programming and takes account of the structure of the pipeflow equations by means of a reduced gradient technique which eliminates most of the variables from the quadratic subproblems. The latter involve only simple bound constraints, which are handled efficiently by a conjugate gradient-active set algorithm. Trust region techniques permit use of the exact Hessian, preserving sparsity. More general constraints are handled at an outer level by a truncated augmented Lagrangian method. Results are included for some realistic problems. The algorithm is generally applicable to problems with a control structure.     

Two cooperatively social populations of the theridiid spider Anelosimus studiosus in a temperate region

The quality of an individual's odour can allow potential mates to discriminate against individuals of low social class, poor health status or unsuitable genotype. Competitive scent marking provides a further mechanism which could allow mates to discriminate between individuals of apparently high quality. The presence or absence of fresh countermarks from competitors within an owner's territory or area marked by a dominant animal provides a reliable indicator of the owner's ability to defend its territory or dominate competitors. This could be used by potential mates to discriminate between individuals advertising their apparently high competitive ability through their scent-marking behaviour and odour quality. We tested this by manipulating scent marks in the neighbouring territories of wild-caught male house mice, Mus domesticus. As predicted, oestrous females used scent marks to select males apparently able to defend exclusive territories over those unable to exclude intruders. Females were more strongly attracted to the odour of owners of exclusively marked territories and showed more sexually related behaviour when interacting with these males. Furthermore, while females preferred a territory containing a better protected nest site regardless of the owner's apparent competitive ability, they still used the presence or absence of intruder countermarks when selecting a potential mate. This suggests that females use scent marks as a reliable signal of the best-quality mate among neighbouring males independently of their nest location. Since assessment depends on both the territory holder's own marks and those of competitor males, countermarking is likely to be an important mechanism of competition for mates between neighbours. Copyright 1998 The Association for the Study of Animal Behaviour     

Pinpointing users with location estimation techniques and Wi‐Fi hotspot technology

Location awareness is becoming an important capability for mobile computing; however, it has not been possible until now to provide cheap pervasive positioning systems. Wide area coverage is most famously achieved by using global positioning systems (GPS). A constellation of low‐orbit satellites cover the earth's surface. Unfortunately GPS does not work indoors and has limited success in big cities because of the ‘urban canyon’ effect. PlaceLab is a research project that attempts to solve the ubiquity issues surrounding 802.11‐based location estimation. PlaceLab, like RADAR, uses a device's 802.11 interface; however, it does not require the area to be pre‐calibrated. It predicts location via the known positions of the access points detected by the device. Commonly used systems have a number of drawbacks, including cost, accuracy and the ability to work indoors. PlaceLab is a piece of open source software developed by Intel Research that can pinpoint a user within a Wi‐Fi network. We set out here to investigate whether PlaceLab can be used as a means of establishing a user's position. This type of investigation could, if successful, pave the way for the development of other location‐based applications. This report documents the efforts to answer the above question. PlaceLab was found to work, but only in ideal locations where factors such as the number of floors and the lack of available APs did not affect its use. It was concluded that these factors prevent the system from being effective as a means of establishing a user's position in most locations on campus. Copyright © 2008 John Wiley & Sons, Ltd.     

3D Metal printed heat sinks with longitudinally varying lattice structure sizes using direct metal laser sintering

This research relates to the design, modelling and fabrication of 3D metal printed heat sinks. The heat sinks presented in the research are the commonly used longitudinal fin solid heat sink (LFSHS) and three LFSHS lattice structure designs, differing only in their lattice sizes, fabricated using the Direct Metal Laser Sintering (DMLS) technique in Maraging Steel (MS1), on an EOSINT M280 system. In order to increase the heat sink surface area, the heat sinks are manufactured with mesh lattices along the length of the fins, while keeping the overall heat sink volume constant. The research is focused on pushing the limitations of the DMLS technique for the development of repeating unit, lattice structures heat sinks, and to examine the effect of incrementally varying the lattice sizes with regards to the resultant surface area of the heat sink and the thermal performance of the system. The results obtained under natural convection show that the thermal performance of the LFSHS outperformed all lattice structure heat sinks. This is due to the fact that, the pressure drop across the lattice heat sinks were so high, due to lattice meshes that it negated the positive effect of the greater surface area.     

Organic photovoltaics using thin gold film as an alternative anode to indium tin oxide

Indium Tin Oxide (ITO) is the most commonly used anode as a transparent electrode and more recently as an anode for organic photovoltaics (OPVs). However, there are significant drawbacks in using ITO which include high material costs, mechanical instability including brittleness and poor electrical properties which limit its use in low-cost flexible devices. We present initial results of poly(3-hexylthiophene): phenyl-C₆₁-butyric acid methyl ester OPVs showing that an efficiency of 1.9% (short-circuit current 7.01 mA/cm², open-circuit voltage 0.55 V, fill factor 0.49) can be attained using an ultra thin film of gold coated glass as the device anode. The initial I-V characteristics demonstrate that using high work function metals when the thin film is kept ultra thin can be used as a replacement to ITO due to their greater stability and better morphological control.     

Determining Intent — Opportunistic vs Targeted Attacks

To assess the importance and potential impact of an incident accurately computer security professionals need to understand an offender’s criminal skill, knowledge of targets, and intent. A thief who selects targets of opportunity based on insecure systems presents a significantly different threat than an individual who targets a specific organization to obtain specific information. This article compares two intellectual property theft cases to provide readers with practical investigative insights, noting costly mistakes and pointing out behaviour reflected in digital evidence. Although these cases are based on actual investigations, they have been modified to protect the innocent.     

The formation of polymeric films directly on rubbing surfaces to reduce wear

A new concept—the reduction of wear by the use of particular compounds capable of forming protective polymeric films directly on rubbing surfaces—is presented; and the idea is supported by experimental data obtained in high contact stress systems with a variety of compounds. In addition, this idea has led to the development of several new and potent additives for reducing wear and scuffing.According to this concept, the potential polymer-forming compound (or compounds) is dissolved or mixed at low concentrations in a carrier (e.g., a liquid hydrocarbon). Due to the high surface temperatures in regions of greatest contact and possibly to the added catalytic action of certain freshly exposed surfaces, very thin protective polymeric films will form in these areas. The first step may involve concentration of the polymer-former on the solid surface by adsorption. In a dynamic system, the polymer films are continually being formed and worn away. However, the system tends to have a built-in control; the very formation of the polymer film will tend to reduce contact and friction and therefore the rate at which the film continues to form. As the polymer film is physically worn away, friction and surface temperatures will tend to increase, thereby causing the rate of film formation to increase.The interposed film is a deposited one and may be relatively thick.Its basic function is to reduce contact and adhesion between solids.Evidence in support of the in situ polymer film mechanism includes (a) the superiority of polymer-forming compounds over closely-related non polymer-formers in a variety of boundary lubrication tests, (b) indications of localized and adherent surface films, (c) the existence and solvent removal behavior of pronounced beneficial carryover effects, (d) the results of mechanism studies in a dynamic sliding system with radioactively-labeled compounds, and (e) the overall success of the approach in developing new classes of effective additives for reducing wear, scuffing, and surface damage.An outstanding example of the application of this concept to a real problem was demonstrated by the striking effectiveness of partial (e.g., mono-) esters made by reacting long-chain C₃₆ dimer acids with glycols (e.g., ethylene glycol). These compounds are believed to act by the formation of polyester films as follows: HOOC-R-COO-C₂H₄OH→

HO[-OC-R-COO-C₂H₄O] H + H₂O↑It was found that useful polymer-formers may be of the condensation type (e.g., to form polyesters, polyamides) or of the addition type; but the condensation or step-reaction approach appears to be more effective in the systems investigated. The picture is complex, however, and not all polymer-formers function. Possible reasons for this are discussed.     

Neonatal sex hormones have 'organizational' effects on the hypothalamic-pituitary-adrenal axis of male rats

Sex hormones have activational effects on the hypothalamic-pituitary-adrenal (HPA) axis in adulthood: For example, corticosterone release is influenced by gonadal status. These experiments investigated whether sex hormones have organizational effects on the HPA axis of male rats: Do sex hormones have relatively permanent effects on its development? In adults, both neonatal (neoGDX) and adult gonadectomy (adult GDX) resulted in elevated corticosterone (CORT) levels in response to stress compared to intact rats. Five days of testosterone propionate (TP) replacement was not as effective at attenuating CORT levels in neoGDX rats as in adult GDX rats. Neonatal GDX elevated corticosterone binding globulin (CBG) levels, whereas adult GDX was without effect. In Experiment 2 the effects of neonatal gonadectomy and neonatal treatment with either TP, estradiol benzoate (EB), or oil vehicle was examined. Despite 14 days of hormone replacement, neoGDX showed elevated CORT levels in response to stress compared to all other groups. A single neonatal dose of TP or EB in neoGDX rats eliminated the increased responsiveness. Neonatal TP and EB were without effect in sham-operated rats. Plasma CBG levels were elevated in neoGDX groups regardless of neonatal hormone treatment. Corticosteroid receptor binding levels were examined in various brain areas and the pituitary in two groups most different in their androgen experience: NeoGDX and shams that did not receive treatments as adults. NeoGDX had lower levels of glucocorticoid receptor, and higher levels of mineralocorticoid receptor binding in the pituitary. No other receptor differences were found. These experiments suggest that neonatal sex hormones influence the sensitivity of the HPA axis to sex hormones in adulthood and, thus, that they have organizational effects in addition to activational effects on HPA function.     

The Visible Spectra of Some 1,4-Diaminoanthraquinone Disperse Dyes in Solvents and on Polymer Substrates

The visible spectra of a series of 1,4-disubstituted aminoanthraquinone dyes dissolved in different solvents and polymer substrates have been measured. The position of the absorption maximum has been correlated with a weighted mean ionization potential of the substituent groups. Solvent shifts were found to be small but the dependence on polarity and hydrogen-bonding ability was shown to act in opposite directions. A detailed examination of the characteristic double-peak structure of the visible-absorption band has shown that the splitting is due to vibrational effects. The variation in the absorbance ratio of the two peaks with substituent and solvent has been explained in terms of the relative disposition of the ground- and excited-state potential- energy curves. The effect of concentration on the double-peak ratio has been re-examined and found to be negligible.     

Evaluation of layout and atmospheric stability effects in wind farms using large‐eddy simulation

Large‐eddy simulation (LES) has been used previously to study the effect of either configuration or atmospheric stability on the power generated by large wind farms. This is the first study to consider both stability and wind farm configuration simultaneously and methodically with LES. Two prevailing wind directions, two layouts (turbines aligned versus staggered with respect to the wind) and three stabilities (neutral and moderately unstable and stable) were evaluated. Compared with neutral conditions, unstable conditions led to reduced wake losses in one configuration, to enhanced wake losses in two and to unchanged wake losses in one configuration. Conversely, stable conditions led to increased wake losses in one, decreased wake losses in two and unchanged wake losses in one configuration. Three competing effects, namely, rates of wake recovery due to vertical mixing, horizontal spread of wakes and localized regions of acceleration caused by multiple upstream wakes, were identified as being responsible for the observed trends in wake losses. The detailed flow features responsible for these non‐linear interactions could only be resolved by the LES. Existing analytical models ignore stability and non‐linear configuration effects, which therefore need to be incorporated. Copyright © 2017 John Wiley & Sons, Ltd.