Application of Long-short Term Memory (LSTM) Model for Forecasting NOx Emission in Pohang Area

Emissions of nitric oxide and nitrogen dioxide, which are named as NOx, are a major environmental and health concern.To react to the climate crisis, the South Korean government has strengthened NOx emission regulations. An accurate NOx prediction model can help companies to meet their NOx emission quotas and achieve cost savings. This study focuses on developing a model which forecasts the amount of NOx emissions in Pohang, a heavy industrial city in South Korea with serious air pollution problems.In this study, the Long-short term memory (LSTM) modeling is applied to predict the amount of NOx emissions, with missing data imputation using stochastic regression. Two parameters (i.e., time windows and learning rates) necessary to run the LSTM model are tested and selected using the Adam optimizer, one of the popular optimization methods in LSTM. I found that the model that I applied achieved the acceptable prediction performance since its Mean Absolute Scaled Error (MASE), the most important evaluation criterion, is less than 1. This means that applying the model that I developed in predicting future NOx emissions will perform better than a naive prediction, a model that simply predicts them based on the last observed data point

The Efficiency Test of the North Korean Rice Market

This study aims to test whether North Korea’s rice market is efficient from Eugene Fama’s point of view. North Korea is the last communist country with a planned economy. While the government controls some extent of supply and demand and, thus, prices, most economic activities are through self-organized markets. The market efficiency, if any, would provide necessary implications not only to economic theories, but to policy designers of both parts of Korea for economic coordinations that might come shortly. To this end, this study sets three hypotheses for three major rice markets: i) the same price distributions, ii) simultaneous feedbacks among the markets, iii) law of one price holds for the markets. The results show that there is statistically no difference in the mean or variance among the three markets’ prices. The Granger causality test results reveal that the price in Pyeongyang, the capital city and that in Shinuiju, the most active in border-trade with China, affect each other simultaneously. Lastly, the law of one price holds between the Pyeongyang market and the North Korea-China border markets. These results are both surprising and interesting, even though there are still rooms for improvement. The results of this study can serve as a stepping-stone for future research on markets and economic institutions in North Korea

An Efficient TDOA-Based Localization Algorithm without Synchronization between Base Stations

An efficient localization algorithm is proposed by utilizing the time difference of arrival (TDOA) without synchronization between base stations. Generally, a TDOA-based localization algorithm requires synchronization between base stations in order to improve the accuracy of localization. Hence, correlations using wideband signals or wire connections between base stations have been used to synchronize the base stations; however, these approaches result in additional operating costs. Thus, the proposed algorithm does not require synchronization between base stations. The TDOA equations are derived by continuously varying the locations of the source and the location of a base station. The number of packets necessary for localization is also reduced. The localization performance of the proposed algorithm is verified with Monte-Carlo simulations

Chirp Spread Spectrum Transceiver Design and Implementation for Real Time Locating System

A chirp spread spectrum (CSS) transceiver architecture for IEEE 802.15.4a is proposed and implemented. In the transmitter, the size of the read-only memory that stores CSS signal samples for the chirp modulator is reduced by removing duplicate samples among subchirps. In the receiver, a matched filter is utilized to remove the other band noise caused by the band hopping property of CSS. A robust time synchronizer and chirp demodulator based on the matched filter are proposed. Low complexity architectures of the matched filter and biorthogonal decoder are also proposed. All of the proposed architectures are implemented in the field-programmable gate array chip and verified

Ring opening dynamics of a photochromic diarylethene derivative in solution

Photochromic ring opening reaction dynamics of 1,2-bis(2-methylbenzo[b]thiophen-3-yl)hexafluorocyclopentene in solution has been studied by femtosecond time-resolved fluorescence and transient absorption measurements. Time profiles of the transient absorption at several different probe wavelengths are identical, showing two time constants, 4 and 22 ps. The spontaneous fluorescence reveals time profiles identical to that in the transient absorption. A simple one step ring opening reaction mechanism is proposed, where the closed form in the excited state reaches the open form in the ground state through nonadiabatic curve crossing. The ring opening reaction rate is determined to be in the range (1.7-4) x 10(10) s(-1). A single 66 cm(-1) wave packet motion in the excited state is observed, whose role on the ring opening reaction is speculated upon

Surface-Enhanced Raman Scattering of Single- and Few-Layer Graphene by the Deposition of Gold Nanoparticles

Surface-enhanced Raman scattering (SERS) of graphene on a SiO(2)(300 nm)/Si substrate was investigated by depositing Au nanoparticles using thermal evaporation. This provided a maximum enhancement of 120 times for single-layer graphene at 633 nm excitation. SERS spectra and scan images of single-layer and few-layer graphene were acquired. Single-layer graphene provides much larger SERS enhancement compared to few-layer graphene, while in single-layer graphene the enhancement of the G band was larger than that of the 2D band. Furthermore, the D bands were identified in the SERS spectra; these bands were not observed in a normal Raman spectrum without Au deposition. Appearance of the D band is ascribed to the considerable SERS enhancement and not to an Au deposition-induced defect. Lastly, SERS enhancement of graphene on a transparent glass substrate was compared with that on the SiO(2)(300 nm)/Si substrate to exclude enhancement by multiple reflections between the Si substrate and deposited Au nanoparticles. The contribution of multiple reflections to total enhancement on the SiO(2)(300 nm)/Si substrate was 1.6 times out of average SERS enhancement factor, 71 times.close564

Robust self-cancellation-based time-of-arrival estimation algorithm to carrier frequency offset for bi-directional chirp signals

This study presents a robust self-cancellation-based time-of-arrival (TOA) estimation algorithm against carrier frequency offset (CFO). The proposed algorithm is developed to exploit the up and down chirp of bi-directional chirp signals. Using the relationship between the phase shifts of the transformed signals of the up and down chirp symbols, the CFO-induced error of the TOA estimates can be cancelled without pre-estimation and compensation through the proposed method. The root mean squared error of the proposed algorithm is analysed and verified through simulations in an additive white Gaussian noise and multi-path channel in the presence of CFO.FALS

Drought Tolerance Evaluation and Growth Response of Chinese Cabbage Seedlings to Water Deficit Treatment

Drought is a significant climatic factor that significantly affects the production of Chinese cabbage, a crop that is highly susceptible to drought stress. The development and cultivation of drought-tolerant varieties could be a viable strategy to minimize the damage caused by climate change and ensure stable production of Chinese cabbage. This requires the implementation of technologies for early evaluation and selection of a plethora of resources. In this study, we screened 100 varieties and breeding resources for drought tolerance under a water deficit treatment at the seedling stage. We also evaluated the growth response of Chinese cabbage varieties and breeding resources under water deficit treatment and selected drought-tolerant Chinese cabbage genotypes. We confirmed that the visual score for wilting, which evaluates the wilting response during the recovery process of Chinese cabbage seedlings through water deficit treatment and re-watering, can be used as an indicator for evaluating tolerance to drought stress. The visual score for wilting showed a high correlation with major traits representing drought tolerance. Our findings highlight the need for an integrated approach that considers various environmental conditions, varieties, and lines to select and develop drought-tolerant varieties. We selected ‘18-FH112-1’ and ‘18-FH112-1-2’ among others, and these germplasms will be useful resources for drought tolerance breeding. This study provides a foundation for future efforts to develop drought-tolerant Chinese cabbage varieties, thereby contributing to the stable production of this crucial crop