The low-resolution analog-to-digital convertor (ADC) is a promising solution to significantly reduce the power consumption of radio frequency circuits in massive multiple-input multiple-output (MIMO) ...systems. In this letter, we investigate the uplink spectral efficiency (SE) of massive MIMO systems with low-resolution ADCs over Rician fading channels, where both perfect and imperfect channel state information are considered. By modeling the quantization noise of low-resolution ADCs as an additive quantization noise, we derive tractable and exact approximation expressions of the uplink SE of massive MIMO with the typical maximal-ratio combining (MRC) receivers. We also analyze the impact of the ADC resolution, the Rician K-factor, and the number of antennas on the uplink SE. Our derived results reveal that the use of low-cost and low-resolution ADCs can still achieve satisfying SE in massive MIMO systems.
•Both correct use and misuse of pesticides in rice production in China are common.•Farmers obtain information regarding pesticide use from various sources.•In contrast, pesticide retailers lead ...farmers to use pesticides less correctly.•More effects should be made to improve farmers’ pest control practices.
Substantial pesticide use results in severe negative externalities. The relationship of technology information with pest control practices and pesticide use among farmers is a crucial issue. However, it remains unclear how various information sources impact on farmers’ correct pesticide use. Using cross-sectional survey data covering 1135 rice-producing farmers in China, this study analyzes farmers’ pest control practices and information sources, and further investigates the impact of information sources on correct pesticide use. Results show that on average each farmer had 3.9 observations in which the applied pesticides well matched the target pests, accounting for 60.8% of a total of 7317 pest-control observations. At the household level, the average percentage of correct-use observations was even smaller than 62%. There were 35.6%, 30.1% and 25.4% of farmers obtaining information regarding pesticide use from personal experience, pesticide retailers and governmental agricultural extension agents, respectively. The Probit and Tobit estimation illustrate that farmers obtaining information regarding pesticide use from personal experience, governmental agricultural extension agents as well as Internet and media had a significantly higher probability and larger percentage of correct pesticide use in rice production, relative to those obtaining information from pesticide retailers. Several policy implications for improving farmers’ pest control practices are discussed.
In rural China, pesticide retailers are often accused of recommending farmers apply more pesticides than the scientifically recommended rate, while playing an important role in providing technical ...information regarding pesticide use to farmers. However, there is little empirical evidence on the relationship between pesticide retailers’ recommendations and farmers’ pesticide overuse. Using survey data from 1084 rice farmers in four provinces, this study utilized an endogenous switching probit model to examine the impact of pesticide retailers’ recommendations on the overuse of pesticides at the level of pest-control observation, accounting for potential self-selectivity bias. Results show that the proportion of pesticide overuse at the level of pest-control observation for controlling major pests, secondary pests, and weeds is 58.5, 55, and 40.6%, respectively. Pesticide retailers’ recommendations are found to increase the probability of pesticide overuse at the level of pest-control observation for controlling major pests, secondary pests, and weeds by 62.1, 59.3, and 58.3%, respectively. The robustness check using a conditional mixed process model provided consistent findings. Accordingly, this study proposes that more efforts should be made to provide additional technology training activities for pesticide retailers, strengthen regulations on pesticide retailers’ information recommendations, and further improve socialized agricultural technology services.
The Internet has become an important channel through which farmers obtain technical information regarding agricultural production. While previous studies have examined the effect of information from ...the Internet on technical efficiency in cash-crop production, there is little knowledge about how information from the Internet affects technical efficiency in grain production. This study aims to provide new evidence for the effect of information from the Internet on technical efficiency in rice production using the random survey data of 1122 rice farmers from the Yangtze River Basin in China. A stochastic frontier production function is employed to estimate technical efficiency in rice production, and the endogenous switching regression model is utilized to address the potential self-selectivity bias. The results show that 13.6% of surveyed rice farmers obtain information regarding agricultural production from the Internet. After addressing the self-selectivity bias, information from the Internet is found to increase rice farmers’ technical efficiency by 6.657 percentage points using the endogenous switching regression model. Meanwhile, information from the Internet exerts greater positive effects on technical efficiency in rice production among farmers with larger farm size and less farming experience as well as those in the Guizhou and Hubei provinces.
The vector neural network (VNN) based on memristor has tremendous potential in applications such as electronic reconnaissance, medical diagnosis, and speech processing. However, the VNNs that ...encompass a huge amount of multiply-accumulate (MAC) operations often acquire network weights through massive numerical calculations with high precision, which results in a heavy consumption of energy and computing resource. Nevertheless, the resistance states of existing memristive devices can hardly meet the high-precision regulation requirements that restricts the application of VNN. We propose a binary memristor based vector-type back propagation (BMVTBP) architecture that integrates the advantages of low-precision memristive devices and VNN. The core function of this architecture is to realize the low-precision weights of three states by employing binarized memristive synapses, and further construct the positive and negative synaptic arrays to implement the MAC operations of interval data. Simulations verify the identification performance of the BMVTBP architecture on the emitter library. The ensuing results demonstrate that the identification rates exceed 96% and 87% for the interval-value and scalar-value noisy emitter samples, respectively, with an architecture requirement of only 1920 memristive devices and an energy consumption of about 2.43e-10 J.
Both China’s national subsidy policies for plug-in electric vehicles (PEVs) purchasers and passenger cars corporate average fuel consumption and new vehicle credit regulation (dual-credit policy) ...favor long-range 300+ km battery electric vehicles (BEVs) and 80+ km plug-in hybrid electric vehicles (PHEVs). However, these electric vehicles tend to have lower energy efficiency and higher purchase and operation costs. Vehicle with larger batteries can also be less equitable because the subsidies are often provided to more expensive vehicles and wealthier owners. This study takes advantage of a novel dataset of daily driving data from 39,854 conventional gasoline vehicles in Beijing and 4999 PHEVs in Shanghai to determine the optimal range of BEVs and PHEVs within their respective cities. We simulate a model to explore ranges with which PEVs emit less GHGs than that of a baseline hybrid and conventional gasoline vehicle while ensuring that all daily travel demands are met. Our findings indicate that in both cities, the optimal ranges to balance cost and travel demand for BEVs are 350 km or less and for PHEVs are 60 km or less in Beijing and 80 km or less in Shanghai. We also find that to minimize carbon dioxide (CO
2
) emissions, the ranges are even lower 10 km in Beijing and 30 km in Shanghai. Our study suggests that instead of encouraging long-range PEVs, governments should subsidize PEV models with shorter ranges. Parallel efforts should also be made to both increase renewable energy over fossil fuels and expand charging facilities. Although individual mobility demand varies, the government could reduce occasional long-distance driving by subsidizing alternative transportation choices. Providing week-long driving trials to consumers before their purchases may help decrease the demand of very long range PEVs by alleviating the range anxiety through a learning process.
Purpose
The negative externalities of pesticide overuse increasingly concern the public. However, little empirical evidence has been provided for pesticide overuse and the relationship between the ...governmental agricultural extension system reforms and pesticide use in grain production from a nationwide perspective. The purpose of this paper is to estimate the productive effect and overuse of pesticides, and it also investigates the effect of the governmental agricultural extension system reforms on pesticide expenditure in rice, maize and wheat production in China.
Design/methodology/approach
A two-equation system model consisting of an exponential-specific damage-control production function and a pesticide use function is applied to the provincial-level data during the period 1985–2016.
Findings
While pesticide expenditure significantly increases grain productivity, the actual pesticide expenditure exceeds the economically optimal level. The commercialization reform of the governmental agricultural extension system contributed to the increase in pesticide expenditure. Moreover, the de-commercialization reform of the governmental agricultural extension system plays a limited role in pesticide reduction. Price fluctuations for grain and pesticide also impose significant effects on pesticide expenditure.
Originality/value
This study has two important policy implications for pesticide reduction in China. It is urgent to specify the functions of the governmental agricultural extension system, and encourage the development of the socialized agricultural technology service. More efforts should also be made to remove the bureaucratic intervention on the pricing mechanism of grain product and pesticide.
Choriocarcinoma is a cancer that usually occurs in the uterus during pregnancy. Although choriocarcinoma with renal metastasis and spontaneous renal hemorrhage is very rare, it can occur. We describe ...a rare case of metastatic choriocarcinoma, wherein the patient presented with acute abdominal pain due to a subcapsular hematoma secondary to a bleeding renal metastasis. We performed a laparoscopic nephron sparing surgery to remove the tumor and control the bleeding. A retrospective analysis revealed that metastasis was detected on
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F-fluorodeoxyglucose PET/CT, but not on CT alone. To our knowledge, a case of choriocarcinoma with such symptoms and treatment has not been described in recent literature. Our case illustrates that acute bleeding from a renal metastasis can be effectively managed by laparoscopic nephron sparing surgery. It also demonstrates the advantage
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F-FDG PET/CT may have in the evaluation of metastatic choriocarcinoma.
Increasing scene-awareness is a key challenge in video anomaly detection (VAD). In this work, we propose a hierarchical semantic contrast (HSC) method to learn a scene-aware VAD model from normal ...videos. We first incorporate foreground object and background scene features with high-level semantics by taking advantage of pre-trained video parsing models. Then, building upon the autoencoder-based reconstruction framework, we introduce both scene-level and object-level contrastive learning to enforce the encoded latent features to be compact within the same semantic classes while being separable across different classes. This hierarchical semantic contrast strategy helps to deal with the diversity of normal patterns and also increases their discrimination ability. Moreover, for the sake of tackling rare normal activities, we design a skeleton-based motion augmentation to increase samples and refine the model further. Extensive experiments on three public datasets and scene-dependent mixture datasets validate the effectiveness of our proposed method.
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