Models and Metrics to Enable Energy-Efficiency Optimizations

Power consumption and energy efficiency are important factors in the initial design and day-to-day management of computer systems. Researchers and system designers need benchmarks that characterize energy efficiency to evaluate systems and identify promising new technologies. To predict the effects of new designs and configurations, they also need accurate methods of modeling power consumption.     

ALTAR in action: knowledge management

This paper describes the knowledge management (KM) aspects of an action research (AR) project that took place in a large U.K. manufacturing organisation, Britvic Soft Drinks Ltd. The ALTAR (Achieving Learning Through Action Research) approach described in an earlier paper was developed through the KM project described in this paper. The ALTAR approach was intended to facilitate organisational learning and academic research and the study involved a number of AR cycles at different levels of the collaborating organisation. Theoretical concepts were taken from the academic literature and were developed for practical use and fed back into the academic research. The knowledge value chain, in particular, helped the organisation to focus on the essential aspects of KM. The research-led thinking was useful in helping Britvic staff to define and understand the importance of knowledge, to identify what knowledge assets they owned and to understand how that knowledge could be harnessed. The research facilitated individuals' understanding of how better to access the knowledge of others and to share their own knowledge to benefit the whole organisation. From an academic point of view, the AR project facilitated academic research, stimulated organisational change and learning provided useful material for research outputs, teaching and learning and promoted future research opportunities.     

High doped MBE Si p–n and n–n heterojunction diodes on 4H-SiC

The physical and electrical properties of heavily doped silicon (5×10¹⁹ cm⁻³) deposited by molecular beam epitaxy (MBE) on 4H-SiC are investigated in this paper. Silicon layers on silicon carbide have a broad number of potential applications including device fabrication or passivation when oxidised. In particular, Si/SiC contacts present several atractive material advantages for the semiconductor industry and especially for SiC processing procedures for avoiding stages such as high temperature contact annealing or SiC etching. Si films of 100 nm thickness have been grown using a MBE system after different cleaning procedures on n-type (0 0 0 1) Si face 8° off 4H-SiC substrates. Isotype (n–n) and an-isotype (p–n) devices were fabricated at both 500 and 900 °C using antimonium (Sb) or boron (B), respectively. X-ray diffraction analysis (XRD) and scanning electronic mircorscope (SEM) have been used to investigate the crystal composition and morphology of the deposited layers. The electrical mesurements were performed to determine the rectifiying contact characteristics and band offsets.     

A real-coding jumping gene genetic algorithm (RJGGA) for multiobjective optimization

This paper presents a real jumping gene genetic algorithm (RJGGA) as an enhancement of the jumping gene genetic algorithm (JGGA) [T.M. Chan, K.F. Man, K.S. Tang, S. Kwong, A jumping gene algorithm for multiobjective resource management in wideband CDMA systems, The Computer Journal 48 (6) (2005) 749-768; T.M. Chan, K.F. Man, K.S. Tang, S. Kwong, Multiobjective optimization of radio-to-fiber repeater placement using a jumping gene algorithm, in: Proceedings of the IEEE International Conference on Industrial Technology (ICIT 2005), Hong Kong, 2005, pp. 291-296; K.F. Man, T.M. Chan, K.S. Tang, S. Kwong, Jumping-genes in evolutionary computing, in: Proceedings of the IEEE IECON’2004, Busan, 2004, pp. 1268-1272]. JGGA is a relatively new multiobjective evolutionary algorithm (MOEA) that imitates a jumping gene phenomenon discovered by Nobel Laureate McClintock during her work on the corn plants. The main feature of JGGA is that it only has a simple operation in which a transposition of gene(s) is induced within the same or another chromosome in the genetic algorithm (GA) framework. In its initial formulation, the search space solutions are binary-coded and it inherits the customary problems of conventional binary-coded GA (BCGA). This issue motivated us to remodel the JGGA into RJGGA. The performance of RJGGA has been compared to other MOEAs using some carefully chosen benchmark test functions. It has been observed that RJGGA is able to generate non-dominated solutions with a wider spread along the Pareto-optimal front and better address the issues regarding convergence and diversity in multiobjective optimization.     

Characterization of Interfacial Properties in Fiber-Reinforced Cementitious Composites

For calculating interface properties from pullout tests, a simple theoretical model is proposed. The model enables calculating of the following material parameters: the parameter of shear stiffness of the fiber–matrix boundary layer, the shear bond strength, the frictional bond strength and the specific interfacial fracture energy. These parameters can be determined from the slope of the load-slip curve, the maximum pullout load and the corresponding slip value. Slip-controlled, multiple-fiber pullout tests were conducted in a closed-loop test system. The effects of embedment length of fibers on the model-predicted material parameters were examined. The model predictions were satisfactorily compared with some previously published test data.     

Fate and effect of the antioxidant ethoxyquin on a mixed methanogenic culture

The potential inhibitory effect of ethoxyquin, an antioxidant commonly used as a preservative in the food processing industry (e.g., for stabilizing dissolved air flotation residuals), was evaluated at concentrations up to 300 mg/L using a mixed, mesophilic (35 degrees C) methanogenic culture and dextrin, peptone and methanol as the carbon source. A batch assay conducted with a range of ethoxyquin concentrations did not result in any inhibition up to an ethoxyquin concentration of 75 mg/L, but severe inhibition of methanogenesis was observed at concentrations higher than 150 mg/L. Ethoxyquin addition to a batch reactor with the same mixed, methanogenic culture, at ethoxyquin concentrations gradually increasing over 100 days, resulted in a transient and a complete inhibition of methanogenesis at ethoxyquin concentrations of 150 and 300 mg/L, respectively. Acidogens were not significantly impacted, whereas aceticlastic and methanol degrading methylotrophic methanogens were impacted the most. Acclimation of the methanogenic culture to ethoxyquin was not observed over an incubation period of more than 100 days. Long-term (>100 days) incubation at sub-inhibitory ethoxyquin concentrations did not result in ethoxyquin biotransformation. Similarly, ethoxyquin biotransformation was not evident over an 8-day aeration period in a laboratory-scale activated sludge reactor operated under fully aerobic conditions. Ethoxyquin phase distribution tests conducted with the mixed, methanogenic culture at 1.61 g/L volatile solids concentration and nominal ethoxyquin concentrations equal to or higher than 300 mg/L resulted in solid phase/liquid phase ethoxyquin ratios equal to or higher than 1.0. The combined effect of ethoxyquin recalcitrance under anaerobic conditions along with its phase distribution, which favors biosolids, will result in ethoxyquin accumulation in anaerobic treatment systems used by the food processing industry. Such accumulation may pose concerns relative to inhibitory effects in these treatment systems and the disposal of ethoxyquin-bearing biosolids.     

A novel acrylic copolymer for a poly(alkenoate) glass-ionomer cement

The interest in the clinical use of polyalkenoate cements stems mainly from their behavior as bioactive adhesive materials with therapeutic action. Glass-ionomer cements set by an acid-base reaction between a degradable glass and a poly(alkenoic acid) and the therapeutic action is related to the release of fluoride ions which are present in the hardened cement that show a sustained release over years, responsible for caries inhibition in teeth. Conventional glass-ionomers, however, suffer from some disadvantages such as short working time, initial moisture sensitivity and prone to desiccation after setting and are generally brittle. In the present study, a poly(alkenoic acid) copolymer was synthesized based on acrylic acid and 2-hydroxyethylmethacrylate (HEMA) using azobisisobutyronitrile as the initiator and characterized. The acid–base reaction was carried out by reacting aqueous solutions of the new copolymer (40 and 60%) with a commercial aluminofluorosilicate glasses as used in conventional glass-ionomer cements. The results showed that the copolymer of HEMA and acrylic acid was a viable poly(alkenoic) acid for formation of glass-ionomer cements.     

A Novel Calibration Method for Phase-Locked Loops

A novel method to calibrate the frequency response of a Phase-Locked Loop is presented. The method requires just an additional digital counter to measure the natural frequency of the PLL; moreover it is capable of estimating the static phase offset. The measured value can be used to tune the PLL response to the desired value. The method is demonstrated mathematically on a typical PLL topology and it is extended to fractional-N PLLs. A set of simulations performed with two different simulators is used to verify the applicability of the method.This work was carried out as a part of an internship at the QCT department of Qualcomm CDMA Technologies.Marco Cassia was born in Bergamo, Italy, 1974. He received the M.Sc. degree in engineering from the Technical University of Denmark, Lyngby, Denmark, in May 2000 and the M.Sc. degree in electrical engineering from Politecnico di Milano, Italy, in July 2000.From July 2001 to July 2002 he was with the QCT department of Qualcomm CDMA Technologies, San Diego, working in the field of direct modulation synthesizers. He is currently working toward the Ph.D.degree at the Technical University of Denmark.His main research interests are in the areas of low-power low-voltage RF systems.Peter Shah was born in Copenhagen Denmark in 1966. He completed his MScEE and Ph.D at The Technical University of Denmark in 1990 and 1993 respectively. From 1993 to 1995 he was a post doctoral research assistant at Imperial College in London, England, working on switched-current circuits. In 1996 he joined PCSI in San Diego (subsequently acquired by Conexant) as an RFIC design engineer, working on transceiver chips for the PHS cellular phone system. In 1998 he joined Qualcomm, also in San Diego, where he worked on RFICs for CDMA mobile phones and for GPS. In December 2002 he joined RFMagic where he is currently working on RFICs for consumer electronics. His research interests lie mainly in RFIC architecture and design, including sigma-delta PLLs and A/D and D/A converters, LNAs, mixers, and continuous-time filters.Erik Bruun received the M.Sc. and Ph.D. degrees in electrical engineering in 1974 and 1980, respectively, from the Technical University of Denmark. In 1980 he received the B.Com. degree from Copenhagen Business School. In 2000 he also received the dr. techn. degree from the Technical University of Denmark.From January 1974 to September 1974 he was with Christian Rovsing A/S, working on the development of space electronics and test equipment for space electronics. From 1974 to 1980 he was with the Laboratory for Semiconductor Technology at the Technical University of Denmark, working in the fields of MNOS memory devices, I²L devices, bipolar analog circuits, and custom integrated circuits. From 1980 to 1984 he was with Christian Rovsing A/S. From 1984 to 1989 he was the managing director of Danmos Microsystems ApS. Since 1989 he has been a Professor of analog electronics at the Technical University of Denmark where he has served as head of the Sector of Information Technology, Electronics, and Mathematics from 1995 to 2001. Since 2001 he has been head of ØrstedDTU.His current research interests are in the areas of RF integrated circuit design and integrated circuits for mobile phones.     

Bayesian modeling of dynamic scenes for object detection

Accurate detection of moving objects is an important precursor to stable tracking or recognition. In this paper, we present an object detection scheme that has three innovations over existing approaches. First, the model of the intensities of image pixels as independent random variables is challenged and it is asserted that useful correlation exists in intensities of spatially proximal pixels. This correlation is exploited to sustain high levels of detection accuracy in the presence of dynamic backgrounds. By using a nonparametric density estimation method over a joint domain-range representation of image pixels, multimodal spatial uncertainties and complex dependencies between the domain (location) and range (color) are directly modeled. We propose a model of the background as a single probability density. Second, temporal persistence is proposed as a detection criterion. Unlike previous approaches to object detection which detect objects by building adaptive models of the background, the foregrounds modeled to augment the detection of objects (without explicit tracking) since objects detected in the preceding frame contain substantial evidence for detection in the current frame. Finally, the background and foreground models are used competitively in a MAP-MRF decision framework, stressing spatial context as a condition of detecting interesting objects and the posterior function is maximized efficiently by finding the minimum cut of a capacitated graph. Experimental validation of the proposed method is performed and presented on a diverse set of dynamic scenes.     

Quantifying shrinkage cracking in fiber reinforced concrete using the ring test

Tensile stress can develop in concrete when rest raint prevents the concrete from shrinking freely in response to drying, chemical reaction, or temperature reduction. When these tensile stresses exceed the tensile strength of the concrete, visible cracking may be expected to occur. While several test methods have been developed to assess a material's potential for early-age shrinkage cracking, this paper describes the use of the ‘ring-test’ for assessing the performance of a fiber reinforced concrete. An equation is presented that enables the residual stress that develops in the concrete ring specimen to be estimated. This expression is used to approximate the stress that is transferred across a crack. It is shown that for conventional fiber reinforced concrete (i.e., the mixtures described in this paper) the pre-peak mechanical properties (elastic modulus, splitting tensile strength and free shrinkage) are not influenced greatly by the addition of fibers. Rather, fibers appear to influence shrinkage-cracking behavior only after the crack begins to open. To better understand the role of fibers in mitigating early-age shrinkage cracking passive acoustic emission testing was used. Acoustic emission measurements indicate microcracking due to the heterogenous nature of the concrete and the presence of moisture gradients. The acoustic emission results highlight how a single crack begins to form into a visible crack. Finally, an approach is presented for estimating crack-width based on the strain data measured from the ring test. The role of the specimen geometry is discussed for comparing the ring test with field applications.