A figure of merit for overall performance and value of AFDD tools

A figure of merit, V, to characterize the value of an AFDD maintenance tool is presented. The AFDD tool is fed data representing air-conditioners operating with and without faults across a range of conditions. The calculation of V considers the probability of each scenario occurring, the tool's response, and the resulting implications. These results are summed to give a typical average value for deploying the AFDD tool, as compared to maintenance being performed without AFDD. Case studies illustrate the calculation of V. Six AFDD tools and two idealized tools are evaluated. Five of the six real tools give negative V, meaning that their use causes more harm than good. The sixth shows approximately $10 benefit per nominal ton of air-conditioner capacity per typical maintenance visit. This represents about half of the maximum potential value. These results demonstrate the importance of measuring AFDD performance and the potential monetary benefits of AFDD.     

Enhanced thermoelectric figure of merit of p-type half-Heuslers

Half-Heuslers would be important thermoelectric materials due to their high temperature stability and abundance if their dimensionless thermoelectric figure of merit (ZT) could be made high enough. The highest peak ZT of a p-type half-Heusler has been so far reported about 0.5 due to the high thermal conductivity. Through a nanocomposite approach using ball milling and hot pressing, we have achieved a peak ZT of 0.8 at 700 °C, which is about 60% higher than the best reported 0.5 and might be good enough for consideration for waste heat recovery in car exhaust systems. The improvement comes from a simultaneous increase in Seebeck coefficient and a significant decrease in thermal conductivity due to nanostructures. The samples were made by first forming alloyed ingots using arc melting and then creating nanopowders by ball milling the ingots and finally obtaining dense bulk by hot pressing. Further improvement in ZT is expected when average grain sizes are made smaller than 100 nm.     

Integrated figure of merit of public sector research evaluation

An approach for evaluation of research is described that integrates output indicators of four stages downstream the innovation process: immediate, intermediate, pre- ultimate and ultimate outputs. Indexes of leading output indicators are constructed. The indexes are integrated cumulatively to form an overall index of key output indicators, which is the integrated figure of merit (IFM). Data for the indicators are obtained from records and key informants, and the indicators are grouped by normalized weights. The paper also discusses the limitations and the methodological, conceptual and political/organizational issues of such an approach to research evaluation.     

High-performance bismuth-telluride compounds with highly stable thermoelectric figure of merit

The p-type (Bi_0.25Sb_0.75)₂Te₃ ingot doped with 8 wt% excess Te alone and the n-type Bi₂ (Te_0.94Se_0.06)₃ ingot codoped with 0.068 wt% I and 0.017 wt% Te were grown by the Bridgman method and annealed at 673 K for 5 h in a hydrogen stream. The electrical resistivity ρ, Seebeck coefficient α and thermal conductivity κ before and after annealing were measured at 298 K, so that the annealing degraded significantly ZT of the p-type specimen but enhanced remarkably that of the n-type one. The temperature dependences of ρ, α and κ of the as-grown p-type and annealed n-type specimens with higher ZT were investigated in the temperature range from 200 to 360 K. As a result, ZT values of the as-grown p-type and annealed n-type specimens have a broad peak and reached great values of 1.19 and 1.13 at approximately 320 K, respectively. The present materials were thus found to be far superior to any other bismuth-telluride compound in the thermal stability of energy conversion efficiency in addition to the high performance.     

锗纳米晶浮栅存储器的电荷存储特性

Ge纳米晶嵌入高k介质中既可以提高器件的可靠性又可以降低写入电压和提高存储速度.本实验主要研究了用于非挥发存储器的含有Ge纳米晶MIS结构的电荷存储特性.MIS结构由电子束蒸发的方法制备,包括Al2O3控制栅,Al2O3中Ge纳米晶和Al2O3隧道氧化层.这种MIS结构在1MHz下的C-V特性表现出良好的电学性能,平带电压漂移为0.96V,电荷存储密度达到4.17×1012cm-2.不同频率下Ge纳米晶在Al2O3介质中电荷存储特性随着频率的增加,平带电压的漂移和存储的电荷数减小.随着扫描速率的增加,平带电压的漂移和存储电荷也减小.     

Fabrication of nanostructure and formation of nanocrystal for non-volatile memory

In this work, we have demonstrated that the nanocrystal created by combining the self-assembled block copolymer thin film with regular semiconductor processing can be applicable to non-volatile memory device with increased charge storage capacity over planar structures. Self-assembled block copolymer thin film for nanostructures with critical dimensions below photolithographic resolution limits has been used during all experiments. Nanoporous thin film from PS-b-PMMA diblock copolymer thin film with selective removal of PMMA domains was used to fabricate nanostructure and nanocrystal. We have also reported about surface morphologies and electrical properties of the nano-needle structure formed by RIE technique. The details of nanoscale pattern of the very uniform arrays using RIE are presented. We fabricated different surface structure of nanoscale using block copolymer. We also deposited Si-rich SiNx layer using ICP-CVD on the silicon surface of nanostructure. The deposited films were studied after annealing. PL studies demonstrated nanocrystal in Si-rich SiNx film on nanostructure of silicon.     

Surface morphology and thermal figure of merit of a new compound thin film

The third nonlinear optical properties of a new compound 4,4′-bis(3-methoxy benzylidene amino) biphenyl doped poly-methyl methacrylate (PMMA) have been studied using Z-scan technique. Experiments are performed using a continuous waveguide (cw) diode laser at 532 nm wavelength and 0.68 kW/cm² laser intensity. The optical power limiting behavior of sample doped PMMA was also investigated. It also shows a very good optical limiting behavior with a limiting threshold of 4.7 mW. We attribute the nonlinear absorption and optical limiting property of the sample film to two photon absorption effect at 532 nm. The experimental evidences of observing diffraction pattern in compound 4,4′-bis(3-methoxybenzylideneamino) biphenyl doped PMMA has been present. The refractive index change, Δn, and nonlinear refractive index, n ₂ determined from the number of observed ring. We obtained good values of Δn = 105.154 × 10^?4and n ₂ = 154.154 × 10^?7 cm²/W. Variation of refractive index with temperature, dn/dT, and figure of merit, H, are found to be 8.858 × 10^?6 1/°C and 5.316 × 10^?6, respectively. This large nonlinearity is attributed to a thermal effect resulting from linear absorption. Theoretical diffraction pattern that agree well with experimental one are generated using a wave theory.     

A study of cycling induced degradation mechanisms in Si nanocrystal memory devices

The endurance of Si nanocrystal memory devices under Fowler-Nordheim program and erase (P/E) cycling is investigated. Both threshold voltage (V(th)) and subthreshold swing (SS) degradation are observed when using a high program or erase voltage. The change of SS is found to be proportional to the shift of V(th), indicating that the generation of interface traps plays a dominant role. The charge pumping and the mid-gap voltage methods have been used to analyze endurance degradation both qualitatively and quantitatively. It is concluded that high erase voltage causes severe threshold voltage degradation by generating more interface traps and trapped oxide charges.     

Influence of annealing on the distribution of thermoelectric figure of merit in bismuth-telluride ingots

The p-type (Bi_0.25Sb_0.75)₂Te₃ doped with 8 wt% excess Te alone and n-type Bi₂(Te_0.94Se_0.06)₃ codoped with 0.017 wt% Te and 0.068 wt% I were grown by the Bridgman method and were cut into a parallelepiped of 5 × 5 × 15 mm³, where the length of 15 mm is parallel to the freezing direction. The specimen is mounted on an X-Y stage and the temperature difference between two probes set at an interval of 1 mm was approximately 2.6 K. The local Seebeck coefficient α_ℓ and local electrical resistivity ρ_ℓ along the freezing direction were measured at a scan step of 1 mm before and after annealing at 673 K for 2 h in vacuum. The local thermal conductivity κ_ℓ was calculated from ρ_ℓ using the relation between κ and ρ obtained previously for a series of bismuth-telluride compounds. As a result, α_ℓ ρ_ℓ and κ_ℓ before and after annealing changed significantly from place to place, so that the effect of annealing on the local thermoelectric figure of merit (ZT)_ℓ was never uniform throughout the specimen surface. The maximum (ZT)_ℓ of the as-grown p- and n-type specimens reached surprisingly great values of 1.88 and 1.59 at 298 K, respectively, which correspond to about twice as large as those observed macroscopically by the conventional Seebeck coefficient apparatus with an interval (between two probes) of 8 mm. Probably, these maximum values of (ZT)_ℓ would be an upper limit of ZT for the p- and n-type bismuth- telluride bulk compounds, at least in the present fabrication method.     

Ultra-low lattice thermal conductivity and promising thermoelectric figure of merit in borophene via chlorination

Monolayer boron-based materials are of current interests due to its polymorphism.Herein,motivated by the recent experimental synthesis of semiconducting hydroge...     

Synthesis of cobalt-based nanocrystal layer in silicon dioxide for nonvolatile memory applications

Cobalt silicide (CoSi) nanocrystal (NC) layer distributed within narrow spatial region is synthesized by thermal annealing of a sandwich structure comprised of a thin cobalt (Co) film sandwiched between two silicon-rich oxide (SiO(x)) layers. It is shown that the size of the CoSi NCs can be controlled by varying the Co film thickness, an increase in the size with increasing thickness. Capacitance-voltage (C-V) measurements on a test metal/oxide/semiconductor (MOS) structure with floating gate based on CoSi NCs of 3.8 nm in diameter and 1.4 x 10(12) cm2 in density are shown to have C-V characteristics suitable for nonvolatile memory applications, including a C-V memory window of about 9.5 V for sweep voltages between -15 V and +8, a retention time >10(8) s, and an endurance > 10(6) program/erase cycles.     

A multiple-design-point approach for reliability-based design optimization

The application of design-point-based reliability-based design optimization (RBDO) methods is hindered by the challenge of multiple-design-point problems. In this article, to improve the commonality of design-point-based RBDO methods, a novel multiple-design-point (MDP) approach is developed. The MDP approach uses the trace of the design points from consequent reliability analysis iterations to identify whether there are multiple design points, then all of the design points are used to calculate shifting vectors for the sequential optimization and reliability assessment method, and the corresponding probabilistic constraints are moved to the feasible region along these multiple shifting vectors at the same time. With multiple shifted probabilistic constraints, the design feasibility associated with this probabilistic constraint will be satisfied. Two mathematical examples, a speed reducer design and a honeycomb crashworthiness design, are presented to validate the effectiveness of the MDP method. The results show that the MDP approach is effective for handling multiple-design-point problems.     

A framework for design optimization using surrogates

Design optimization is a computationally expensive process as it requires the assessment of numerous designs and each of such assessments may be based on expensive analyses (e.g. computational fluid dynamics method or finite element based method). One way to contain the computational time within affordable limits is to use computationally cheaper approximations (surrogates) in lieu of the actual analyses during the course of optimization. This article introduces a framework for design optimization using surrogates. The framework is built upon a stochastic, zero-order, population-based optimization algorithm, which is embedded with a modified elitism scheme, to ensure convergence in the actual function space. The accuracy of the surrogate model is maintained via periodic retraining and the number of data points required to create the surrogate model is identified by a k-means clustering algorithm. A comparison is provided between different surrogate models (Kriging, radial basis functions (Exact and Fixed) and Cokriging) using a number of mathematical test functions and engineering design optimization problems. The results clearly indicate that for a given fixed number of actual function evaluations, the surrogate assisted optimization model consistently performs better than a pure optimization model using actual function evaluations.     

A new optimization algorithm for solving complex constrained design optimization problems

This article presents the performance of a very recently proposed Jaya algorithm on a class of constrained design optimization problems. The distinct feature of this algorithm is that it does not have any algorithm-specific control parameters and hence the burden of tuning the control parameters is minimized. The performance of the proposed Jaya algorithm is tested on 21 benchmark problems related to constrained design optimization. In addition to the 21 benchmark problems, the performance of the algorithm is investigated on four constrained mechanical design problems, i.e. robot gripper, multiple disc clutch brake, hydrostatic thrust bearing and rolling element bearing. The computational results reveal that the Jaya algorithm is superior to or competitive with other optimization algorithms for the problems considered.     

Design optimization of a dual-core dispersion-compensating fiber with a high figure of merit and a large effective area for dense wavelength-division multiplexed transmission through standard G.655 fibers

We report design optimization in terms of index-profile parameters of a dual-core dispersion-slope-compensating fiber suitable for broadband dispersion compensation in standard G.655 and G.655b single-mode fibers over the C and L bands of fiber amplifiers and additionally over the S band for the G.655b fibers. It takes into account profiles that can be achieved with state-of-the-art fabrication techniques such as modified chemical-vapor deposition. Relatively high mode effective areas ensure the reduced sensitivity of the fiber to detrimental nonlinear effects when the fiber is integrated into a dense wavelength-division-multiplexed network. The theoretical figures of merit of these DCFs were found to be > or = 700 (ps/dB)/nm; furthermore, the estimated bend losses were also quite low, even for bend radii as small as 16 mm.     

Pyroelectric figure of merit for a calix [4] acid/amine alternate layer Langmuir–Blodgett film

In this work calix [4] acid (A) has been deposited alternately with calix [4] amine (B) using the LB film deposition technique to form a non-centrosymmetric ABABA… molecular architecture. Pyroelectric and dielectric electric measurements have been performed for a 31 layer calix [4] acid/amine alternate layer LB film. Pyroelectric coefficients for this LB film system have been obtained using a quasi-static measurement system. Dielectric measurements have been used to determine the dielectric constant and the dielectric loss tangent. The data obtained from pyroelectric and dielectric measurements have been used to calculate the figure of merit for these LB film systems which has a value of 2.56 μC m⁻² K⁻¹.