Masking effect produced by Mach bands on the detection of narrow bars of random polarity

Difficulties arise in measuring masking by Mach bands because very-low-contrast signals distort the bands. [J. Opt. Soc. Am. A 17, 1147 (2000).] Adding narrow luminance increments (bright bars) in the dark Mach band widens the dark band; adding decrements (dark bars) narrows the dark band, and conversely in the bright bands. Randomizing signal polarity prevents observers from using the distortion of the Mach bands as a cue to the presence of the signal. We measured (two-alternative-forced-choice) Mach bands' masking of randomly selected bright (incremental) or dark (decremental) bars. Detection was worse in both dark and bright Mach bands than on the neighboring plateaus. Separate analysis of trials containing only one polarity signal revealed 9-cycle/deg oscillations in performance as a function of location. Oscillations in the two polarities were approximately 180 degrees out of phase.     

Half-cycle slip activity of persistent slip bands at different stages of fatigue life of polycrystalline nickel

The slip activity of persistent slip bands (PSBs) in polycrystalline nickel was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The half-cycle slip activity as well as the local shear strain amplitudes was investigated after half-cycle deformation at different numbers of cycles in the domain of stress saturation. Moreover, the fraction of grains containing cumulated PSBs and the accumulated volume fraction of PSBs was estimated depending on the number of cycles during fatigue life. The volume fraction of active PSBs during half-cycle deformation is significantly lower than the cumulated PSB volume and decreases with increasing number of cycles. Additionally, an increasing localization of cyclic plastic strain within the PSBs was observed. However, with increasing number of cycles the average local shear strain amplitude remains almost unchanged. Thus, PSBs in polycrystals are subjected to a life history which is characterized by active and inactive periods of their half-cycle slip activity during cyclic deformation at different stages of the saturation state.     

On the incremental plastic work and related aspects of invariance – Part I

Summary Taking for granted that the free energy function is invariant under a change of a finite strain measure and/or the reference configuration, Hill's transformation rules for selected fundamental constitutive quantities (such as tangent elastic modulus, plastic increments of total strain and work conjugate stress, the work of work-conjugate stress, the work expended in the plastic part of incremental strain etc.) are derived in a manner different from that of Hill. On this background distinguished by Hill [6] subtle aspects of invariance in mechanics of elastic plastic solids are discussed. It is shown that the plastic part of the increment of elastic strain energy (when taken with reverse sign) defines the true invariant incremental plastic work which in general is not equal to the work expended in the plastic part of the strain increment. It plays the role of a potential for the plastic part of the increment of work-conjugate stress. This fundamental fact has not found proper account in the literature. The analytical interrelations between two apparently different theoretical frameworks, Hill-Rice (fixed reference configuration) and Eckart-Mandel (mobile unloaded configuration) are discussed showing their equivalence. Since the transformation rules are complex in the general 3D case, the first part of the paper illustrates instructively the discussed aspects in a 1D situation (simple tension or simple extension).     

Mathematical modelling of container transfers and storage locations at seaport terminals

This paper models the seaport system with the objective of determining the optimal storage strategy and container-handling schedule. It presents an iterative search algorithm that integrates a container-transfer model with a container-location model in a cyclic fashion to determine both optimal locations and corresponding handling schedule. A genetic algorithm (GA), a tabu search (TS) and a tabu search/genetic algorithm hybrid are used to solve the problem. The implementation of these models and algorithms are capable of handling the very large problems that arise in container terminal operations. Different resource levels are analysed and a comparison with current practise at an Australian port is done.     

Density and enthalpy of liquid alkali metals at pressures to 1500 bars

The similarity principle is used to find the density and enthalpy of the fused alkali metals lithium, sodium, and potassium at pressures to 1500 bars, and cesium to 1000 bars.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 5, pp. 855–862, May, 1976.     

Oxygen pressure and measurement temperature dependence of defects related bands in zinc oxide films

The ZnO films were fabricated by pulsed laser deposition at various oxygen pressure on single crystal silicon substrate. The structural and optical properties were investigated at various measurement temperature. The results showed that all the films have good c-axis preferred orientation. The different defects in films were fabricated which can be caused by various oxygen pressure. The films deposited at 1 Pa oxygen pressure have the most intense and narrow UV emission, and did not exhibit the deep band emission at the various measurement temperature. With the decrease of measurement temperature, the V_O-, O_i- and O_Zn-related band energy decreases, which is opposed to the V_Zn-related defects, meanwhile, the intensity of O_i-related emission peak has a sharp increase.     

Evaluation of wind energy resource and wind turbine characteristics at two locations in China

The ten-year monthly mean wind speed data at 10, 50,100, 150 and 300 m heights over a typical year were statistically analyzed in this study to determine the potential for wind power generation at two locations (Urumqi and Xining) in China, using the two-parameters Weibull distribution function. The shape factor k and scale factor c were estimated by the maximum likelihood method. Fourteen small to medium sized commercially available wind turbines were selected for the two regions, and their mean energy outputs and capacity factors were all analyzed. Results showed that the maximum monthly mean wind speeds at different heights in Urumqi and Xining occur in November and December, respectively; while the minimum values of the two locations occur in June and July, respectively. The wind power class and potential of Urumqi and Xining are “class 1” and “poor” and “class 2” and “Marginal”, respectively. Urumqi is not suitable for large-scale electric wind-power application; however, small-scale wind turbines or wind-hybrid power systems might be a reasonable option for this site for supplying power. Xining has a better wind resource than Urumqi, and medium-scale wind turbines might be a reasonable option in Xining for supplying more electric energy. The mean energy outputs for the selected wind turbines range from 491 kWh/yr to 87,333 kWh/yr in Urumqi, while the values range from 1,071 kWh/yr to 167,237 kWh/yr in Xining. The capacity factors for these wind turbines in Urumqi and Xining range from 4.3% to 19.5% and 10.4%–27.9%, respectively. The aim of this paper is to promote the development of wind power in China by contributing to scholarly understanding of its impact on the geographical regions studied.     

Demic and cultural diffusion propagated the Neolithic transition across different regions of Europe

The Neolithic transition is the shift from hunting–gathering into farming. About 9000 years ago, the Neolithic transition began to spread from the Near East into Europe, until it reached Northern Europe about 5500 years ago. There are two main models of this spread. The demic model assumes that it was mainly due to the reproduction and dispersal of farmers. The cultural model assumes that European hunter–gatherers become farmers by acquiring domestic plants and animals, as well as knowledge, from neighbouring farmers. Here we use the dates of about 900 archaeological sites to compute a speed map of the spread of the Neolithic transition in Europe. We compare the speed map to the speed ranges predicted by purely demic, demic–cultural and purely cultural models. The comparison indicates that the transition was cultural in Northern Europe, the Alpine region and west of the Black Sea. But demic diffusion was at work in other regions such as the Balkans and Central Europe. Our models can be applied to many other cultural traits. We also propose that genetic data could be gathered and used to measure the demic kernels of Early Neolithic populations. This would lead to an enormous advance in Neolithic spread modelling.     

Transfer coefficients of dissociated hydrogen at pressures up to 1000 bars and temperatures up to 10,000°K

The results of a calculation relating to the viscosity and thermal conductivity of hydrogen at pressures of 1–1000 bars and temperatures of 2000–10, 000°K are presented.     

Gradient microstructure and superior strength-ductility synergy of AZ61 magnesium alloy bars processed by radial forging with different deformation temperatures

Gradient microstructure modification is a cost-efficient strategy for high strength without compromising ductility,which is urgently needed in the fundamental science of engineering materials.In this study,heterogeneous structures of AZ61 alloy bars with anisotropic gradients(with different grain size distribu-tions from the surface to the center)were observed to exhibit strong strength-ductility synergies under different deformation temperatures.The results reveal that the grain refinement process under medium-low temperature deformation conditions(≤ 350 ℃)consists of four transition stages along the radial direction,i.e.,twin activations and deformation band formations,dislocation cells and pile-ups,ultra-fine sub-grains,and randomly orientated quasi-micron grains.Different deformation temperatures have a great influence on twin activations and deformation band formations,and the high temperature can easily provoke the initiation of non-basal slip.The deformation bands were determined as a primary nucleation site due to their highly unstable dislocation hindrance ability.Analysis in combination with the Radial forging(RF)deformation process,the differences of dynamic precipitates can be attributed to microstructural difference and solubility limit of Al at different temperatures.By summarizing the ten-sile test results,the sample forged at 350 ℃ exhibited the best strength-ductility synergy,exhibiting the highest elongation(EL)of 23.2％with a 251 MPa yield strength(YS)and 394 MPa ultimate tensile strength(UTS)in center region,and combined with the highest strength value of 256 MPa YS and 420 MPa UTS in the center region,while the EL was slightly degraded to 19.8％.     

Mixed logit analysis of bicyclist injury severity resulting from motor vehicle crashes at intersection and non-intersection locations

Standard multinomial logit (MNL) and mixed logit (MXL) models are developed to estimate the degree of influence that bicyclist, driver, motor vehicle, geometric, environmental, and crash type characteristics have on bicyclist injury severity, classified as property damage only, possible, nonincapacitating or severe (i.e., incapacitating or fatal) injury. This study is based on 10,029 bicycleinvolved crashes that occurred in the State of Ohio from 2002 to 2008. Results of likelihood ratio tests reveal that some of the factors affecting bicyclist injury severity at intersection and non-intersection locations are substantively different and using a common model to jointly estimate impacts on severity at both types of locations may result in biased or inconsistent estimates. Consequently, separate models are developed to independently assess the impacts of various factors on the degree of bicyclist injury severity resulting from crashes at intersection and non-intersection locations.Several covariates are found to have similar impacts on injury severity at both intersection and non-intersection locations. Conversely, six variables were found to significantly influence injury severity at intersection locations but not non-intersection locations while four variables influenced bicyclist injury severity only at non-intersection locations. In crashes occurring at intersection locations, the likelihood of severe bicyclist injury increases by 14.8 percent if the bicyclist is not wearing a helmet, 82.2 percent if the motorist is under the influence of alcohol, 141.3 percent if the crash-involved motor vehicle is a van, 40.6 percent if the motor vehicle strikes the side of the bicycle, and 182.6 percent if the crash occurs on a horizontal curve with a grade. Results from non-intersection locations show the likelihood of severe injuries increases by 374.5 percent if the bicyclist is under the influence of drugs, 150.1 percent if the motorist is under the influence of alcohol, 53.5 percent if the motor vehicle strikes the side of the bicycle and 99.9 percent if the crash-involved motor vehicle is a heavy-duty truck.     

Evaluation of corrosion level of naturally corroded bars using different cleaning methods,computed tomography,and 3D optical scanning

Reliable methods are necessary to assess the corrosion level to establish links between structural performance and reinforcement corrosion in concrete structures. Hence, in this study, a set of naturally corroded bars were subjected to metallic brushing, acid immersion, and sandblasting for rust removal. Additionally, 3D optical, CT scanning, and weight loss measurements were used to evaluate the levels of corrosion. The results indicate that sandblasting is an optimal cleaning method. Weight loss measurements are sufficient when detailed information about corrosion is not required, and 3D scanning is preferred if information on corrosion variation along the bar is needed.     

Effect of the use of different types and dosages of mineral additions on the bond strength of lap-spliced bars in self-compacting concrete

In this study, nine different types of concrete were adopted: normal concrete (NC) with low slump (68 mm) and eight types of self-compacting concrete (SCC) in which cement was partially replaced by four kinds of replacements (25%, 30%, 35% and 40%) of class F fly ash (FA) and by four kinds of replacements (5%, 10%, 15% and 20%) of silica fume (SF). The main objective of this research was to evaluate the effect of different types and dosages of mineral additions on the moment capacities and stiffnesses of the beam specimens and the bond strength of tension lap-spliced bars embedded in NC and self-compacting concretes (SCCs). To achieve these objectives, 27 full-scale beam specimens (2000 × 300 × 200 mm) were tested. In all beam specimens, 20 mm reinforcing bars were used with a 300 mm splice length as tension reinforcement. The variable used was the amount of FA and SF incorporated into SCC. Each beam was designed with bars spliced in a constant moment region at midspan. The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. Moreover, bond strength of SCC beams was compared to that of NC beams of the same dimensions, steel configuration and approximately the same water-to-cement ratio. In conclusion, the beam specimens produced from SCC containing 5% SF and 30% FA had the highest normalized bond strength with 1.07 whilst the replacements of Portland cement (PC) by an equal weight of FA or SF in SCC had generally the positive effect on the bond strength of reinforcing bar regardless of the dosage of mineral admixture compared to the specimen with NC indicating that SCC due to its superior filling capability more effectively covered the reinforcements and the grain-size distribution and particle packing improved ensuring greater cohesiveness. Moreover, the beam specimens produced from SCC with SF had the greatest stiffness compared to other all beams as result of the improvement of concrete pore structure due to the pozzolanic activity and the filler effect of high fineness silica fume.     

Detection of explosives and related compounds by low-temperature plasma ambient ionization mass spectrometry

Detection of explosives is important for public safety. A recently developed low-temperature plasma (LTP) probe for desorption and ionization of samples in the ambient environment ( Anal. Chem. 2008 , 80 , 9097 ) is applied in a comprehensive evaluation of analytical performance for rapid detection of 13 explosives and explosives-related compounds. The selected chemicals [pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), cyclo-1,3,5-trimethylenetrinitramine (RDX), tetryl, cyclo-1,3,5,7-tetramethylenetetranitrate (HMX), hexamethylene triperoxide diamine (HMTD), 2,4-dinitrotoluene, 1,3-dinitrobenzene, 1,3,5-trinitrobenzene, 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,6-dinitrotoluene, and 4-nitrotoluene) were tested at levels in the range 1 pg-10 ng. Most showed remarkable sensitivity in the negative-ion mode, yielding limits of detection in the low picogram range, particularly when analyzed from a glass substrate heated to 120 °C. Ions typically formed from these molecules (M) by LTP include [M + NO(2)](-), [M](-), and [M - NO(2)](-). The LTP-mass spectrometry methodology displayed a linear signal response over three orders of magnitude of analyte amount for the studied explosives. In addition, the effects of synthetic matrices and different types of surfaces were evaluated. The data obtained demonstrate that LTP-MS allows detection of ultratrace amounts of explosives and confirmation of their identity. Tandem mass spectrometry (MS/MS) was used to confirm the presence of selected explosives at low levels; for example, TNT was confirmed at absolute levels as low as 0.6 pg. Linearity and intra- and interday precision were also evaluated, yielding results that demonstrate the potential usefulness and ruggedness of LTP-MS for the detection of explosives of different classes. The use of ion/molecule reactions to form adducts with particular explosives such as RDX and HMX was shown to enhance the selectivity and specificity. This was accomplished by merging the discharge gas with an appropriate reagent headspace vapor (e.g., from a 0.2% trifluoracetic acid solution).     

Computer science research articles: the locations of different section types,and a proposal for standardization in the structure

This paper presents an analysis of the structure of computer science research articles published in the Lecture Notes of Computer Science series. While it is clear that most articles start with an Introduction and end with a Conclusion, the structure of text between these two sections is rather diverse. We studied the positions of different section types, and analysed dependencies between them. As a result, we present a number of common patterns used by writers, and make suggestions on how to improve the presentation of research in computer science.     

External validity of a generic safety climate scale for lone workers across different industries and companies

Purpose

The goal of this study was to examine the external validity of a 12-item generic safety climate scale for lone workers in order to evaluate the appropriateness of generalized use of the scale in the measurement of safety climate across various lone work settings. External validity evidence was established by investigating the measurement equivalence (ME) across different industries and companies.

Method

Confirmatory factor analysis (CFA)-based and item response theory (IRT)-based perspectives were adopted to examine the ME of the generic safety climate scale for lone workers across 11 companies from the trucking, electrical utility, and cable television industries.

Results

Fairly strong evidence of ME was observed for both organization- and group-level generic safety climate sub-scales. Although significant invariance was observed in the item intercepts across the different lone work settings, absolute model fit indices remained satisfactory in the most robust step of CFA-based ME testing. IRT-based ME testing identified only one differentially functioning item from the organization-level generic safety climate sub-scale, but its impact was minimal and strong ME was supported.

Implications

The generic safety climate scale for lone workers reported good external validity and supported the presence of a common feature of safety climate among lone workers. The scale can be used as an effective safety evaluation tool in various lone work situations.