In many parts of the world, concerns about the COVID-19 pandemic and city quarantine policy have led to a general decline in the physical and mental health of residents due to insufficient social interaction. These adverse effects can cause potential public health risks. Ways to alleviate the adverse impact of the pandemic and meet social interaction needs must be widely addressed. This survey was conducted from 1–5 April 2020; it collected 386 responses from residents of Chengdu, China, during the pandemic based on an online survey questionnaire. The results indicate that most of the residents believe their health status is poor, and that they do not experience adequate social contact with others. Most of the respondents indicated no difference in mental health, while a few reported differences in their physical health and social interaction levels. Visiting urban parks can significantly improve overall health and assist in meeting individuals’ social interaction needs. Although residents have reduced the frequency of visits during the pandemic, even once a week can be beneficial. This paper emphasizes the critical role of urban parks during the pandemic period from the perspective of the urban building environment. The conclusion affirms that urban parks and large outdoor, open spaces can provide residents with a place for safe outdoor activities and social interaction in a green environment during a pandemic, as well as serve as a buffer area to maintain favorable health and quality of life.

While international trade in organic products has grown significantly, understanding consumers' preferences for imported organic foods has remained limited. This research examines the impact of country-of-origin labeling on US consumers' choices of organic foods. Results show that consumer valuation of domestically produced organic broccoli was significantly higher than that of imported organic broccoli. Adding information about USDA organic certification standards/rules for imported products mildly increases consumer valuation of imported organic broccoli in some cases. These findings suggest that providing such information may have a positive impact on consumer willingness to purchase imported organic products.JEL classifications: Q13

Using online surveys to elicit consumer preference is gaining popularity because of several advantages offered by this method. Past research mainly focuses on the comparison between online surveys and other survey modes. Few have explored methods of using online survey tools to improve data quality for consumer willingness-to-pay (WTP) estimates. This article determines the impact of using a validation question (VQ) approach that asked survey respondents to select a particular answer on improving online survey data quality across six countries. Results show that survey data quality is a common problem in online surveys across countries and the severity of this problem differs significantly. Using VQs might detect the respondents who are less careful in answering survey questions, thus providing less reliable answers. The econometric models for respondents who correctly answer VQs (pass VQs) perform significantly better than the models for respondents who incorrectly answer VQs (fail VQs). The WTP estimates for respondents who pass and fail VQs differ significantly; and in general the WTP estimates for respondents passing VQs have smaller variances than those for all respondents and for respondents failing VQs. Le recours aux enquêtes en ligne pour caractériser les préférences des consommateurs gagne en popularité en raison de ses nombreux avantages. Les recherches antérieures se sont principalement limitées a comparer les enquêtes en ligne et les autres types d'enquêtes. Peu se sont penchées sur l'utilisation d'outils susceptibles d'améliorer la qualité des données recueillies lors d'enquêtes en ligne destinéesà evaluer le consentementà payer des consommateurs. Dans le présent article, nous analysons l'impact liéà l'utilisation d'une méthode comprenant une question de validation dans laquelle on demandait aux répondants de choisir une réponse en particulier pour améliorer la qualité des données d'enquête en ligne dans six pays. Les résultats de notreétude montrent que la qualité des données d'enquête est un problème courant dans les paysà l'étude et que la gravité du problème varie considérablement d'un paysà l'autre. Le fait d'inclure des questions de validation permettrait de déceler les répondants qui sont moins consciencieux lorsqu'ils répondentà des questionsd'enquête et qui, par conséquent, fournissent des réponses plus ou moins fiables. Selon notreétude, les modèleséconométriques qui utilisent les données de répondants qui ont répondu correctement aux questions de validation donnent de meilleurs résultats que les modèles qui utilisent les données de répondants qui n'y ont pas répondu correctement; l'écart entre les estimations du consentementà payer des deux groupes de répondants varie considérablement. En règle générale, les estimations du consentementà payer des répondants qui ont répondu correctement aux questions de validation présentent de plus faibles variances que celles pour l'ensemble des répondants et pour ceux qui n'ont pas répondu correctement aux questions de validation.

Halide perovskite has been widely studied as a new generation of photoelectronic materials. However, their thermal and humidity-induced emission quenching have greatly limited their utility and reliability. Here, we report a hexagonal Mn 2 + -doped CsCdCl 3 perovskite crystal that possesses stable photoluminescence (PL) at both high temperature and humidity. The room temperature long-persistent luminescence (LPL) of the single crystals lasts up to 1480 s and can be adjusted by changing the concentration of Mn 2 + ion doping. The characteristic emission of d-d transition of Mn 2 + is realized, and the photoluminescence quantum yield (PLQY) is up to 91.4 %, it can maintain more than 90 % of the initial PL spectral integral area at 150 °C (423 K). High humid stability PL can be achieved more than 75 % of the initial PL intensity after 55 days of immersion in water. These excellent properties show the application prospect of the LPL material in lighting indication and anti-counterfeiting.

This paper addresses discrete optimization via simulation. We show that allowing for both a correlated prior distribution on the means (e.g., with discrete Kriging models) and sampling correlation (e.g., with common random numbers, or CRN) can significantly improve the ability to quickly identify the best alternative. These two correlations are brought together for the first time in a highly sequential knowledge-gradient sampling algorithm, which chooses points to sample using a Bayesian value of information (VOI) criterion. We provide almost sure convergence guarantees as the number of samples grows without bound when parameters are known and provide approximations that allow practical implementation including a novel use of the VOI's gradient rather than the response surface's gradient. We demonstrate that CRN leads to improved optimization performance for VOI-based algorithms in sequential sampling environments with a combinatorial number of alternatives and costly samples.