Time-varying Analysis Research Articles

Time-heterogeneous impacts of global temperature cycle on world business cycle

ABSTRACT We study the statistical relationship between the world business cycle and the global temperature cycle. To amplify the signal-to-noise ratio, we estimate a two-state latent dynamic process from the original data using the endogenous regime-switching methodology. Subsequently, we apply a time-varying structural VAR analysis to identify the time-heterogeneous relationship between the extracted latent factors. Our findings provide empirical evidence that the global mean temperature cycle has a negative impact on the world business cycle during super El Niño periods, which are characterized by relatively high temperature variance records given the past information.

Empirical insights into India's energy demand: unveiling elasticity dynamics for strategic policy initiatives.

Policymakers and stakeholders can use insights from price elasticity and income elasticities of energy demand to devise targeted interventions that promote energy efficiency, reduce reliance on fossil fuels, and drive the transition to more sustainable and resilient energy systems. This study seeks to examine how changes in income elasticity and price elasticity affect energy consumption over time using the ARDL model and a time-varying parameter technique, state-space Kalman filter. The study's findings reveal that energy prices have a negative and significant impact on energy consumption, whereas GDP per capita and population growth have apositive and significant impact on energy consumption in both the short and long run. The findings underline the importance of economic growth and increasing population in driving growing energy demand in India, which is consistent with the country's energy-intensive development aspirations. The time-varying analysis shows that the price elasticity of energy consumption follows a U-shaped pattern across time. However, from the onset of the new millennium decade, the elasticity of energy consumption with regard to its price has continually decreased, reaching - 0.54 by 2020. Furthermore, the findings imply that the income elasticity of India's energy demand has stabilized around unity, indicating that the country is currently near the middle of the energy intensity-GDP inverted-U trajectory. Given these evolving elasticities, policymakers should take a flexible and forward-thinking strategy to achieve optimal energy consumption levels.

Risk of Discontinuance in Contraceptive Uptake Among Kenya Women: A Survival Analysis Using the Cox Proportional Hazard Model

A problem of equal importance is the substantial challenge posed by the discontinuance of contraceptive use in family planning programs, particularly for developing countries such as Kenya. Investigating the determinants of contraceptive discontinuation using demographic factors can provide insights to enhance the efficacy of family planning. Using data from the Performance Monitoring for Action (PMA) survey, this study examined the demographic and contraceptive method-related covariates associated with the risk of discontinuation of contraception among Kenyan women. The study employed Cox proportional hazards models to analyze sampled data of Kenyan women from the PMA survey. Two separate models were used: a standard model which included demographic characteristics with a baseline contraceptive variable (Ever use contraceptive) and an extended model showing how specific contraceptive methods impact the likelihood of the risk of discontinuing contraception. Older age (Coefficient of -0.268 with a hazard ratio of 0.765) was associated with a decreased risk of contraceptive discontinuation. At the same time, women with higher educational levels (Coefficient of 0.015, with a hazard ratio of 1.015) were related to an elevated hazard and were more likely to discontinue their current method of contraception. The extended model showed that subcutaneous injectable contraceptives (Coefficient of -2.040 with a hazard ratio of 0.130) and male condoms (Coefficient of -1.137 with a hazard ratio of 0.321) were conditionally related to a significantly decreased hazard of discontinuation. The results highlight the importance of contraception choice and the significance of age and education in maintaining continuous contraception. To support Kenyan women in maintaining continuous contraception in achieving their reproductive health goals comprehensive education on emergency contraception and the provision of long-acting reversible contraceptives should be provided by health and family planning organizations. There is a call for a longitudinal study to offer an understanding of the dynamic behavior of contraception over time and the need for time-varying analyses to capture the evolving nature of contraception and its discontinuation.

High-frequency whole blood donation and its impact on mortality: Evidence from a data linkage study in Australia.

Previous reports suggest that blood donors have a lower mortality risk, which may partially reflect the "healthy donor effect" (HDE). HDE arises in donors due to selection bias and confounding if not appropriately addressed. Using the Sax Institute's 45 and Up Study data linked with blood donation history, we used a "5-year exposure window" method to select donors into regular high-frequency whole blood (WB)donors (at least two donations per exposure year) and low-frequency donors (remaining donors) with an active donation career of 5 years. To further reduce the confounding, we used statistical approaches like the inverse probability weighted (IPW) marginal structural model and the doubly robust targeted minimum loss-based estimator (TMLE), which incorporated machine learning algorithms and time-varying analyses. We selected 4750 (64.7%) low-frequency and 2588 (35.3%) high-frequency donors in the analyses. A total of 69 (1.5%) from the low-frequency and 45 (1.7%) donors from the regular high-frequency group died during the 7-year follow-up period. We did not find any statistically significant association between regular high-frequency blood donation and mortality (IPW RR = 0.98 95% CI 0.68, 1.28). TMLE model also showed similar results to IPW (RR = 0.97 95% CI 0.80, 1.16). Time-varying TMLE did not find any significant association between high-frequency donation and all-cause mortality either (RR = 0.98 95% 0.74, 1.29). We did not find a significant association between regular high-frequency WB donation and all-cause mortality when appropriate methods were employed to minimize the HDE.

Transverse Vibration Response and Time-Varying Analysis of Axially Moving Beams Based on Choi–Williams Distribution

Cantilever beams with axial extension and contraction functions as time-varying parameter systems have attracted extensive research due to their prevalence in engineering structures. In this paper, the dynamic characteristics of the flat-push bridge mechanism are investigated from the theoretical aspect, firstly, it is simplified into a cantilever beam model with axial motion, and the transverse vibration equations of the cantilever beam are established based on the Euler–Bernoulli beam theory and D’Alembert’s principle, and the transverse displacements of the beam are discretized using the Galerkin truncation method and solved numerically by using the Newmark-[Formula: see text] method for the second-order vibration differential equations with variable coefficients; second-order vibration differential equations were solved numerically by the Newmark-[Formula: see text] method; then the structural examples in the existing literature are verified numerically, and the calculation results are consistent with the literature results, indicating that the transverse vibration equations derived in this paper are solved effectively; then a parametric analysis of the speed of the cantilever beam during axial extension/contraction was done, which showed that the faster the speed of axial motion, the faster the rate of change of the dynamic characteristics of the beam and the more pronounced the vibration; finally, the power signal is decomposed in the time-frequency domain by using the Choi–Williams Distribution (CWD), and the time-frequency characteristics of the system under different speeds are analyzed, and the results show that the use of CWD technique can accurately reflect the system’s transient vibration frequency and vibration energy with the change rule of time and speed, and the axial motion speed of ±0.05[Formula: see text]m/s, the transient frequency of the theoretical prediction and the average relative deviation between the finite element modal frequencies are kept within 5% and the recognition accuracy is high. This analysis provides flexible technical guidance for vibration control in engineering structures.

Time-dependent reliability analysis of flood defenses under cumulative internal erosion

Internal erosion is a significant cause of failure in dams, levees and other hydraulic structures. This article studies the time-dependent reliability of such structures under Backward Erosion Piping (BEP), a form of internal erosion in the foundation. First, a physics-based time-dependent piping failure model is presented. Second, a time-variant reliability analysis method is presented which allows to quantify how the reliability evolves over the years due to cumulative pipe growth over multiple flood events. Finally, these models are used to study the importance of time-dependence for reliability estimates of flood defenses in The Netherlands. The findings show that, particularly in coastal areas, incorporating time-dependence significantly reduces the computed failure probability. Reductions vary widely, ranging from a factor of 5 to more than 10 6 , depending on flood duration and levee properties. Therefore, reliability estimates for levees can be improved by incorporating time-dependent pipe development in the BEP failure model, and thereby contribute to avoiding unnecessary reinforcements.

Developmental trajectories and heterogeneity of social engagement among Chinese older adults: a growth mixture model

BackgroundSocial engagement is closely related to well-being among older adults. However, studies on the changing trajectory and influencing factors (especially time-varying factors) of social engagement are limited. This study aimed to examine the social engagement trajectory of older Chinese adults and explore its time-fixed and time-varying factors, thus providing evidence for the development of strategies to promote a rational implementation for healthy aging.MethodsThis study included 2,195 participants from a subset of four surveys from the Chinese Longitudinal Healthy Longevity Survey conducted from 2008 to 2018 (with the latest survey completed in 2018), with follow-ups conducted approximately every three years. Growth mixture modeling was used to explore the social engagement trajectory of older adults and the effects of time-varying variables. In addition, multinomial logistic regression was employed to analyze the association between time-fixed variables and latent classes.ResultsThree distinct trajectories of social engagement among older adults in China were identified: slow declining (n = 204; 9.3%), which meant social engagement score decreased continuously, but social engagement level improved; slow rising (n = 1,039; 47.3%), marked by an increased score of social engagement, but with an depressed engagement level; and middle stabilizing (n = 952; 43.4%), which meant social engagement score and engagement level remained quite stable. A time-fixed analysis indicated that age, marital status, educational level, and annual family income had a significant impact on social engagement (P < 0.05). In contrast, the time-varying analysis showed that a decline in functional ability, insufficient exercise (means no exercise at present), deteriorating self-reported health and quality of life, negative mood, monotonous diet, and reduced community services were closely related to the reduction in social engagement levels (P < 0.05).ConclusionThree trends were observed at the social engagement level. Older adults with initially high levels of social engagement exhibited a continuous upward trend, whereas those with initially low levels experienced a decline in their social engagement, and those with initially intermediate levels remained quite stable. Considering the primary heterogeneous factors, it is imperative for governments to enhance basic services and prioritize the well-being of older adults. Additionally, families should diligently monitor the emotional well-being of older adults and make appropriate arrangements for meals.

How Upgrading of Provincial Development Zones Reduces Urban Carbon Emission: Evidence from a Time-Varying DID Analysis

This study examines the impact of upgrading provincial development zones on urban carbon emission reduction in China, a vital policy instrument for achieving the nation’s dual objectives of economic growth and green development under the “carbon neutrality and carbon peak” framework. Utilizing panel data from 276 Chinese cities spanning 2006 to 2019, this study employs a time-varying difference-in-differences model to empirically assess the effects of these upgrades. The findings indicate that these upgrades significantly reduce urban carbon emissions through policy, agglomeration, and regulatory effects. The heterogeneity analysis further reveals that the policy’s effectiveness is amplified by higher levels of government participation, increased attention to environmental protection, and greater urban emission reduction pressures. Moreover, while the policy facilitates carbon emission reductions in neighboring cities through spatial spillover effects, it does not achieve synergistic control over multiple pollutants, showing no significant impact on other industrial pollutants emissions. These findings provide value insights for policymakers aiming to balance economic development with environmental sustainability.

An efficient single-loop strategy for time-variant reliability sensitivity analysis based on Bayes’ theorem

Time-variant reliability sensitivity analysis aims to measure the effect of input variables on the time-variant failure probability, which can then be used to guide structural design and optimization. The traditional methods for calculating the sensitivity index require a nested sampling procedure and their computational complexity depends on the number of input variables, making them computationally the most expensive. To address the above limitations, an efficient single-loop strategy is developed for time-variant reliability sensitivity (TRS) analysis. Based on Bayes' theorem, the TRS index is represented by the difference between the probability density function (PDF) and failure-conditional PDF of the variable. This derivation enables TRS analysis to be implemented using only a single set of samples, with computational costs that don’t depend on the number of input variables. Then, the sensitivity index is normalized to identify influential variables effectively. Several case studies involving numerical and engineering problems are employed to verify the feasibility and effectiveness of the proposed strategy. The direct Monte Carlo simulation is introduced to assess the accuracy of the obtained results. The results indicate that the proposed strategy provides acceptable sensitivity analysis for time-variant events, while greatly conserving computational resources and enhancing efficiency.

The advantages of CBOE credit VIXs for corporate bond investors in North America: A sectoral analysis

This paper examines the safe-haven role of the recently introduced CBOE credit VIXs for investment-grade and high-yield corporate bonds, at both aggregate and sectoral levels. Using a time-varying quantile-based framework and daily data from June 5, 2014 to December 10, 2023, the safe-haven role of credit VIX is confirmed irrespective of bond sector. The safe-haven property of credit VIX is pronounced for high-yield bonds which embed a high credit risk-premium. This result stands when taking into account interest rate volatility, as measured by the MOVE index. A time-varying analysis shows the persistence of credit VIX as a safe-haven for all bond sectors after the COVID-19 pandemic and during a high US interest-rate regime. Corporate bond investors and traders can use these findings to refine their investment and trading decisions and offset credit risk during both normal and turbulent periods.

Do Supply Chain Pressures Affect Consumer Prices in Major Economies? New Evidence from Time-Varying Causality Analysis

This study explores the dynamic causality between the consumer price index and supply chain pressure index in two large economies. Despite extensive research into the role of supply chains at the firm level, literature on their impact on time-varying inflation and macroeconomic stability is scarce. Using data from the United States and the European Union from January 2000 to December 2021, we employ novel time-varying causality techniques to examine the evolving relationships among inflation, supply chains, real gross domestic product, interest rates, and oil prices. Our findings show that supply chains have a significant dynamic relationship with consumer prices, particularly during economic crises like the 2008 global financial crisis and the COVID-19 pandemic. Robustness tests including impulse response functions and the autoregressive distributed lag model confirm this causality. These results are critical for policymakers, emphasizing the importance of supply chains in controlling inflation and achieving global economic resilience and stability.

A time-varying non-probabilistic reliability analysis method using surrogate model for the reinforcement effectiveness of damaged concrete gravity dam

Evaluation of the effectiveness of reinforcement measures for the diseased concrete gravity dam is a critical issue in the field of hydraulic structural health control. The traditional probabilistic reliability analysis method is constrained by factors such as the randomness of the uncertain parameters, the high nonlinearity of the performance function, etc., when it is applied to the evaluation of the effectiveness evolution of reinforcement measures for the diseased concrete gravity dam. Therefore, a time-varying non-probabilistic reliability (NR) analysis method is proposed in the research. To characterize the uncertainty of the parameters, we adopt the form of interval numbers to present parameters and construct the interval parameter-based reliability analysis framework. Specifically, combining interval mathematics and non-probabilistic reliability theory, the NR calculation model for the gravity dam is proposed. In addition, considering of the aging of the structure, the time-varying NR (TV-NR) calculation model utilized to evaluate the long-term reinforcement effectiveness is established. To tackle the issue of expensive computation existed in the TV-NR model, response surface method (RSM) is coupled in the TV-NR calculation model to replace the original high nonlinearity performance function. Ultimately, the proposed method is verified in engineering examples that it can detect the most possible initial locations and failure processes of the gravity dam varying with time and can efficiently and accurately evaluate the reinforcement effectiveness of the gravity dams. The results indicate that the use of reinforcement measures can provide an improvement for the safety service of gravity dams.

Is the business cycle getting hit by climate policy uncertainty in China?

This study apply an asymmetric time-varying test to assess the impact of China's climate policy uncertainty (CCPU) on its business cycle (2000–2022) using currency supply indices (M2, M1, and M0) as economic proxies. Linear Granger tests indicate no causal relationship between CCPU and the currency supply in general. However, the time-varying analysis reveals a significant impact of CCPU on M2 after December 2020. In addition, M2 mainly responds to negative CCPU shocks whereas M1 and M0 respond to both positive and negative shocks. Therefore, policymakers should adopt stabilisation measures to mitigate M2 contraction during CCPU surges while monitoring M1 and M0 for comprehensive currency policy adjustments.

Effects of the Non-Steroidal MRA Finerenone with and without Concomitant SGLT2 Inhibitor Use in Heart Failure.

Patients with heart failure (HF) with mildly reduced or preserved ejection fraction face heightened long-term risks of morbidity and mortality. The sodium glucose-co-transporter-2 inhibitors (SGLT2i) and the non-steroidal mineralocorticoid receptor antagonist (MRA) finerenone have both been shown to reduce the risk of cardiovascular events in this population, but the effects of their combined use are not known. FINEARTS-HF was a randomized, double-blind, placebo-controlled trial of finerenone in patients with HF and left ventricular ejection fraction (LVEF) ≥40%. Baseline SGLT2i use was a prespecified subgroup. The primary outcome was a composite of total (first and recurrent) worsening HF events and cardiovascular death. We first assessed for evidence of treatment heterogeneity based on baseline SGLT2i use. We further examined SGLT2i uptake during the trial and evaluated the treatment effects of finerenone accounting for baseline and during trial use of SGLT2i in time-varying analyses. Among 6,001 participants, 817 (13.6%) were treated with an SGLT2i at baseline. During 2.6-years median follow-up, treatment with finerenone similarly reduced the risk of the primary outcome in participants treated with an SGLT2i (rate ratio 0.83; 95% confidence interval 0.60 to 1.16) and without an SGLT2i at baseline (rate ratio 0.85; 95% confidence interval 0.74 to 0.98); Pinteraction=0.76. In follow-up, 980 participants initiated SGLT2i, which was less frequent in the finerenone arm compared with placebo (17.7% vs. 20.1%; hazard ratio 0.86; confidence interval 0.76 to 0.97). Time-updated analyses accounting for baseline and subsequent use of SGLT2i did not meaningfully alter the treatment effects of finerenone on the primary endpoint. The treatment benefits of the non-steroidal MRA finerenone were observed irrespective of concomitant use of an SGLT2i. These data suggest that the combined use of SGLT2i and a non-steroidal MRA may provide additive protection against cardiovascular events in patients with HF with mildly reduced or preserved ejection fraction.

Time-Varying Stability Analysis of the Trenching Construction Process of Diaphragm Wall

The stability of underground diaphragm walls is crucial for ensuring the safety and integrity of trench excavations in geotechnical engineering. This study addresses this critical issue by proposing a novel destabilization mechanism based on a sliding body model specifically designed for diaphragm wall trenching operations. The research employs an analytical framework rooted in soil mechanics and plasticity theory, utilizing limit equilibrium analysis to develop a method for calculating the minimum required slurry density and corresponding safety factor for trench stability. The study compares two distinct approaches to slurry density computation, analyzing their sensitivity to various influencing factors. Theoretical findings are validated through multiple real-world engineering case studies. Comparative analysis demonstrates the superiority of the proposed method, particularly in assessing trench stability within clay layers. Key variables influencing the safety factor are identified, including trench length, slurry density, soil friction angle, and the relative height difference between slurry and groundwater levels. Results indicate that actual slurry densities observed in practice consistently fall within the bounds predicted by the theoretical calculations. This research contributes a valuable theoretical framework to the field of diaphragm wall construction, offering improved accuracy in stability assessments and potentially enhancing safety in geotechnical engineering projects.

Iterative local maximum synchrosqueezing-extracting transform

Recently, there has been significant interest in time-varying signal analysis. Multisynchrosqueezing transform (MSST) and improved multisynchrosqueezing transform (IMSST) have shown promise in overcoming the limitations of conventional methods. Although progress has been made, challenges still exist, such as the presence of non-reassigned time–frequency (TF) points and the presence of noise in the TF plane when processing noisy time-varying signals. In this paper, we introduce an innovative TF analysis method known as the iterative local maximum synchrosqueezing-extracting transform (ILMSSTSEO). First, the proposed method extracts the local maximum value of the instantaneous frequency (IF) during each iteration to eliminate non-reassigned TF points. Additionally, a synchroextracting operator is introduced unconventionally to enhance the concentration of TF energy and reduce noise in the TF representation. By doing so, the method effectively solves many challenges faced by existing methods and provides a new extraction framework for synchrosqueezing transform-based TF analysis methods.

Public debt determinants: A time-varying analysis of core and peripheral Euro area countries

This study employs a Bayesian Interacted Panel VAR model to estimate time-varying Generalized Forecast Error Variance Decomposition, analyzing how key determinants affect debt in Core and Peripheral Euro Area countries. Results highlight varying effects of determinants across periods and subgroups.

A data-driven underground gas storage production system string failure prediction model for time-varying reliability analysis

In underground gas storage (UGS) systems, the production tubing string system undergoes complex thermo-mechanical loading conditions, leading to fatigue damage accumulation and potential failure risks. To accurately assess the fatigue reliability and mitigate risks, it is crucial to develop a data-driven physics-informed uncertainty modeling approach that captures the coupled thermo-mechanical effects and accounts for various uncertainties. This study proposes a data-driven physics-informed modeling method based on thermo-mechanical coupling for fatigue reliability assessment and risk mitigation in critical UGS systems. A quantitative analysis method is introduced, which relies on small-scale multi-stage loading experiments and combines the stochastic degradation process with time-series reliability theory. To analyze the fatigue life of joints under complex loading conditions, a modified S-N curve model is developed. This model takes into account the influences of the dimension coefficient, stress concentration factors, surface finish coefficients, and thermal load. It considers the uncertainties associated with different temperature loads and surface finish on fatigue life. By integrating physics-informed modeling, uncertainty quantification, and fatigue damage accumulation analysis, this approach provides a comprehensive framework for fatigue reliability assessment and risk mitigation in critical UGS systems. It enables informed decision-making for safe and reliable operations, as well as optimized maintenance strategies, ultimately enhancing the overall system performance and mitigating potential failures.

Provincial and connector qualities of somatosensory brain network hubs in bipolar disorder.

Brain network hubs are highly connected brain regions serving as important relay stations for information integration. Recent studies have linked mental disorders to impaired hub function. Provincial hubs mainly integrate information within their own brain network, while connector hubs share information between different brain networks. This study used a novel time-varying analysis to investigate whether hubs aberrantly follow the trajectory of other brain networks than their own. The aim was to characterize brain hub functioning in clinically remitted bipolar patients. We analyzed resting-state functional magnetic resonance imaging data from 96 euthymic individuals with bipolar disorder and 61 healthy control individuals. We characterized different hub qualities within the somatomotor network. We found that the somatomotor network comprised mainly provincial hubs in healthy controls. Conversely, in bipolar disorder patients, hubs in the primary somatosensory cortex displayed weaker provincial and stronger connector hub function. Furthermore, hubs in bipolar disorder showed weaker allegiances with their own brain network and followed the trajectories of the limbic, salience, dorsal attention, and frontoparietal network. We suggest that these hub aberrancies contribute to previously shown functional connectivity alterations in bipolar disorder and may thus constitute the neural substrate to persistently impaired sensory integration despite clinical remission.

Does an Independent Central Bank Smooth Exchange Rate Volatility? Evidence from Time-Varying Panel Causality Analysis

Abstract This paper empirically examines the effect of the central banks independence on exchange rate volatility by using a large data-set for the E7 (7 emerging countries) covering the period 1998-2017. This paper applies the time-varying panel causality analysis to obtain country-based results. The results show that the policy design, with relatively independent central banks, provides supportive results for macroeconomic stability. It is concluded that policies focusing on current problems by ignoring macroeconomic stability, such as the 2008 crisis, have eliminated the relationship between bank independence and stability.