Uniform sampling of periodic signals using successive conversions

This paper presents a new approach to the generation of uniform sampling signals which is based on multiple signal conversions: from pulse to digital, then from digital to analog and afterwards from analog back to pulse. It is shown that a conventional analog-to-frequency converter is suitable to be used as a controllable pulse generator providing for equidistant sampling pulses the frequency of which is proportional to the sampled signal frequency. This paper describes two methods for designing fast response, jitter-free sampling-time generators allowing accurate, uniform sampling of periodic signals. The prototypes have been built and tested     

An experimental and kinetic modeling study of cyclopentadiene pyrolysis: First growth of polycyclic aromatic hydrocarbons

The importance of 1,3-cyclopentadiene (CPD) and cyclopentadienyl (CPDyl) moieties in the growth of polycyclic aromatic hydrocarbons (PAHs) was studied using new experimental data and ab initio calculations. The experimental investigation was performed in a tubular continuous flow pyrolysis reactor under both high (24molN₂/molCPD)$(24{\text{mol}}_{{\text{N}}_2}/{\text{mol}}_{\text{CPD}})$ and low (5molN₂/molCPD)$(5{\text{mol}}_{{\text{N}}_2}/{\text{mol}}_{\text{CPD}})$ nitrogen dilutions, covering a temperature range of 873–1123 K, at a fixed pressure of 1.7 bara. At the most severe conditions up to 84% of CPD is converted, and the amount of PAHs is more than 65 wt%. Major products observed during CPD pyrolysis were benzene, indene, methyl-indenes and naphthalene, in line with previous studies. On-line GC × GC-FID/(TOF-MS) also allowed to quantify minor species (methane, toluene, styrene, phenanthrene, anthracene, etc.), never reported before at this level of accuracy. The new experimental data have been used to further analyze the role of the successive interactions of CPD, indene, and naphthalene as well as the recombination and addition reactions of their resonantly stabilized radicals and refine their kinetics. The results of the modeling study are in good agreement with existing and new experimental observations.     

New method for reactive power and energy measurement

The properties of an electronic reactive power and energy measurement method based on a frequency-controlled power-to-pulse-rate conversion are analyzed. The reactive power and energy measurements can be efficiently performed by using a simple integrating circuit as a phase shifter, and frequency-controlled analog-to-pulse-rate converter. A low value of the output pulse rate should not be considered as an inherent disadvantage of the method. By introducing a phase-locked loop in order to achieve high pulse-rate output, the benefit of high resolution is added to the method. The improved electronic structure for the measurement can be implemented in the design of reactive power and energy standards. For precision var-hour meters based on the proposed method, it is possible to have an efficient error-checking and adjustment procedure. The proposed method allows reactive power and energy measurement to be made in single- and poly-phase, symmetrical and unsymmetrical, and balanced and unbalanced networks     

Importance of the color of light for the illumination of urban squares

The objective of this article was to establish the significance of parameters relevant for urban square illumination, particularly those related with the color of light. Performed using a questionnaire and with 154 architecture students as respondents, the survey showed that the 18 parameters can be divided into two groups. The first group of 13 parameters refers to the overall impression, influencing the basic and most important lighting aims like safety, security, orientation, visual comfort, and amenity, whereas the second group includes parameters related to lighting features which may negatively influence the overall impression. The four parameters directly linked to the color of light were evaluated lower than expected, indicating that architecture students were probably translating their attitude toward color in architecture to color of light, thus underestimating this lighting parameter. The survey results also showed that female respondents are more sensitive to parameters, which affect safety and security.     

Texture profile analysis of bioadhesive polymeric semisolids: Mechanical characterization and investigation of interactions between formulation components

This study reports the use of texture profile analysis (TPA) to mechanically characterize polymeric, pharmaceutical semisolids containing at least one bioadhesive polymer and to determine interactions between formulation components. The hardness, adhesiveness, force per unit time required for compression (compressibility), and elasticity of polymeric, pharmaceutical semisolids containing polycarbophil (1 or 5% w/w), polyvinylpyrrolidone (3 or 5% w/w), and hydroxyethylcellulose (3, 5, or 10% w/w) in phosphate buffer (pH 6.8) were determined using a texture analyzer in the TPA mode (compression depth 15 mm, compression rate 8 mm s⁻¹, 15 s delay period). Increasing concentrations of polycarbophil, polyvinylpyrrolidone, and hydroxyethylcellulose significantly increased product hardness, adhesiveness, and compressibility but decreased product elasticity. Statistically, interactions between polymeric formulation components were observed within the experimental design and were probably due to relative differences in the physical states of polyvinylpyrrolidone and polycarbophil in the formulations, i.e., dispersed/dissolved and unswollen/swollen, respectively. Increased product hardness and compressibility were possibly due to the effects of hydroxyethylcellulose, polyvinylpyrrolidone, and polycarbophil on the viscosity of the formulations. Increased adhesiveness was related to the concentration and, more importantly, to the physical state of polycarbophil. Decreased product elasticity was due to the increased semisolid nature of the product. TPA is a rapid, straightforward analytical technique that may be applied to the mechanical characterization of polymeric, pharmaceutical semisolids. It provides a convenient means to rapidly identify physicochemical interactions between formulation components. © 1996 John Wiley & Sons, Inc.     

Renewable Generation in the London Built Environment

This paper critically reviews the current requirement for a 10% offset of carbon emission that should be obtained from on-site renewable and other carbon-saving energy sources installed in new office buildings in London built environment. Carbon saving effects of several currently available renewable-based generation technologies for use in contemporary office developments are calculated and compared in the paper. In order to allow direct and transparent comparison, the paper proposes a new index, expressed as the ratio of the total carbon dioxide offset with the total cost of technology, calculated over the lifetime period of use. The presented results include sensitivity analysis of the following parameters and factors of influence: Capital costs of technologies, availability of primary energy sources, system efficiencies, and system losses. The paper also provides a discussion of the possible changes in the current carbon offset legislation and future carbon mitigation policy implications.     

Calibration system for electronic instrument transformers with digital output

A high-accuracy system for calibration of electronic instrument transformers with digital output is described. Its design is based on International Electrotechnical Commission (IEC) standards 61850, 60044-8, and 60044-7. The performance of the calibration system has been evaluated. Its estimated relative uncertainty (2/spl sigma/) is within 40/spl middot/10/sup -6/ in magnitude and within 40 /spl mu/rad in phase.     

A new improvement to the Powell and Chau linear phase IIR filters

An improvement to the realization of the linear-phase IIR filters is described. It is based on the rearrangement of the numerator polynomials of the IIR filter functions that are used in the real-time realizations proposed in literature. The new realization has better total harmonic distortion when a sine input is used, and it has smaller phase and group delay errors due to finite section length     

An optically isolated hybrid two-stage current transformer for measurements at high voltage

The development of a high-voltage (HV) current measurement system for on-site/in-situ calibrations in power systems is described in the paper. The system is based on an optically isolated hybrid two-stage current transformer with electronic circuitry that performs A/D conversion. It uses a fiber optic link for data transmission to a ground station and a laser-driven fiber optic link for supplying power to the electronic circuitry of the remote module at HV. The uncertainty of the current-ratio measurement is estimated to be less than 100/spl middot/10/sup -6/ both in-phase and quadrature.     

Recommendations for energy efficient and visually acceptable street lighting

While designing new street lighting installations or dealing with reconstructions of the existing ones, lighting designers usually do not take into consideration all of the available means for energy savings and optimal performance. This paper offers a set of the most important recommendations regarding the relevant influencing factors for energy savings in street lighting, the majority of which represent the results and conclusions of original research. Recommendations which result from user needs and regard visual quality are also briefly presented. Taking all of these recommendations into account provides improvement of appearance and sense of security, as well as energy and cost savings.