Technological character,function type,and the longevity of standardized knowledge

This study seeks to determine the validity of the current de jure standards management system. The de jure standard is an important tool for innovation policy. However, its review interval has been fixed in the management system and maintained without the use of empirical analysis to guide its development. Therefore, this study (1) examines the factors that affect the longevity of the standards, and (2) outlines methods for improving how the de jure standards are managed. Results indicate that design and mark standards influence the longevity of standardized knowledge. This is notable, given that design for innovation is an emerging area of research that is commonly studied through the analysis of design patent data. Taken together, this study’s major findings are twofold. First, different technological categories have significantly different effects on longevity. Because the longevity of some technological sectors is naturally longer than others, there exists a need for a more flexible interval system. Second, the longevity of the mark and design standard is longer than the longevity of other types of standards. Both developing and developed countries utilize the de jure standard, so the policy implications of these findings are widely applicable.     

Exploring the representativeness of the M5 competition data

The main objective of the M5 competition, which focused on forecasting the hierarchical unit sales of Walmart, was to evaluate the accuracy and uncertainty of forecasting methods in the field to identify best practices and highlight their practical implications. However, can the findings of the M5 competition be generalized and exploited by retail firms to better support their decisions and operation? This depends on the extent to which M5 data is sufficiently similar to unit sales data of retailers operating in different regions selling different product types and considering different marketing strategies. To answer this question, we analyze the characteristics of the M5 time series and compare them with those of two grocery retailers, namely Corporación Favorita and a major Greek supermarket chain, using feature spaces. Our results suggest only minor discrepancies between the examined data sets, supporting the representativeness of the M5 data.     

Online adaptive lasso estimation in vector autoregressive models for high dimensional wind power forecasting

Wind power forecasts with lead times of up to a few hours are essential to the optimal and economical operation of power systems and markets. Vector autoregression (VAR) is a framework that has been shown to be well suited to predicting for several wind farms simultaneously by considering the spatio-temporal dependencies in their time series. Lasso penalisation yields sparse models and can avoid overfitting the large numbers of coefficients in higher dimensional settings. However, estimation in VAR models usually does not account for changes in the spatio-temporal wind power dynamics that are related to factors such as seasons or wind farm setup changes, for example. This paper tackles this problem by proposing a time-adaptive lasso estimator and an efficient coordinate descent algorithm for updating the VAR model parameters recursively online. The approach shows good abilities to track changes in the multivariate time series dynamics on simulated data. Furthermore, in two case studies it shows clearly better predictive performances than the non-adaptive lasso VAR and univariate autoregression.     

大尺寸机载智能多功能显示器的设计与实现

分析了座舱显示系统发展现状和面临的问题，设计并实现了一种一体化、大屏幕显示的智能化多功能显示器。该型显示器通过FC-AE-ASM（Fibre Channel-Avionics Environment-Anonymous Subscriber Message）网络和高速串行总线高效传输图形数据，解决了图形处理及传输的瓶颈问题；采用ARINC661（座舱显示系统与用户系统的接口）标准，规范了任务处理和显示处理的接口设计标准；支持红外触控以提高人机信息的交互效率；采用工程优化设计以提高显示器抗恶劣环境的能力。应用表明智能多功能显示器运行可靠，相对于传统飞行显示器，在显示处理、数据传输和人机功效等方面具有显著优势。     

Are China’s regional agricultural productivities converging: How and why?

This article tests the hypotheses of convergence to a single level of total factor productivity (TFP), and a steady state of TFP growth rate in China’s agricultural sector. Based on multilateral TFP estimates we found that China’s agricultural sector has rebounded in recent years from a slower TFP growth in the 2005–2007 period. While convergence test results confirm a “catch-up” effect that provinces with lower TFP levels tend to grow faster than others, estimated rates of β convergence are conditional on how we capture the heterogeneity effect across regions. The rates of β convergence range from 0.016 to 0.039 under different model specifications. Estimates show that higher growth rates of educational attainment, R&D, and intermediate goods density (per unit of labor) can enhance TFP growth. Unfortunately, there is no evidence of an overall σ convergence, indicating that TFP levels are not converging except in the South region. It implies that to catch up with leading provinces, it would require extra efforts for those lagging behind by increasing their region-specific research investment, promoting rural educational attainment, and enhancing embodied technical change.     

The labour income share and the relative price of investment in the US: an empirical investigation

Several studies argue that the recent decline in the secular trend of the labour income share is mostly driven by capital-embodied technological progress which is typically identified with trend reductions in the relative price of investment. In this paper, I use data from the United States to assess the nature of the relationship between trends in the labour share and the relative price of investment. Results from co-integration tests reveal that the share and the relative price of investment are most likely not co-integrated. However, co-variation tests indicate that both time series share a common stochastic component, and additional tests of structural breaks point at the presence of a common change in the mean or trend of both series. These results suggest that capital-embodied or investment-specific technological progress may have played an important role in the decline of the secular trend of the labour share.     

Heteroskedasticity-consistent covariance matrix estimators for spatial autoregressive models

In the presence of heteroskedasticity, conventional test statistics based on the ordinary least squares (OLS) estimator lead to incorrect inference results for the linear regression model. Given that heteroskedasticity is common in cross-sectional data, the test statistics based on various forms of heteroskedasticity-consistent covariance matrices (HCCMs) have been developed in the literature. In contrast to the standard linear regression model, heteroskedasticity is a more serious problem for spatial econometric models, generally causing inconsistent extremum estimators of model coefficients. This paper investigates the finite sample properties of the heteroskedasticity-robust generalized method of moments estimator (RGMME) for a spatial econometric model with an unknown form of heteroskedasticity. In particular, it develops various HCCM-type corrections to improve the finite sample properties of the RGMME and the conventional Wald test. The Monte Carlo results indicate that the HCCM-type corrections can produce more accurate results for inference on model parameters and the impact effects estimates in small samples.     

Hedging and pricing early-exercise options with complex fourier series expansion

We introduce a new numerical method called the complex Fourier series (CFS) method proposed by Chan (2017) to price options with an early-exercise feature—American, Bermudan and discretely monitored barrier options—under exponential Lévy asset dynamics. This new method allows us to quickly and accurately compute the values of early-exercise options and their Greeks. We also provide an error analysis to demonstrate that, in many cases, we can achieve an exponential convergence rate in the pricing method as long as we choose the correct truncated computational interval. Our numerical analysis indicates that the CFS method is computationally more comparable or favourable than the methods currently available. Finally, the superiority of the CFS method is illustrated with real financial data by considering Standard & Poor’s depositary receipts (SPDR) exchange-traded fund (ETF) on the S&P 500® index options, which are American options traded from November 2017 to February 2018 and from 30 January 2019 to 21 June 2019.     

Flexibility in the gig economy: managing time on three online piecework platforms

Gig economy platforms seem to provide extreme temporal flexibility to workers, giving them full control over how to spend each hour and minute of the day. What constraints do workers face when attempting to exercise this flexibility? We use 30 worker interviews and other data to compare three online piecework platforms with different histories and worker demographics: Mechanical Turk, MobileWorks, and CloudFactory. We find that structural constraints (availability of work and degree of worker dependence on the work) as well as cultural‐cognitive constraints (procrastination and presenteeism) limit worker control over scheduling in practice. The severity of these constraints varies significantly between platforms, the formally freest platform presenting the greatest structural and cultural‐cognitive constraints. We also find that workers have developed informal practices, tools, and communities to address these constraints. We conclude that focusing on outcomes rather than on worker control is a more fruitful way to assess flexible working arrangements.     

博物馆类建筑工程费用估算研究

如何将建设资金控制在批复限额内,防止“三超”现象的出现,是博物馆类建筑投资估算编制的难点。分析博物馆类建筑的设计特点,梳理博物馆类建筑工程费用估算编制中的应注意的问题,总结出其不同于一般公共建筑工程费用构成的特点,旨在为博物馆类建筑工程费用估算的编制提供借鉴。