Low Average Efficiency Research Articles

Three-Dimensional Simulation of Charge-Trap Memory Programming—Part I: Average Behavior

This paper presents a detailed investigation of charge-trap memory programming by means of 3-D TCAD simulations accounting both for the discrete and localized nature of traps and for the statistical process ruling granular electron injection from the substrate into the storage layer. In addition, for a correct evaluation of the threshold-voltage dynamics, cell electrostatics and drain current are calculated in presence of atomistic doping, largely contributing to percolative substrate conduction. Results show that the low average programming efficiency commonly encountered in nanoscaled charge-trap memory devices mainly results from the low impact of locally stored electrons on cell threshold voltage in presence of fringing fields at the cell edges. Programming variability arising from the discreteness of charge and matter will be addressed in Part II of this paper.

Average power reduction for MSM optical signals via sparsity and uncertainty principle

Multiple subcarrier modulation is an appealing scheme for high-data rate optical communication. However a major drawback is its low average power efficiency. While subcarrier reservation is a common approach to combat this problem, little is known about the performance of algorithms that utilize subcarrier reservation. By combining properties of sparse signals with an abstract form of the Uncertainty Principle related to multiple subcarrier signals, we design an effective iterative method for constructing average-power-efficient multicarrier signals. Unlike most existing subcarrier reservation methods, our method provides a guaranteed bound for the achievable average power reduction as well as guaranteed rates of convergence. Numerical simulations demonstrate the performance of the proposed method.

Flexibility and small firms’ survival: further evidence from Malaysian manufacturing

This study investigates the role played by production flexibility in explaining the lasting presence of small firms alongside their larger counterparts in the market. The production flexibility hypothesis postulates that the market place provides room for both large and small firms because large firms benefit from low minimum average costs and static production efficiency, while small firms, with higher minimum average costs, are more flexible. Unlike previous studies that used data from developed economies, this study tests the hypothesis using industry data from a developing country, Malaysia. Results show that there exist a negative relationship between firm size and sales variability suggesting that large and small firms each have their own efficiency niches.

An empirical investigation on parallelization strategies for Scatter Search

As other metaheuristics, Scatter Search can gain from a parallel implementation. However, it is not clear beforehand which of the possible alternative parallelization strategies is more effective. To address this question, it has been selected as a test bed for empirical testing a classical combinatorial optimization problem, namely 0–1 knapsack problem, for which the sequential application of Scatter Search is well known. Two phases or groups of steps in the Scatter Search template have been identified as natural candidates for parallelization and several ways of carrying out that parallelization are proposed. An extensive experimental analysis involving 18 different parallel algorithms has been carried out testing the combinations of these alternative parallelization strategies on a battery of large random instances generated using a public code from the literature. The interpretation of the ANOVA results gives cues about the significance of the alternatives used in each phase and about the effect of the dynamic (vs. static) updating of the RefSet. A low average efficiency has been observed, although it has to be taken into account that, due to the termination condition used, not all algorithms tested carry out the same number of iterations.

Copper electrowinning from gold plant waste streams

Gold mining industries produce a considerable amount of waste streams containing cyanide and small quantities of copper, gold and other heavy metals. This effluent is usually treated by the AVR process, in order to recycle the cyanide to the leaching operation, however, this process is not efficient for the treatment of stable cyanide complexes. In this paper, the feasibility of copper electrowinning, and eventually residual gold, in a flow-by cell with nickel foam or a reticulated vitreous carbon (RVC) cathode and a cationic membrane was investigated. This process has shown to be environmental-friendly and despite the low average current efficiency and high energy consumption, it permitted the recovery of about 99.6% of the copper and the recycling of 99.4% of cyanide present in the effluent.

Linearity of X-band class-F power amplifiers in high-efficiency transmitters

Modern communication signals have time-varying envelopes with significant peak-to-average ratios, resulting in low average efficiency when amplified by commonly used linear power amplifiers (PAs). For linear amplification with increased average efficiency, the Kahn envelope-elimination-and-restoration method uses a highly efficient saturated PA. In this paper, an 8.4 GHz class-F PA with 55% maximum instantaneous efficiency at 610 mW output power, is experimentally characterized in several different biasing modes. Operated in linear mode with constant drain bias, this PA has 10% average efficiency. The suppression of two-tone intermodulation products is 27 dBc when operated at about 0.7 times the peak output power. For the same PA operated in a modified Kahn mode with drive and bias control, a comparable linearity (27.7 dBc) can be obtained at peak output power. Furthermore, the average efficiency increased to 44%, a factor of 4.4 over the linear fixed bias mode.

The Impact of Prospective Reimbursement on Nursing Home Efficiency

Data Envelopment Analysis (DEA) was used to estimate the relative efficiencies of nursing homes in Maine for 2 years before the introduction of a prospective payment system and for 2 years afterward. A multiple regression was performed in which the DEA-estimated efficiency was the dependent variable and a number of facility characteristics and study year were the independent variables. Study findings indicate that nursing home efficiency scores fell after the introduction of prospective reimbursement; that is, generally speaking, more inputs were being used per unit of output in the period after the introduction of prospective reimbursement than in the period preceding it. This may be the result of poor management, degraded quality of inputs, improved quality of outputs, or some other unobserved trend during this same period. The study also concludes that higher occupancy rates are associated with lower efficiencies and that patients in restraints produce severe negative effects on efficiency. In addition, it appears that a sudden increase in administrative hours in the final study year played a role in that year's lower average efficiency scores, but also that all input levels generally rose while output levels remained virtually constant.

Simultaneous concentration of four enteroviruses from tap, waste, and natural waters.

The efficiency of virus recovery from water was investigated by using a method which enabled the concentration of a mixture of four enteroviruses with determination of their individual recovery efficiencies. The four viruses used (poliovirus 1, coxsackievirus A9, coxsackievirus B1, and echovirus 7) represented each of the four major subgroups of enteroviruses. This method, which was based on selective antibody neutralization, was used to investigate the effects of input water quality on enterovirus concentration by Balston filters (grade C; Balston, Inc., Lexington, Mass.) and organic flocculation. With tap water, the average recovery efficiency of the four viruses was 97%. Concentration from natural waters, including samples from two lakes (Lake Kinneret and the Hula Nature Reserve) and the Mediterranean Sea, resulted in similarly high average recovery efficiencies. Echovirus 7 was recovered with a slightly lower average efficiency from these types of water than were the other viruses. In comparison with other types of water, virus concentration from Jerusalem wastewater generally had a slightly lower efficiency of recovery, ranging from 63 to 75% for each of the viruses, with an overall average of 68%. The ability of each concentration step, membrane filtration or organic flocculation, to recover the viruses from water was assayed. For the filtration step, although there were not large differences in virus recoveries from tap water, echovirus 7 was recovered with the lowest efficiency (72%), and poliovirus 1 was recovered with the highest (87%) efficiency. Overall virus recovery by the filtration step was least efficient for wastewater (73%) and most efficient for seawater (107%).(ABSTRACT TRUNCATED AT 250 WORDS)