139 research outputs found
Do Consumers Trust the National Inspection Exemption Brands? Evidence from Infant Formula in China
Consumers are often uncertain about product quality and have to rely on different information, either given or pursued, to assess quality. Developing countries may lack institutional and technical resources to rigorously monitor and enforce product quality standards and/or to implement market-based instruments where market failures are common. The information-based instruments on product quality may work well in these countries as they reduce information asymmetry between firms and consumers. This study investigates one particular information-based instrument, the National Inspection Exemption (NIE) system in China. China launched the National Inspection Exemption (NIE) System in various industries in 2000 to award firms who are in compliance with the quality standards, to inform consumers of product quality, and to lessen the pressure on regulatory monitoring and enforcement of product quality standards. Once a firm is granted the NIE title by China's National Administration of Quality Supervision, Inspection and Quarantine (AQSIQ), its products are exempted from quality inspections by all governmental agencies at different levels for three years; but it is obligated to report the product quality condition to the local AQSIQ office annually. The NIE titled firms are also allowed to include the title in the product label and to use the status in the advertisement campaign. Based on the theoretical framework, we establish the hypothesis that consumers are more willing to buy the product with the NIE title and the NIE title is likely to increase sales revenue when consumers lack of means to assess quality. The empirical application of China dairy industry supports the theoretical hypothesis. In particular, using the firm-level panel data, we find that the NIE title boots sales revenue and the impact is both statistically and economically significant based on the difference-in-difference estimate and the random-fixed effect estimations. Furthermore, using the survey data collected right after the 2008 China milk scandal regarding the brand choice of infant formula among 1,228 mothers with infants and young children, we find that consumers’ preference for the NIE title still present even the NIE titled firms are involved in a food scare event. The positive NIE preference is particularly strong among highly educated consumers and those who buy domestic brands.brand choice, food safety, product quality, national inspection exemption, quality standards, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics,
Pollution taxation in China : the impact of inspections
This study assesses the effectiveness of the enforcement process used to implement China’s main industrial pollution clean-up legislation. Liguo Lin from the School of Economics at the Shanghai University of Finance and Economics is the study’s author. Using information from over 135 firms based in Fuzhou, the capital city of the Fujian province, he assesses how companies respond to environmental enforcement inspections and whether these inspections lead to improvements in the firms’ environmental performance. The study finds that many firms under-report their pollution production levels. This happens when they take part in the self-reporting process that is a key stage of China’s pollution control system. The study also shows that, while enforcement inspections do improve the veracity of the pollution reports that firms submit, these inspections do not significantly reduce the amount of pollution that firms produce. The study has important implications for policy makers as it shows that current environmental legislation and enforcement is not working. It shows that in order to control pollution both legislation and enforcement must be reformed to provide incentive for firms to actually reduce the amount of pollution they produce
Family Companionship and Elderly Suicide: Evidence from the Chinese Lunar New Year
Mental health problems among the elderly have attracted increasing attention. The most serious mental health problems may result in suicide, and lack of family companionship is often speculated to be a major cause. In this paper, we use high-frequency suicide rate data and utilize a novel temporal variation in the lunisolar calendar to provide evidence on the protective effects of the Chinese Lunar New Year (when the elderly people receive unusually high level of family companionship) on elderly suicide. We find that elderly suicide rate decreases by 8.7% during the Chinese Lunar New Year. In addition, the protective effects are stronger in counties where the typical level of daily family companionship for the elderly is lower. By contrast, we do not find similar protective effects for young and middle-age cohorts. We consider a variety of alternative mechanisms, and conclude that family companionship is an important channel for the protective effects of the Chinese Lunar New Year. Our study calls for greater attention to the mental health status and suicide problem of the elderly, especially with the rapid population aging and increasing prevalence of the “empty-nest” elderly in developing countries
A crystal plasticity study of cyclic constitutive behaviour, crack-tip deformation and crack-growth path for a polycrystalline nickel-based superalloy
Crystalplasticity has been applied to model the cyclicconstitutive behaviour of a polycrystalline nickel-based superalloy at elevated temperature using finite element analyses. A representative volume element, consisting of randomly oriented grains, was considered for the finite element analyses under periodic boundary constraints. Strain-controlled cyclic test data at 650 °C were used to determine the model parameters from a fitting process, where three loading rates were considered. Model simulations are in good agreement with the experimental results for stress–strain loops, cyclic hardening behaviour and stress relaxation behaviour. Stress and strain distributions within the representative volume element are of heterogeneous nature due to the orientation mismatch between neighbouring grains. Stress concentrations tend to occur within “hard” grains while strain concentrations tend to locate within “soft” grains, depending on the orientation of grains with respect to the loading direction. The model was further applied to study the near-tip deformation of a transgranular crack in a compact tension specimen using a submodelling technique. Grain microstructure is shown to have an influence on the von Mises stress distribution near the crack tip, and the gain texture heterogeneity disturbs the well-known butterfly shape obtained from the viscoplasticity analysis at continuum level. The stress–strain response near the crack tip, as well as the accumulated shear deformation along slip system, is influenced by the orientation of the grain at the crack tip, which might dictate the subsequent crack growth through grains. Individual slip systems near the crack tip tend to have different amounts of accumulated shear deformation, which was utilised as a criterion to predict the crack growth path
Crystal plasticity modelling of cyclic deformation for a polycrystalline nickel based superalloy at high temperature
Cyclic deformation at elevated temperature has been modeled for a polycrystalline nickel-based superalloy using the crystal-plasticity constitutive formulations. Finite element analyses were carried out for a representative volume element (RVE), consisting of randomly oriented grains and subjected to periodic boundary constraints. Model parameters were determined by fitting the strain-controlled cyclic test data at 650 °C for three different loading rates. Simulated results are in good agreement with the experimental data for both stress–strain loops and cyclic hardening behavior. The model was utilized to predict the stress relaxation behavior during the hold periods at the maximum and minimum strain levels, and the prediction compares well with the experimental results. Localized stress and strain concentrations were observed due to the heterogeneous nature of grain microstructure and the mismatch of the mechanical properties of individual grains
Oxygen diffusion and crack growth for a nickel-based superalloy under fatigue-oxidation conditions
Advanced microscopy characterisation and numerical modelling have been carried out to investigate
oxygen diffusion and crack growth in a nickel-based superalloy under fatigue-oxidation conditions.
Penetration of oxygen into the material and the associated internal oxidation, which leads to material
embrittlement and failure, have been found from Focused Ion Beam (FIB) examinations. Applied
fatigue loading tends to enhance the extent of internal oxidation for temperatures at 750°C and
above. Using a submodelling technique, finite element analyses of oxygen penetration at grain level
have been carried out to quantify the fatigue-oxidation damage and calibrate the diffusion parameters
based on the measurements of maximum depth of internal oxidation. The grain microstructure was
considered explicitly in the finite element model, where the grain boundary was taken as the primary
path for oxygen diffusion. A sequentially coupled mechanical-diffusion analysis was adopted to
account for the effects of deformation on diffusion during fatigue loading, for which the material
constitutive behaviour was described by a crystal plasticity model at grain level. Prediction of
oxidation-assisted crack growth has also been carried out at elevated temperature from the finite
2
element analyses of oxygen diffusion near a fatigue crack tip. A failure curve for crack growth has
been constructed based on the consideration of both oxygen concentration and accumulated inelastic
strain near the crack tip. The predictions from the fatigue-oxidation failure curve compared well with
the experimental results for triangular and dwell loading waveforms, with significant improvement
achieved over those predicted from the viscoplastic model alone
Modelling of cyclic plasticity and crack-tip deformation in a single crystal nickel-based superalloy
In this paper, cyclic plasticity in a single crystal nickel-based superalloy CMSX4 at elevated temperature was modelled using crystal plasticity (CP) and discrete dislocation dynamics (DDD). The CP modelling was carried out at the continuum level based on shear deformation along the octahedral slip systems. The DDD approach was implemented for a representative volume element with periodical boundary conditions. The DDD model parameters were calibrated using the predicted response by the CP model. The obtained numerical results by the two models compared with each other under strain-controlled monotonic and cyclic loading conditions in both and orientations. The CP model was further applied to study crack-tip deformation under fatigue loading. Stress-strain responses, as well as stress and strain distributions, near the crack tip were particularly monitored to assess the role of cyclic plasticity in controlling fatigue-crack propagation. The work has applications in life assessment of nickel-based superalloy components for high-temperature application
Learning the Relation between Similarity Loss and Clustering Loss in Self-Supervised Learning
Self-supervised learning enables networks to learn discriminative features
from massive data itself. Most state-of-the-art methods maximize the similarity
between two augmentations of one image based on contrastive learning. By
utilizing the consistency of two augmentations, the burden of manual
annotations can be freed. Contrastive learning exploits instance-level
information to learn robust features. However, the learned information is
probably confined to different views of the same instance. In this paper, we
attempt to leverage the similarity between two distinct images to boost
representation in self-supervised learning. In contrast to instance-level
information, the similarity between two distinct images may provide more useful
information. Besides, we analyze the relation between similarity loss and
feature-level cross-entropy loss. These two losses are essential for most deep
learning methods. However, the relation between these two losses is not clear.
Similarity loss helps obtain instance-level representation, while feature-level
cross-entropy loss helps mine the similarity between two distinct images. We
provide theoretical analyses and experiments to show that a suitable
combination of these two losses can get state-of-the-art results. Code is
available at https://github.com/guijiejie/ICCL.Comment: This paper is accepted by IEEE Transactions on Image Processin
Modelling plastic deformation in a single-crystal nickel-based superalloy using discrete dislocation dynamics
Background: Nickel-based superalloys are usually exposed to high static or cyclic loads in
non-ambient environment, so a reliable prediction of their mechanical properties, especially
plastic deformation, at elevated temperature is essential for improved damage-tolerance
assessment of components.
Methods: In this paper, plastic deformation in a single-crystal nickel-based superalloy CMSX4
at elevated temperature was modelled using discrete dislocation dynamics (DDD). The DDD
approach was implemented using a representative volume element with explicitly-introduced
precipitate and periodic boundary condition. The DDD model was calibrated using stress-strain
response predicted by a crystal plasticity model, validated against tensile and cyclic tests at 850°C
for and crystallographic orientations, at a strain rate of 1/s. Results: The DDD model was capable to capture the global stress-strain response of the
material under both monotonic and cyclic loading conditions. Considerably higher dislocation
density was obtained for the orientation, indicating more plastic deformation and much
lower flow stress in the material, when compared to that for orientation. Dislocation lines
looped around the precipitate, and most dislocations were deposited on the surface of precipitate,
forming a network of dislocation lines. Simple unloading resulted in a reduction of dislocation
density.
Conclusions: Plastic deformation in metallic materials is closely related to dynamics of
dislocations, and the DDD approach can provide a more fundamental understanding of crystal
plasticity and the evolution of heterogeneous dislocation networks, which is useful when
considering such issues as the onset of damage in the material during plastic deformation
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