Solar control coatings, required for architectural glazing applications in warm climates, must provide controlled optical transmission ( approximately 10-50%) of the solar radiation in the visible region and should reflect efficiently in the infrared (>0.7 mu m) region to create a cool interior in the buildings. Thin films of PbS and CuxS on glass substrates, deposited from chemical baths, are shown to possess excellent solar control characteristics-superior or comparable to the metallic solar control coatings. For example, for an acceptable range of integrated optical transmittance ( approximately 10-20%) in the visible region, the integrated infrared reflectance for AM2 solar spectrum for the different glazings are: PbS coated glass, 50%; CuxS coated glass, 14%; stainless steel/Cu coated glass, 25% and tinted glass, 4%. The CuxS and PbS coatings also have the advantage of giving pleasant reflected colours (golden, purple, blue, etc), which improves the cosmetic appearance. This paper presents the basic requirements of solar control coatings and provides a comparison of the characteristics of PbS and CuxS coatings against commercially available coatings.

Purpose-The purpose of this article is to describe multi-tasking behaviour in the workplace; to link its cause to the increasing prevalence of low-cost information and communications technologies and to the changing organizational structures that have evolved to meet the demands and opportunities of these technologies. Design/methodology/approach-This article is a presentation of the current literature on multi-tasking behaviour among knowledge workers with a selective bibliography addressing empirical research into the behavioural, managerial and technological aspects of this phenomenon. It then expands to comprehensive coverage of the literature on past and current thinking about task structuring, strategies for coping in a multi-tasking environment and the changing nature of work and organizations, which fuels the need to multi-task in response to these changes. Findings-Among knowledge workers, multi-tasking behaviour appears to be an inevitable consequence of the presence of increasingly easy access to information. Despite the detrimental effect that multi-tasking has on specific task completion, the paradox is that this does not seem to have an effect on overall organizational productivity. For the USA at least, an average 4 per cent growth rate over the past several years of the late twentieth and early twenty-first centuries shows that productivity has increased in tandem with an increase in multi-tasking behaviour and information technologies. Practical implications-Multi-tasking behaviour needs to be understood in the context of its manifestation as a variable that is at least partially dependent on the existence of relatively "cheap" information. In essence, in an information economy, task completion by knowledge workers to a set deadline may be counterproductive to the interests of the organization as a whole. This article describes certain strategies that can be used to minimize the harmful aspects of continuous task switching and to maximize the returns to experience that multi-tasking can bring to an organization. Originality/value-Multi-tasking behaviour and its link to complexity theory may lead to a new understanding of organizations as highly fluid and variable entities that are impossible to design or maintain centrally and yet whose goals lead to the moment by moment creation of micro-organizational structures that accomplish tasks in a manner that engages the full resources of knowledge workers.

CuxS thin films appropriate for use as solar control coatings for architectural glazing applications have been deposited from chemical baths constituted from copper(II) nitrate or chloride, NH3(aq), NaOH, triethanolamine and thiourea. At ambient temperature (25 degrees C), the duration of deposition ranges from 2 to 12 h, but at 50 degrees C, deposition can be considerably faster, from 1 h to 2 h 50 min. CuxS films deposited in this manner require air annealing at 150 degrees C for about 10 min, to reduce the integrated infrared transmittance, T*(IR), to about 10%. The corresponding integrated transmittance in the visible region, T*(vis), is about 30% and the integrated transmittance for AM2 solar spectra is about 20%. The optical transmittance spectra of the annealed films are peaked in the 0.55-0.575 mu m wavelength range, which provides a greenish yellow illumination inside the building under daylight, that corresponds to the peak in the spectral sensitivity curve of the human eye for photopic (daylight) vision. The reduction in sheet resistance of the CuxS films with the air annealing, from about M Omega Square Operator -1 to about 10-100 Omega Square Operator -1, ensures a low thermal emittance which is a requirement for high-efficiency solar control coatings. The issues involved in the optimization of the deposition conditions for large-area production of the coatings and the choice of protective polymer coatings are also discussed.

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Abstract-This paper presents a new control strategy for power factor correctors (PFCs) used to drive high-brightness lightemitting diodes (HB-LEDs). This control strategy is extremely simple and is based on the use of standard peak-current-mode integrated controllers (PCMICs), reducing its cost and complexity in comparison to traditional PFC controllers. In fact, this method is an alternative implementation of the one-cycle control to PFCs belonging to the flyback family of converters, without introducing high complexity for reducing the total harmonic distortion. In this case, the use of a simple exponential compensation ramp instead of a linear one is the proposed solution for drawing a sinusoidal input current. Moreover, the line current is cycle-by-cycle controlled, and therefore, the input-current feedback loop is extremely fast, which allows the use of this type of control with high-frequency lines. The proposed idea is to apply this simple control to a one-stage PFC in order to design a low-cost ac-dc HB-LED driver. However, the application of this control strategy to PFC belonging to the flyback family of converters is not obvious. Designoriented considerations about its implementation in PCMIC will be provided. Finally, an experimental prototype of this driver was developed.