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The use of virtual reality (VR) in the treatment of psychiatric disorders is increasing, and cybersickness has emerged as an important obstacle to overcome. However, the clinical factors affecting cybersickness are still not well understood. In this study, we investigated clinical predictors and adaptation effect of cybersickness during VR application in highly stressed people. Eighty-three healthy adult participants with high stress level were recruited. At baseline, we conducted psychiatric, ophthalmologic, and otologic evaluations and extracted physiological parameters. We divided the participants into two groups according to the order of exposure to VR videos with different degrees of shaking and repetitively administered the Simulator Sickness Questionnaire (SSQ) and the Fast Motion sickness Scale (FMS). There was no significant difference in changes in the SSQ or the FMS between groups. The 40–59 years age group showed a greater increase in FMS compared to the 19–39 years age group. Smoking was negatively associated with cybersickness, and a high Positive Affect and Negative Affect Schedule score was positively associated with cybersickness. In conclusion, changing the intensity of shaking in VR did not affect cybersickness. While smoking was a protective factor, more expression of affect was a risk factor for cybersickness.

The growth of artificial intelligence leads to a computational burden in solving non-deterministic polynomial-time (NP)-hard problems. The Ising computer, which aims to solve NP-hard problems faces challenges such as high power consumption and limited scalability. Here, we experimentally present an Ising annealing computer based on 80 superparamagnetic tunnel junctions (SMTJs) with all-to-all connections, which solves a 70-city traveling salesman problem (TSP, 4761-node Ising problem). By taking advantage of the intrinsic randomness of SMTJs, implementing global annealing scheme, and using efficient algorithm, our SMTJ-based Ising annealer outperforms other Ising schemes in terms of power consumption and energy efficiency. Additionally, our approach provides a promising way to solve complex problems with limited hardware resources. Moreover, we propose a cross-bar array architecture for scalable integration using conventional magnetic random-access memories. Our results demonstrate that the SMTJ-based Ising computer with high energy efficiency, speed, and scalability is a strong candidate for future unconventional computing schemes. Ising machines are promising for solving NP-hard problems, but current implementations have power consumption and scalability challenges. Si et al. implement an Ising machine consisting of 80 superparamagnetic tunnel junctions with all-to-all connections and apply it to a large-scale travelling salesman problem.

PurposeThis study was performed to investigate the prevalence of and factors associated with depressive symptoms in the Korean adult population.Methods10,710 participants in the 2014 and 2016 Korea National Health and Nutrition Examination Survey (KNHANES) were analyzed in this study. Assessment of depressive symptoms was performed using the self-administered nine-item Patient Health Questionnaire (PHQ–9).ResultsThe weighted prevalence of clinically relevant depression (PHQ-9 score ≥ 10) in the Korean adult population was 6.1% [5.5–6.8%]. Female sex, adults aged 19–29 years, elementary school graduation, living alone were significantly associated with clinically relevant depression. Having a household income ≤ 24th percentile was associated with a 2.26 (CI 1.49–3.45, p < 0.001)-fold higher prevalence of clinically relevant depression compared to having a household income ≥ 75th percentile. Regarding occupation, treating managers and professionals as controls, we found that unemployed individuals (OR 2.36, 95% CI 1.52–3.65, p < 0.001) had an increased risk of clinically relevant depression. Alcohol consumption < 30 g/day was reversely associated with clinically relevant depression (OR 0.75, 95% CI 0.62–0.93, p = 0.007), when abstain from alcohol was treated as control. Current smokers (OR 3.42, 95% CI 2.54–4.60, p < 0.001) and ex-smokers (OR 1.73, 95% CI 1.24–2.42, p = 0.001) had a higher risk of clinically relevant depression than never-smokers.ConclusionsThe estimated prevalence of depressive symptoms in a representative sample of the Korean adult population was 6.1%. This study suggests that younger age, female sex, elementary school graduation, living alone, low household income, current smoking, and being unemployed are associated with depressive symptoms.

To reduce the social burden of knee osteoarthritis (OA) by addressing it in the early stages in the population at greatest risk, the epidemiology of knee OA needs to be understood and associated demographic factors need to be identified. We evaluated the weighted prevalence of and demographic factors associated with radiographic knee OA in Korean adults. We analyzed data from 12,287 individuals aged ≥ 50 years who had radiographs of the knee taken in the 2010-2013 Korea National Health and Nutrition Examination Survey (KNHANES). Radiographic knee OA was defined based on the Kellgren-Lawrence grade, as follows: 0: No abnormal finding 1: Mild degenerative changes, minute osteophytes 2: Mild knee OA, definite osteophytes 3: Moderate knee OA, moderate joint-space narrowing and definite osteophytes 4: Severe knee OA, severe joint-space narrowing with subchondral sclerosis. We found that the prevalence of radiographic knee OA in the Korean adult population was 35.1%. Logistic regression analyses were performed to identify factors associated independently with radiographic knee OA, with age, sex, area of residence, education level, household income, and obesity serving as covariates. Women were at greater risk than men of having knee OA (OR 2.12, 95% CI 1.90-2.37, p < 0.001). Compared with subjects aged 50-59 years, adults aged ≥ 80 years were at 8.87-fold (95% CI 7.12-11.06, p < 0.001) greater risk of having knee OA. Residence in a rural area was associated with a greater risk of having radiographic knee OA than was residence in an urban area (OR 1.26, 95% CI 1.08-1.48, p = 0.004), regardless of knee OA severity (Kellgren-Lawrence grades ≥2, ≥3, and 4). Elementary school graduates had 1.71-fold (p < 0.001) greater risks of having knee OA than did college graduates. Household incomes ≤24th percentile were associated with a greater risk of having knee OA compared with those ≥75th percentile (OR 1.28, 95% CI 1.08-1.52, p = 0.004). Obesity was associated with an approximately two-fold greater risk of knee OA, regardless of knee OA severity (Kellgren-Lawrence grades ≥2, ≥3, and 4). Using data from the 2010-2013 KNHANES and defining knee OA as Kellgren-Lawrence grade ≥ 2, we found that the prevalence of radiographic knee OA was 35.1% (24.4% in men, 44.3% in women) in a representative sample of Korean adults aged ≥ 50 years, with the highest prevalence (78.7%) observed in women aged ≥ 80 years. Low socioeconomic status and traditional factors, including age, female sex, and obesity, were associated with the risk of knee OA.

The consequences of alcohol consumption on health outcomes are largely determined by two separate, but related, dimensions of drinking: the total volume of alcohol consumed and the pattern of drinking. Most epidemiological studies focus on the amount of alcohol consumed and do not consider the pattern of drinking. This study evaluated the prevalence of and factors associated with high-risk and heavy alcohol drinking in Korean adults. This study analyzed 15,215 of the 28,009 participants in the 2009-2011 Korea National Health and Nutrition Examination Survey (KNHANES). High-risk alcohol drinking was defined as Alcohol Use Disorders Identification Test (AUDIT) scores ≥16, which provides a framework for intervention to identify hazardous and harmful drinking patterns as the cause of alcohol-use disorders, according to World Health Organization guidelines. The prevalence of high-risk drinking was 15.1%, with the highest prevalence of 17.2% in middle-aged adults (45-64 years). In men, the prevalence of high-risk alcohol drinking was 23.7%, with the highest prevalence found in middle-aged adults. In women, the prevalence of high-risk alcohol drinking was 4.2%, with the highest prevalence found in younger adults. Men had higher weighted mean AUDIT scores than women (10.0 vs. 4.0, P<0.001), and age was negatively associated with the AUDIT score (P<0.001). Elementary school graduates had higher mean AUDIT scores than senior high school (P = 0.003) or college (P<0.001) graduates. Regarding occupation, clerical support workers (P = 0.002) and service and sales workers (P<0.001) had higher mean AUDIT scores than managers and professionals. Logistic regression analyses of high-risk alcohol drinking using sex, age, education level, number of family members, household income, and occupation as covariates was performed. Women had a lower risk of high-risk alcohol drinking (odds ratio (OR) 0.14, 95% CI: 0.13-0.16, P<0.001) than men. Regarding age, compared to control subjects aged 19-29 years, adults aged 60-69 and older than 70 years had 0.67- (95% CI: 0.51-0.89, P = 0.005) and 0.29-fold (95% CI: 0.20-0.70, P<0.001) lower risks, respectively, of high-risk alcohol drinking, whereas adults aged 30-59 had an increased risk of high-risk alcohol drinking. Using elementary school graduates as controls, senior high school (OR: 0.70, 95% CI: 0.55-0.87, P = 0.002) and college (OR: 0.54, 95% CI: 0.42-0. 70, P<0.001) graduates had lower risks of high-risk alcohol drinking. Regarding occupation, compared to managers and professionals as controls, service and sales workers had a greater risk of high-risk alcohol drinking (OR: 1.36, 95% CI: 1.07-1.73, P = 0.011). The number of family members and household income did not influence high-risk alcohol drinking. In a representative sample of Korean adults, the prevalence of high-risk alcohol drinking was 15.1%, with the highest prevalence of 28.3% found in middle-aged men (45-64 years). This study suggests that younger age, male sex, low education level, and service and sales workers are at risk for a high-risk drinking pattern.

Stirling engines are the engines that convert heat energy into mechanical work. This study models a 50 W linear generator designed for integration with a Stirling engine. To develop a model, the base design of the already developed 1 kW model was used, and its size was proportionally reduced to match the stroke of the Stirling engine. By reducing the length of the 1 kW model to a length scale factor (LSF) of 0.5, the stroke level of the engine was determined. However, the radius of the LSF 0.5 linear generator model was adjusted to match the engine. After finalizing the 50 W linear generator dimensions, the model was simulated using MAXWELL v14. software to compute output power and other electrical parameters. This study also analyzed the losses of the 50 W linear generator and its phasor diagram. Later, the output values generated using MAXWELL software were compared with the results obtained using SAGE v11. software for verification. The outcome of this study was a model that achieved an output power of 50 W with an efficiency of 90% and a generator size of 96 mm. Because of its versatility, low weight, and high efficiency, it can be used in a wide range of applications. Due to its small size, it can be utilized for empowering humanoid robots, radioisotope power, space exploration, etc.

An experimental study of the control characteristics of a 1 kW class free‐piston stirling converter (FPSC) with alternating current (AC) bus controls is conducted. A performance test rig is constructed using a commercial beta‐type FPSC, and an AC bus controller that includes a tuning capacitor, a set of load resistors, and an AC power supply is developed. Experiment parameters include the tuning capacitance and load resistance for the AC bus circuit and the control voltage and control frequency for AC bus control under various head temperatures of the test FPSC. In addition, preliminary experiments under load resistance control scheme were conducted to identify the natural operational characteristics of the test FPSC without an external active control scheme and to determine the proper ranges of the experiment parameters for AC bus control. The experimental results are presented in terms of the output power, the power factor, and the thermal‐to‐electric efficiency of the FPSC with respect to the load resistance and the AC bus control parameters. In particular, the effect of the control frequency with respect to the FPSC operating frequency, as well as the influence of the alternator inductance on the control characteristics of FPSC are discussed in detail. Finally, it is anticipated that this research will yield a better physical understanding of comprehensive AC bus parameters related to the performance of FPSCs, will provide a simple and accurate control method for laboratory experiments on FPSCs, and will provide fundamental data for those who design advanced virtual tuning capacitor controllers.

We propose the financial generative adversarial network–bidirectional long short-term memory (FINGAN-BiLSTM) model to accurately reproduce the complex statistical properties and stylized facts, namely, heavy-tailed behavior, volatility clustering, and leverage effects observed in the log returns of the foreign exchange (FX) market. The proposed model integrates a bidirectional LSTM (BiLSTM) into the conventional FINGAN framework so that the generator, discriminator, and predictor networks simultaneously incorporate both past and future information, thereby overcoming the information loss inherent in unidirectional LSTM architectures. Experimental results, assessed using metrics such as the Kolmogorov–Smirnov statistic, demonstrate that FINGAN-BiLSTM effectively mimics the distributional and dynamic patterns of actual FX data. In particular, the model significantly reduces the maximum cumulative distribution discrepancy in assets with high standard deviations and extreme values, such as the Canadian dollar (CAD) and the Mexican Peso (MXN), while precisely replicating dynamic features like volatility clustering and leverage effects, thereby outperforming conventional models. The findings suggest that the proposed deep learning–based forecasting model holds significant promise for practical applications in financial risk assessment, derivative pricing, and portfolio optimization, and they highlight the need for further research to enhance its generalization capabilities through the integration of exogenous economic variables.

A limited number of epidemiological studies have investigated the association between serum uric acid and pulmonary function in the general population. However, the results have been inconclusive. This study was performed to investigate the association between serum uric acid and spirometric pulmonary function in general population. Among the 8,150 participants who participated in the 2016 Korea National Health and Nutrition Examination Survey, 2,901 participants were analyzed in this study. Subjects were divided into four groups according to forced vital capacity (FVC)% predicted or forced expiratory volume in 1 second (FEV1) % predicted quartiles. Participants in the lowest quartile of FVC % predicted and FEV1% predicted were compared to those in the remaining quartiles according to age, education level, household income, smoking status, alcohol consumption, aerobic exercise, obesity, hypertension, diabetes, renal impairment, serum uric acid, and hyperuricemia. Multivariable logistic regression analyses were used to calculate the odds ratio (OR) of hyperuricemia for participants in the lowest quartile of FVC% and FEV1 predicted, with above covariates. In women, hyperuricemia was associated with lowest quartile of FVC% predicted (OR 1.71, 95% CI 1.06-2.75, p = 0.027) and FEV1 predicted (OR 1.70, 95% CI 1.06-2.74, p = 0.028) respectively, serving as above confounding variables. In men, hyperuricemia (OR 1.54, 95% CI 1.07-2.22, p = 0.021) was associated with the lowest quartile of FEV1% predicted, not FVC% predicted. According to median age, in women, age ≥ 56 years old with hyperuricemia was associated with lowest quartile of FVC% predicted (OR 1.85, 95% CI 1.04-3.28, p = 0.037) and FEV1% predicted (OR 1.99, 95% CI 1.11-3.75, p = 0.021), respectively. In men, age ≥ 56 years old with hyperuricemia was associated with lowest quartile of FEV1% predicted (OR 1.75, 95% CI 1.05-2.94, p = 0.033), not FCV% predicted. Hyperuricemia was associated with lowest quartile of FEV1% or FVC% predicted in Korean general population. This correlation between hyperuricemia and low pulmonary function was more pronounced in women and older age.

Clinical hyper and hypothyroidism are associated with a risk for depression. This study was performed to investigate the association between depressive symptoms and subclinical thyroid dysfunction. Among the 7,550 subjects who participated in the 2014 Korea National Health and Nutrition Examination Survey, 1,763 participants without overt thyroid disease were included in this study. Serum thyroid stimulating hormone (TSH), serum free thyroxine (fT4), and depressive symptoms were analyzed based on the Patient Health Questionnaire (PHQ9). The percentages of subjects with subclinical hypothyroidism and subclinical hyperthyroidism were 3.3% and 2.6%, respectively. The percentages of subjects with moderate (10-14 points), moderately severe (15-19 points), and severe (≥20 points) depression according to the distribution of PHQ-9 scores were 4.7%, 1.1%, and 0.3%, respectively. TSH, fT4, and the percentage of patients with subclinical hypothyroidism were not significantly associated with PHQ-9 score. However, the percentage of patients with subclinical hyperthyroidism increased significantly with PHQ9 score (P = 0.002). Subjects with subclinical hyperthyroidism had higher PHQ-9 scores than those with normal thyroid function (mean ± standard error [SE], 4.2 ± 0.5 vs. 2.7 ± 0.1 points, P = 0.010). More subjects with subclinical hyperthyroidism had a PHQ9 score ≥ 10 than did those with normal thyroid function (mean ± SE, 17.1 ± 3.5 vs. 5.8 ± 0.6%, P = 0.005). We performed logistic regression analyses for the presence of depressive symptoms, using age, sex, education, household income, alcohol drinking, smoking, diabetes, cerebrovascular disease history, subclinical hypothyroidism, and subclinical hyperthyroidism as variables. Subclinical hyperthyroidism was associated with the presence of clinically relevant depression (PHQ9 score ≥ 10), (odds ratio [OR], 4.04; 95% confidence interval [CI], 1.75-9.31; P = 0.001), and clinically significant depression (PHQ9 score ≥ 15), (OR, 7.05; 95% CI, 1.67-29.67; P = 0.008), respectively. However, subclinical hypothyroidism was not associated with the presence of clinically relevant depression (OR, 1.15; 95% CI, 0.39-3.38; P = 0.800), or clinically significant depression (OR, 3.35; 95% CI, 0.71-15.79; P = 0.127). We demonstrated that subclinical hyperthyroidism was independently associated with depressive symptoms in the Korean general population using national cross-sectional data.