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In coastal stow net fishing, the heavy weight of a typical anchor (750–1000 kg) can increase the risk of capsizing the boat and crew member injury during hoisting operations. Thus, to prevent these accidents, a reduction in the anchor weight is required. One strategy to achieve this is to reduce the resistance force of the fishing gear used, which would allow lighter anchors to be employed. This requires the accurate estimation of the resistance force for various gear designs. Therefore, the resistance force and shape during the operation of two representative types of coastal stow nets currently employed in the Korean coastal stow net fishing industry were investigated using simulations and modeling experiments. The modeled fishing gear was divided into four sections according to the mesh size. Based on the results, the twine thickness was reduced in order to target areas of the gear where the greatest resistance was observed, while the front part of the gear was redesigned to prevent the front of the net from being pushed back into a suboptimal shape. The proposed low-resistance fishing gear has the potential to improve occupational safety in the coastal stow net fishing industry. [ABSTRACT FROM AUTHOR]

This study proposes how to incorporate concurrent purchase data into e-commerce recommendation systems to improve their predictive accuracy. We identified that concurrent purchases account for about 23 % of total orders on Katcher's, a Korean e-commerce platform. Despite the prevalence of concurrent purchases, existing algorithms often overlook this aspect. We introduce a novel transformer-based recommendation algorithm to process a user's order history, including concurrent purchases. Each order is represented as a natural language sentence, capturing the order timestamp, product names and their attribute values, their corresponding categories, and whether multiple products were purchased together in a single order (i.e., a concurrent purchase). These sentences form a sequence, which serves as a training dataset for fine-tuning Bidirectional Encoder Representations from Transformers (BERT) with the Next Sentence Prediction objective. We validate our ideas by conducting experiments on Katcher's platform, demonstrating the proposed method's improved prediction performance compared to existing recommendation systems, with enhanced accuracy and F1 score. Notably, the normalized discounted cumulative gain (NDCG) showed a significant improvement with a large margin. Furthermore, we demonstrate the beneficial impact of integrating concurrent purchase information on prediction performance. [ABSTRACT FROM AUTHOR]

South Korea has developed road-based transportation and uses a lot of gasoline. South Korea imports gasoline since it is not produced domestically. So, fluctuations in gasoline prices have a significant impact on the national economy. Currently, gasoline orders, which are based on gasoline consumption, are analyzed in relation to fluctuations in gasoline prices. However, gasoline orders can also change due to various non-price factors. Therefore, to understand the trend of gasoline orders, it is important to identify additional factors that gas stations consider when determining orders. We collected 180 monthly samples of data on 167 variables. Sudden international issues lead to rapid fluctuations in gasoline orders, which can lead to outliers. A class imbalance occurs because outliers are generally fewer in number than the normal data points. Therefore, to address the class imbalance, we proposed a method that grouped the data samples into 11 clusters using the K-means clustering algorithm and then augmented the data into 85 datasets in each cluster through the Variational Auto-Encoder. We evaluated the augmented datasets through the R-Squared, Root Mean Squared Errors, and accuracy of various regression models. Based on the experimental results, when predicting gasoline orders at gas stations in South Korea using augmented datasets, linear regression showed the best performance. [ABSTRACT FROM AUTHOR]

The rate of people suffering from sleep disorders has been continuously increasing in recent years, such that interest in healthy sleep is also naturally increasing. Although there are many health-care industries and services related to sleep, specific and objective evaluation of sleep habits is still lacking. Most of the sleep scores presented in wearable-based sleep health services are calculated based only on the sleep stage ratio, which is not sufficient for studies considering the sleep dimension. In addition, most score generation techniques use weighted expert evaluation models, which are often selected based on experience instead of objective weights. Therefore, this study proposes an objective daily sleep habit score calculation method that considers various sleep factors based on user sleep data and gait data collected from wearable devices. A credit rating model built as a logistic regression model is adapted to generate sleep habit scores for good and bad sleep. Ensemble machine learning is designed to generate sleep habit scores for the intermediate sleep remainder. The sleep habit score and evaluation model of this study are expected to be in demand not only in health-care and health-service applications but also in the financial and insurance sectors. [ABSTRACT FROM AUTHOR]

Proton irradiation-induced effects on AlGaN/GaN high electron mobility transistors (HEMTs) were studied by emulating a certain space radiation environment (upstream of the earth's bow shock) using a relatively low energy (100 keV) proton beam with fluences of 1 × 1010, 1 × 1012, and 1 × 1014 protons/cm2. In order to isolate radiation-induced effects produced by the modification of the epi-layer from the effects produced by the change in the device structure (such as contacts), the epi-layers were irradiated prior to device fabrication, followed by material/device characterization. Proton irradiation-induced sub-gap traps were detected by spectroscopic photo current-voltage measurement. Raman study revealed that the proton irradiation had induced strain relaxation on the AlGaN/GaN HEMTs epi-layer. No substantial change in the crystal quality of the epi-layer was indicated by Raman and PL studies. With increasing proton fluences, increasing charge carrier density was observed, which was estimated via Raman spectroscopy and the charge-control model analysis. The magnitude and direction of the transistor threshold voltage shift were also dependent on proton fluence. Overall, degradation of transistor output characteristics of the fabricated HEMTs was observed with increasing proton fluence. However, based on the observed performance and the level of influence on material/device characteristics by 100 keV protons, it can be suggested that the AlGaN/GaN HEMTs have high endurance for exposure to relatively high fluences of the low-energy proton beam. [ABSTRACT FROM AUTHOR]

Lifelogs are generated in our daily lives and contain useful information for health monitoring. Nowadays, one can easily obtain various lifelogs from a wearable device such as a smartwatch. These lifelogs could include noise and outliers. In general, the amount of noise and outliers is significantly smaller than that of normal data, resulting in class imbalance. To achieve good analytic accuracy, the noise and outliers should be filtered. Lifelogs have specific characteristics: low volatility and periodicity. It is very important to continuously analyze and manage them within a specific time. To solve the class imbalance problem of outliers in weight lifelog data, we propose a new outlier generation method that reflects the characteristics of body weight. This study compared the proposed method with the SMOTE-based data augmentation and the GAN-based data augmentation methods. Our results confirm that our proposed method for outlier detection was better than the SVM, XGBOOST, and CATBOOST algorithms. Through them, we can reduce the data imbalance level, improve data quality, and improve analytics accuracy. [ABSTRACT FROM AUTHOR]

Body mass index (BMI) plays a vital role in determining the health of middle-aged people, and a high BMI is associated with various chronic diseases. This study aims to identify important lifelog factors related to BMI. The sleep, gait, and body data of 47 middle-aged women and 71 middle-aged men were collected using smartwatches. Variables were derived to examine the relationships between these factors and BMI. The data were divided into groups according to height based on the definition of BMI as the most influential variable. The data were analyzed using regression and tree-based models: Ridge Regression, eXtreme Gradient Boosting (XGBoost), and Category Boosting (CatBoost). Moreover, the importance of the BMI variables was visualized and examined using the SHapley Additive Explanations Technique (SHAP). The results showed that total sleep time, average morning gait speed, and sleep efficiency significantly affected BMI. However, the variables with the most substantial effects differed among the height groups. This indicates that the factors most profoundly affecting BMI differ according to body characteristics, suggesting the possibility of developing efficient methods for personalized healthcare. [ABSTRACT FROM AUTHOR]

Solution-based bottom-gate zinc oxide thin film transistors (TFTs) were fabricated, remaining functional and demonstrating stability under extreme gamma irradiation conditions. Unpassivated TFTs were fabricated on samples with different number of ZnO layers grown via sol-gel spin coating technique. The devices were characterized before and after exposure to a cumulative dose of 220 MRad (air) of gamma irradiation. Atomic force microscopy (AFM), x-ray diffraction (XRD), and photoluminescence (PL) were employed to characterize the TFT active layers. Thickness measurements and optical images suggest the removal of the channel surface, conceivably due to cumulative effect of displacement damage near the ZnO surface. Device electrical characteristics were extracted from current–voltage measurements. The impact of displacement damage on the degradation/enhancement of device characteristics as a consequence of surface/bulk effects is discussed. [ABSTRACT FROM AUTHOR]

We have studied the effects of gamma radiation on flexible superconducting microstrip transmission line structures, to explore their suitability for use in harsh environments where they may be subjected to radiation. In this work, we used two conductor variants: one with only Nb and another with a conductor stack of Al/Nb/Al. Spin-on polyimide HD-4110 was used as the dielectric substrate and both the variants were encapsulated with a layer of HD-4110 to increase the robustness of the structure by protecting the superconducting trace from potential mechanical damage. The resonators were irradiated at room temperature in a vacuum sealed chamber at a pressure of 1E-6 Torr using cobalt-60 as a source of gamma radiation. Samples were exposed to doses up to 60.8 Mrad (608 kGy). Quality factors of the resonators were extracted in the frequency range from 2 to 20 GHz, at various cryogenic temperatures between 1.2 K and 4.2 K, using a closed-cycle cryostat. We observed a small increase in microwave loss for higher temperature ranges, which points to a small change in the superconducting properties of the conductors. The results of this work show that low mass, flexible superconducting cables may be suitable alternatives to bulky coaxial cables for signal transmission at cryogenic temperatures in extreme (radiation) environments. [ABSTRACT FROM AUTHOR]

The stability and reliability of emerging two-dimensional (2D) quantum materials subjected to harsh environments, such as high-energy radiation, are of high importance, particularly in the fields of space, defense, and energy applications. In this work, we explored the effects of gamma radiation on the structural and optical properties of monolayer WSe2 and WS2 crystals. Raman and photoluminescence spectroscopies were employed to study and probe radiation-induced changes to the samples after exposure to intense gamma radiation (from a 60Co source) in a high-vacuum environment (∼1 × 10−6 Torr) and with various exposure times to vary the total accumulated dosage (up to ∼56 Mrad). In general, very small changes in optical or vibrational properties were observed compared to pristine samples, suggesting noteworthy stability even for high dosages of gamma radiation. Moreover, we found that WSe2 monolayer samples exhibited higher tolerance to gamma radiation compared to WS2 samples. These findings highlight the inherent stability of these 2D quantum materials in harsh radioactive environments, which motivates further investigation of their optical, electrical, and structural properties and exploration for use in future space, energy, and defense applications. [ABSTRACT FROM AUTHOR]

The articulator is a prerequisite device for the analysis of occlusion and prosthodontic treatment, and it is required to simulate patient jaw movements. This article describes the technique to obtain sagittal condylar inclination (SCI) using cone beam computed tomography (CBCT) data and intraoral scan of the protrusive interocclusal position. The SCI can be used on a virtual articulator in a computer‐aided design software, and it can assist in the fabrication of prosthesis which is harmonious with the mandibular movement of individual patient. [ABSTRACT FROM AUTHOR]

The electronic properties of vertically aligned ZnO nanorods have been investigated using micro-Raman spectroscopy. The concentration and mobility of the charge carriers were determined via Raman line shape analysis using longitudinal-optical-phonon-plasmon coupled mode. The local laser heating and the stress effects have been considered when analyzing the Raman spectra. The mobility and carrier concentration of the aligned ZnO nanorods are 84.8 cm2/V s and 3.8×1017 cm-3, respectively. As a comparison, the mobility and carrier concentration of the undoped bulk ZnO were also obtained from the Raman line shape analysis. The mobility of the aligned ZnO nanorods is about 20% lower than that of the undoped bulk ZnO, which can be attributed to enhanced surface scattering due to the reduction in dimension. [ABSTRACT FROM AUTHOR]

The temperature-dependent electrical characteristics of Schottky rectifiers fabricated with a SiO2 field plate on a freestanding n- gallium nitride (GaN) substrate were reported in the temperature range of 298–473 K. The Schottky barrier heights evaluated from forward current-voltage measurement revealed an increase of Schottky barrier height and series resistance but a decrease of ideality factor (n) with increasing temperature. However, the Schottky barrier heights evaluated from capacitance-voltage measurement remained almost the same throughout the temperature range measured. The Richardson constant extrapolated from ln(J0/T2) vs 1/T plot was found to be 0.029 A cm-2 K-2. A modified Richardson plot with ln(J0/T2) vs 1/nT showed better linearity, and the corresponding effective Richardson constant was 35 A cm-2 K-2. The device showed a high reverse breakdown voltage of 560 V at room temperature. The negative temperature coefficients were found for reverse breakdown voltage, which is indicative of a defect-assisted breakdown. [ABSTRACT FROM AUTHOR]

The effect of hydrogen dilution on the optical properties of a wide band gap amorphous semiconductor (a-Si:C:H) was investigated. The samples were prepared by glow discharge decomposition of tetramethylsilane and were characterized primarily by optical techniques: spectroscopic ellipsometry, Raman scattering, infrared absorption, spectrophotometry, and UV photoluminescence. The deposition rate decreased with hydrogen dilution, while the silicon to carbon ratio remained constant with the addition of hydrogen. The optical band gap of this material increased as the hydrogen flow rate increased. Infrared absorption studies show that the concentration of hydrogen which is bonded to carbon decreases systematically upon hydrogen dilution. Hydrogen dilution appears to reduce the size and concentration of sp[sup 2] bonded carbon clusters, possibly caused by the etching of sp[sup 2] clusters by atomic hydrogen. The result was also supported by the shift of the Raman G peak position to a lower wave number region. Room temperature photoluminescence in the visible spectrum was observed with UV excitation. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]