α-Fe_2O_3(SO_4~(2-),Sn)气敏电阻的温度响应特性

在气敏温度区域内研究了α-Fe_2O_3(SO_4~(2-),Sn)材料的电阻-温度特性,认为表面结构的变化导致温度特性出现峰值并呈现气敏性。可利用空气中电阻温度特性提供的信息改性或发现新的气敏材料。     

On the design of multiple key hashing files for concurrent orthogonal range retrieval between two disks

This paper concerns the following problem: given a set of multi-attribute records, a fixed number of buckets and a two-disk system, arrange the records into the buckets and then store the buckets between the disks in such a way that, over all possible orthogonal range queries (ORQs), the disk access concurrency is maximized. We shall adopt the multiple key hashing (MKH) method for arranging records into buckets and use the disk modulo (DM) allocation method for storing buckets onto disks. Since the DM allocation method has been shown to be superior to any other allocation methods for allocating an MKH file onto a two-disk system for answering ORQs, the real issue is knowing how to determine an optimal way for organizing the records into buckets based upon the MKH concept.

A performance formula that can be used to evaluate the average response time, over all possible ORQs, of an MKH file in a two-disk system using the DM allocation method is first presented. Based upon this formula, it is shown that our design problem is related to a notoriously difficult problem, namely the Prime Number Problem. Then a performance lower bound and an efficient algorithm for designing optimal MKH files in certain cases are presented. It is pointed out that in some cases the optimal MKH file for ORQs in a two-disk system using the DM allocation method is identical to the optimal MKH file for ORQs in a single-disk system and the optimal average response time in a two-disk system is slightly greater than one half of that in a single-disk system.     

Use of Response Surface Methodology to Investigate the Effectiveness of Commercial Enzymes on Buckwheat Malt for Brewing Purposes

The influence of two factors, total concentration and fraction of three pairs of commercial enzymes, which showed statistical significance (Biocellulase W with Hitempase 2XL, Biocellulase W with Amylo 300 and Amylo 300 with Hitempase 2XL), were studied for their overall effect on buckwheat wort quality using response surface methodology (RSM). This study revealed that the addition of increasing levels of Hitempase 2XL to the buckwheat mash increased colour, extract levels, wort filtration, fermentability and total fermentable extract (TFE), along with decreasing viscosity values. Results also determined a high level of fermentability when an enzyme combination of 30% Biocellulase and 70% Hitempase was added to the mash. The addition of increasing levels of Amylo 300 to buckwheat mashes resulted in increases in fermentability and total fermentable extract (TFE), along with increases in total soluble nitrogen (TSN), free amino nitrogen (FAN) and Kolbach index (KI). With regard to the proposed optimal regime, although no synergistic effect was found when the three enzymes were used together, the optimum conditions for the production of buckwheat wort with lowest viscosity, highest extract and optimal fermentability were achieved using a joint model. Overall, the findings of this study demonstrate the feasibility of producing wort suitable for the brewing of gluten‐free beer from 100% malted buckwheat with careful optimisation of enzyme types and dosage levels.     

Effect of Calcium Lactate, 4-Hexyl Resorcinol and Vacuum Packing on Physico-chemical, Sensory and Microbiological Qualities of Minimally Processed Litchi (Litchi chinensis Sonn.)

Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0–2% (w/v) calcium lactate (CL), 0–0.02% (w/v) 4‐hexyl resorcinol (4‐HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over‐wrapped with polypropylene film, vacuum‐packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2 °C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four‐factor, three‐level experimental design (D₆ Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4‐HR, in‐package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 0.01), whereas drip losses and microbial count increased significantly (P 0.01) with time. Drip loss was significantly (P 0.1) reduced by addition of CL. 4‐HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis.     

Emulsifying Capacity and Emulsion Stability of Soy Proteins Compared with Corn Germ Protein Flour

Both emulsifying capacity (EC) and emulsion stability (ES) increased with increasing concentrations from 0.4% to 0.8% of soy flour (SF), soy concentrate (SC), soy isolate (SI) and corn germ protein flour (CGPF) when studied by response surface methodology. EC and ES increased as pH increased from 6 to 8 in all samples. Increasing incubation temperatures of protein solutions from 20–70°C or from 4–20°C did not affect EC or ES, respectively. SF had the highest EC, followd by SI, SC, and CGPF.     

A Working Memory Workout: How to Expand the Focus of Serial Attention From One to Four Items in 10 Hours or Less.

Five individuals participated in an extensive practice study (10 1-hr sessions, 11,000 trials total) on a self-paced identity-judgment n-back task (n ranging from 1 to 5). Within Session 1, response time increased abruptly by about 300 ms in passing from n = 1 to n > 1, suggesting that the focus of attention can accommodate only a single item (H. Caravan, 1998; B. McElree, 2001). Within Session 10, response time was dramatically reduced and increased linearly with n for n ≤ 4, with a slope of about 30 ms. The data suggest that working memory consists of a focus of attention governed by a limited-capacity search, expandable through practice, and a content-addressable region outside the focus of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Susceptibility of Listeria monocytogenes strains to disinfectants and chlorinated alkaline cleaners at cold temperatures

Minimal inhibitory concentration (MIC), suspension and biofilm tests were used in evaluating the disinfecting efficacy of eight commercially available disinfectants and four chlorinated alkaline cleaners against 10 strains of Listeria monocytogenes at refrigerated temperatures. The adaptive response and cross-adaptation of L. monocytogenes to the disinfectants and chlorinated alkaline cleaners were investigated. The bactericidal components in the agents used were chlorine, quaternary ammonium compound (QAC), peracetic acid, ethanol and isopropanol. With some exceptions the disinfectants were efficient against the L. monocytogenes strains. One alkaline hypochlorite containing disinfectant was not efficient in the suspension and MIC tests at the lowest concentration recommended by the manufacturer. The chlorinated alkaline cleaners were effective against L. monocytogenes. A QAC-based disinfectant was found to be the least-effective agent on both glass bead-blasted polyethylene and stainless-steel surfaces. Adaptive and cross-adaptive responses of L. monocytogenes strains were observed towards the QAC-based agent, but over 2-fold increases to other agents were not observed. These results suggest that the adaptive responses of L. monocytogenes to disinfectants or chlorinated alkaline cleaners are of a minor concern.     

Characterization of temporal response, spectral responsivity and its spatial uniformity in photoconductive diamond detectors

Three photoconductive diamond detectors with highly oriented diamond (HOD) films fabricated by the same process were characterized with respect to temporal response, spectral responsivity and its spatial uniformity over the wavelength range from 190 to 250 nm. Temporal measurements showed a drift in the baseline, suggesting the presence of deep level carrier traps. The responsivity of specimen No. 2 was more than twice those of the other two specimens, but it showed an unpredictable current fluctuation. It was found that the spatial uniformities of all the specimens were too low for radiometric purposes. A prominent peak, thought to be due to photoemission, was found in the responsivity spatial distribution of specimen No. 3 under a negative applied voltage.     

BKX-Ⅰ型并联机床的谐响应分析

应用有限元分析软件(ANSYS),对BKXⅠ型并联机床进行谐响应分析,分别得到了机床各节点沿机床的虚拟轴X、Y和Z向的位移谐响应曲线。在此基础上,还分析了该机床的谐响应规律,并明确了谐响应的特点,为改善此类机床的动态特性提供了一定的参考依据。     

A new efficient numerical method and the dynamic analysis of composite laminates with piezoelectric layers

Firstly, a numerical method for the inversion of Laplace transform is developed and its accuracy is shown through examples. Then, a state-vector equation for the dynamic problems of piezoelectric plates is deduced directly from a modified mixed variational principle for piezoelectric bodies and its exact solution for the dynamic problems of simply supported rectangle piezoelectric plate is simply given. For multilayered hybrid plates, we derive the solution in terms of the propagator matrices. The techniques accounts for the compatibility of generalized displacements and generalized stresses on the interface both the elastic layers and piezoelectric layers, and the transverse shear deformation and the rotary inertia of laminate are also considered in the global algebraic equation of structure. Meanwhile, there is no restriction on the thickness and the number of layers. As an application of the numerical inversion of Laplace transform presented in this paper, typical numerical examples of the harmonic vibration and transient response are proposed and discussed. Since the highly accurate numerical results, they can serve as benchmarks to test various thick plate theories and various numerical methods, such as the finite and boundary element methods for transient response problems.