THE PROBLEMS OF FIT INDICES ON REPLICATED SEM STUDIES

There has been a research gap in examining fit indices under the context of reproducing the result of structural equation modeling (SEM) since a replication attempt revisited not many SEM studies. Two simulation studies were conducted to examine the distribution of fit indices of SEM on replicated samples. The first simulation chose three examples from social science literature to mimic replication attempts and found that the distribution of some indices shifted away from the original value. Specifically, the fit indices that use chi-square in their formulation consistently indicated a worse fit between the model and the data in a large proportion of replication attempts. Meanwhile, relative fit indices that use log-likelihood values such as AIC and BIC were less affected by replication, showing the distribution of replicated indices centered around the value from the original sample. The chi-squared family of fit indices showed an inferior fit than the original when one tries to replicate data using the observed moment matrix, even if the model fitted well to the original data. Using a baseline model log-likelihood, a new likelihood ratio LR0 that resists the fit-worsening effect of replications is suggested. The second simulation that varied model specification, model complexity, and sample size confirmed the finding from the first study and examined the performance of the LR0. The new likelihood ratio was much less affected by replication than the standard likelihood ratio, but its interpretability was limited. The diminishing effect on fit indices in replicated samples implies that one should interpret them carefully

All but One: Surgical Concept Erasing with Model Preservation in Text-to-Image Diffusion Models

Text-to-Image models such as Stable Diffusion have shown impressive image generation synthesis, thanks to the utilization of large-scale datasets. However, these datasets may contain sexually explicit, copyrighted, or undesirable content, which allows the model to directly generate them. Given that retraining these large models on individual concept deletion requests is infeasible, fine-tuning algorithms have been developed to tackle concept erasing in diffusion models. While these algorithms yield good concept erasure, they all present one of the following issues: 1) the corrupted feature space yields synthesis of disintegrated objects, 2) the initially synthesized content undergoes a divergence in both spatial structure and semantics in the generated images, and 3) sub-optimal training updates heighten the model's susceptibility to utility harm. These issues severely degrade the original utility of generative models. In this work, we present a new approach that solves all of these challenges. We take inspiration from the concept of classifier guidance and propose a surgical update on the classifier guidance term while constraining the drift of the unconditional score term. Furthermore, our algorithm empowers the user to select an alternative to the erasing concept, allowing for more controllability. Our experimental results show that our algorithm not only erases the target concept effectively but also preserves the model's generation capability.Comment: Main paper with supplementary material

Electromyographic analysis of lower extremity muscle activities during modified squat exercise: Preliminary study

The squat is a movement that keeps the knee angle at 90° while keeping the weight of the one's shoulder to the shoulder width and maintaining equal weight load on the left and right legs. However, sufficient muscle activation of the lower limb is necessary to maintain a knee angle of 90 degrees. Thus, this study has been conducted to confirm the possibility that a modified squat exercise compared to traditional squat exercise can be recommended for elderly or patients. Two healthy adult males participated in this study. They performed a traditional squat exercise and a modified squat exercise. The modified squat exercise was performed in a general squat exercise posture while keeping the knee at 90 degrees and extending the hip joint with leaning the ball behind the back (supine position). The muscle activity of rectus femoris, vastus medialis, vastus lateralis, and gastrocnemius during exercises was measured by surface electromyography. As a result of this study, it was found that muscle activities were less in the right and left rectus femoris, vastus lateralis, vastus medialis during the modified squat exercise compared to the traditional squat exercise. The results showed that the muscle strength of the lower limb was activated to less than 50% compared with the traditional squat exercise during the modified squat exercise. These results may be used as an effective rehabilitation method for patients with weak muscles in the lower limb

Stress Estimation Using Digital Image Correlation with Compensation of Camera Motion-Induced Error

Measurement of stress levels from an in-service structure can provide important and useful information regarding the current state of a structure. The stress relaxation method (SRM) is the most conventional and practical method, which has been widely accepted for measuring residual stresses in metallic materials. The SRM showed strong potential for stress estimation of civil engineering structures, when combined with digital image correlation (DIC). However, the SRM/DIC methods studied thus far have practical issues regarding camera vibration during hole drilling. To minimize the error induced by the camera motion, the imaging system is installed at a distance from the specimen resulting in the low pixel density and the large extent of the inflicted damage. This study proposes an SRM/DIC-based stress estimation method that allows the camera to be removed during hole drilling and relocated to take the after-drilling image. Since the imaging system can be placed as close to the specimen as possible, a high pixel density can be achieved such that subtle displacement perturbation introduced by a small damage can be acquired by DIC. This study provides a detailed mathematical formulation for removing the camera relocation-induced false displacement field in the DIC result. The proposed method is validated numerically and experimentally

The government R&D funding and management performance: The mediating effect of technology innovation

Korea's small- and medium-sized enterprises are desperate to improve their performance through engaging in technological innovation, due to the fierce competition prevalent in a low growth economic environment. However, most small- and medium-sized enterprises are having difficulty responding to changes in the economic environment due to the challenge of developing their own technologies and their limited resources. The aim of this study is to assess whether government financial support for R&D aimed at small- and medium-sized enterprises has contributed to improvements in their business management performance. The sample of this study was comprised of 105 KOSDAQ-listed small- and medium-sized enterprises with experience in technology development. The empirical analysis was conducted on the basis of the mediating effect measurement method of Baron and Kenny (1986). It was found that company technological innovation capabilities have a positive effect on management performance, and in particular, that the majority of companies that received government financial support for R&D have improved their management performance. Therefore, it is recommended that small- and medium-sized companies take an active part in various government R&D financial support programs and make efforts to strengthen their technological innovation in areas such as their product service and process innovation capabilities

Serviceability Assessment Method of Stay Cables with Vibration Control Using First-Passage Probability

As the construction of long-span bridges such as cable-stayed bridges increases worldwide, maintaining bridge serviceability and operability has become an important issue in civil engineering. The stay cable is a principal component of cable-stayed bridges and is generally lightly damped and intrinsically vulnerable to vibration. Excessive vibrations in stay cables can potentially cause long-term fatigue accumulation and serviceability issues. Previous studies have mainly focused on the mitigation of cable vibration within an acceptable operational level, while little attention has been paid to the quantitative assessment of serviceability enhancement provided by vibration control. This study accordingly proposed and evaluated a serviceability assessment method for stay cables equipped with vibration control. Cable serviceability failure was defined according to the range of acceptable cable responses provided in most bridge design codes. The cable serviceability failure probability was then determined by means of the first-passage problem using VanMarcke???s approximation. The proposed approach effectively allows the probability of serviceability failure to be calculated depending on the properties of any installed vibration control method. To demonstrate the proposed method, the stay cables of the Second Jindo Bridge in South Korea were evaluated and the analysis results accurately reflected cable behavior during a known wind event and show that the appropriate selection of vibration control method and properties can effectively reduce the probability of serviceability failure

Long-term displacement measurement of full-scale bridges using camera ego-motion compensation

Civil infrastructures experience long-term deflection as a result of persistent and transitory loadings, including self-weight, pre-stress, traffic, temperature variation, and stress redistributions due to damage. Thus, long-term displacement is an important safety indicator that can be widely employed in structural health monitoring. However, its measurement is challenging because of the errors induced by the ego-motion of sensors. Researchers have attempted to compensate for the motion-induced error in computer vision-based displacement measurement methods for full-scale civil structures by using fixed objects in the background. Because remotely located objects cannot fully provide six degrees-of-freedom (6-DOF) camera motions, further developments are necessary for complete error compensation. This paper proposes a long-term displacement measurement strategy that uses computer vision-based ego-motion compensation. The proposed system consists of main and sub-cameras attached to each other. While the main camera employs the conventional computer vision-based method for displacement measurement, the sub-camera measures the ego-motions of the dual-camera system from which the motion-induced errors are estimated and compensated for. The proposed long-term displacement measurement algorithm was numerically validated, and the sub-camera was found to provide a noticeable error compensation. A laboratory-scale test showed that the motion-induced error was reduced from 44.1 mm to 1.1 mm. A field application conducted upon a newly constructed railway bridge provided continuous long-term displacement measurement data, which were consistent with LiDAR-based displacement measurements and numerical predictions. (C) 2020 Elsevier Ltd. All rights reserved