Low Performance Research Articles

Step to the beat: Auditory-motor coupling during walking to higher and lower tempi with music and metronomes in progressive multiple sclerosis: An observational study

BackgroundMany persons with multiple sclerosis (MS) are confronted with fatigue and difficulties with walking and even more so in persons with progressive subtypes of MS. Task-oriented training, and more specifically in the form of auditory-motor coupling, where persons are asked to synchronise their steps to beats in music and metronomes, is promising. However, it is currently not known whether persons with progressive MS (PwPMS) can synchronise their steps to beats in music and metronomes and if they can adapt their gait to slower and higher tempi. MethodsThe study is a case control study where participants with progressive MS (PwPMS) and healthy controls (HCs) were asked to synchronise their steps during overground walking to beats in music and metronomes at five different tempi, ranging from slow (-8%, -4%), baseline (0%) and high (4%, 8%) while synchronisation, spatiotemporal parameters and gait dynamics were recorded. Mixed model analyses were performed on synchronisation outcome measures and spatiotemporal gait parameters. Additionally, a regression analysis was performed to identify clinical factors such as cognition and motor function influencing synchronisation consistency. ResultsIn total, 18 PwPMS (mean age = 52.4, median EDSS = 4.24) and 16 healthy controls (HCs) (mean age = 56.5) were included in the study. Results show that both groups were able to synchronise their steps to beats in music and metronomes, but highest synchronisation consistency was reached for metronome conditions compared to music conditions and for HCs compared to persons with progressive MS. Highest synchronisation consistency for persons with progressive MS was found at -4% and 0%. Additionally, more variability in inter-step-intervals and thus a more anti-persistent gait pattern was found for metronome compared to music conditions. Last, lower performance on the Timed Up & Go Test negatively impacted synchronisation consistency. ConclusionPwPMS are able to synchronise steps to beats in music and metronomes. Overall, more consistent synchronisation is seen for metronome conditions. All participants are able to adapt their cadence to all tempi, yet, PwPMS struggle to adapt gait speed to high tempi. Noteworthy, participants walk with more random inter-step-interval fluctuations when walking to metronome compared to music conditions. Last, dynamic balance significantly impacted synchronisation consistency. These results show the potential of using auditory-motor coupling for walking related rehabilitation for PwPMS, however, tempo and auditory stimulation should be carefully considered.

Polytope Fraud Theory

Polytope Fraud Theory (PFT) extends the existing triangle and diamond theories of accounting fraud with ten abnormal financial practice alarms that a fraudulent firm might trigger. These warning signals are identified through evaluation of the shorting behavior of sophisticated activist short sellers, which are used to train several supervised machine learning methods in detecting financial statement fraud using published accounting data. Our contributions include a systematic manual collection and labeling of companies that are shorted by professional activist short sellers. We also combine well-known asset pricing factors with accounting red flags in financial features selections. Using 80 % of the data for training and the remaining 20 % for out-of-sample test and performance assessment, we find that the best method is XGBoost, with a Recall of 72 % and F1-score of 82 %. Other methods have relatively lower performance, demonstrating the robustness of our results. This shows that the sophisticated activist short sellers, from whom the algorithms are learning, have excellent accounting insights, tremendous forensic analytical knowledge, and sharp business acumen. Our feature importance analysis indicates that potential short-selling targets share many similar financial characteristics, such as bankruptcy or financial distress risk, clustering in some industries, inconsistency of profitability, high accrual, and unreasonable business operations. Our results imply the possible automation of advanced financial statement analysis, which can both improve auditing processes and effectively enhance investment performance. Finally, we propose the Unified Investor Protection Framework, summarizing and categorizing investor-protection related theories from the macro-level to the micro-level.

Does online education magnify educational inequalities? Evidence from the COVID-19 pandemic

Taking the closure of all primary and secondary schools in China at the start of the COVID-19 pandemic as a quasi-natural experiment, this paper examines the impact of online education on student academic performance and the role of family socioeconomic status (SES) in the K-12 online environment. We employ a difference-in-differences approach and find that online learning has a positive effect on the performance of previous high-achieving students and a negative effect on low-achieving students. Further, employing the difference-in-difference-in-differences method, we find that students from high-SES families improve their GPA by 0.464 points after distance learning relative to disadvantaged students, i.e., the gap between low and high SES performance widens by 16.7 %, and this effect is more pronounced among students in primary schools and in provinces where online education lasts longer. The mechanism analysis shows that high-SES families help their children make academic progress in online education by developing their children's academic locus of control, providing access to information and communication technology, and increasing study time.

Improved ionic conductivity of La and Mg co-doped ceria nanocrystals synthesized by auto-combustion method

Ionic conductivity of La3+ and Mg2+ co-doped ceria, synthesized by auto-combustion method, is investigated here as electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFCs, operating below 800 °C). The prepared nanocrystalline electrolytes, LMDC10 (Ce0.9La0.05Mg0.05O2-δ) and LMDC20 (Ce0.8La0.1Mg0.1O2-δ) have exhibited improved ionic conductivities of 1.31 × 10−2 and 1.39 × 10−1 S cm−1 at 1073 K with reduced activation energies of 0.93 and 0.97 eV, respectively, when compared to conventional electrolytes like yttria-stabilized zirconia. The prepared samples are characterized by XRD, Raman spectra, XPS and FESEM which confirmed the formation of single-phasic cubic fluorite structure. Thus, the potential for La3+ and Mg2+ co-doped ceria electrolytes to offer cost-effective alternatives with low sintering temperatures and high performance for IT-SOFCs.

Entrepreneurial finance and sustainability: Do institutional investors impact the ESG performance of SMEs?

Institutional investors improve the environmental, social, and governance (ESG) performance of small- and medium-sized enterprises (SMEs). Our difference-in-differences framework shows that the backing from private equity and venture capital funds leads to an increase in SMEs’ externally validated ESG scores compared to their matched non-investor-backed peers. Consistent with “ESG-as-insurance” theory, the ESG performance of SMEs with a higher probability of failure is more likely to benefit from the backing of institutional investors. This positive effect is heterogeneous; while SMEs with high ex-ante ESG performance further improve their ESG performance following institutional investor backing, SMEs with low ex-ante ESG performance are unlikely to implement any improvements. Entrepreneurial finance seems to help sustainable entrepreneurs transform into “sustainability champions,” while neglecting the betterment of non-sustainable SMEs.

An anti-freezing hydrogel electrolyte based on hydroxyethyl urea for dendrite-free Zn ion batteries

Aqueous zinc ion batteries are considered as a promising energy storage resource due to their high security, abundant resources and low price. However, the development of aqueous zinc ion batteries has been severely hindered by compulsive dendrite generation, serious side reactions and poor temperature adaptability. Herein, we used hydroxyethyl urea as a hydrogel electrolyte additive to address above-mentioned challenges. Hydroxyethyl urea can break the hydrogen bonds (HBs) of water and enhancing the freezing-tolerance ability of the electrolyte. Meanwhile, hydroxyethyl urea can prevent the corrosion issue and inhibition of Zn dendrites. Consequently, the Zn//Zn symmetric battery can sustain stable cycling for over 3000 h at 1 mA cm−2, and it achieves a high coulombic efficiency of 99.6 %. Even at −40 ℃ the batteries show excellent cycling stability, the Zn//Zn symmetry battery can achieve steadily cycles over 3000 h. The Zn//NVO battery equipped with the altered electrolyte exhibits enhanced capacity retention compared to the one without additives.It demonstrates not only robust stability at room temperature but also maintains commendable functionality down to −40 ℃, validating the method’s efficacy. This work provides a simple strategy for enhancing low temperature performance of zinc ion batteries.

Evaluation of pine needle oil recycled asphalt: Rheological characterization and molecular dynamics simulation

The regenerant based on bio-oil has the potential to lower carbon emissions, conserve natural resources, and shows promising prospects for application. In this paper, pine needle oil (PNO) and dioctyl phthalate (DOP) were utilized as base materials for asphalt rejuvenator. The primary aim of this research was investigate the impact of the rejuvenator on the rheological characteristics of asphalt and the compatibility between the rejuvenator and aged asphalt. The rheological properties of the asphalt were evaluated by the bending beam rheometer (BBR) and the dynamic shear rheometer (DSR). The glass transition temperature of the asphalt was tested by differential scanning calorimetry (DSC). Finally, the glass transition temperature (Tg), mean square displacement (MSD), cohesive energy density (CED), and solubility parameter (δ) were calculated and analyzed through molecular dynamics simulation to clarify the mechanism of PNO and DOP on asphalt. In the tested temperature range, the creep stiffness modulus of the PNO compound DOP recycled asphalt had decreased by 43.7∼68.4 % compared with the aged asphalt, and the rutting factor had decreased by 59.6∼75.3 %, but it was still better than the original asphalt. This showed that the regenerant had significantly restored the rheological properties of the asphalt. At 413.15 K, the difference of solubility parameters between PNO and DOP was the lowest, which was 1.37 and 0.17 (J/cm3)0.5, respectively. At this time, the compatibility between the PNO regenerant and aged asphalt was the best. The addition of the PNO softened the aged asphalt, reduced the rutting factor, adjusted the composition of the aged asphalt, improved its colloidal structure, and thereby enhanced its low temperature performance. The PNO regenerant also improved the diffusion of the four components of the aged asphalt and positively influenced the diffusion and fusion process of the system. DOP molecules lowered the asphalt's glass transition temperature, increased the amount of free space available for the thermal motion of asphalt molecules, and improved the compatibility of the asphalt with the regenerant.

Biopolymers as three-dimensional structural binders for nickel-cobalt sulfide supercapacitor electrodes

Ion diffusion and electron transfer are hindered by commonly used hydrophobic binders, which directly affect the electrochemical performance of the electrodes. Hydrophilic binders are selected to efficaciously solve the problem of relatively low actual specific capacitance and rate performance in the field of nickel cobalt sulfide electrode materials. In the paper, RuCoNiS electrodes were prepared using polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), xanthan gum (XG), and chitosan (CS) as binders. The surface wettability, morphological structure, specific surface area, and electrochemical performance of electrodes with different binders were analyzed by XRD, SEM, BET, CV, GCD, and EIS, etc. It's shown that the synthesis of CoNi2S is confirmed by XRD. The XPS results verify the existence of RuO2 and Ni2+/Ni3+ and Co2+/Co3+ redox couples. A cross-linked network structure is formed on the surface of the RuCoNiS by CS. The CS-RuCoNiS electrode has the largest specific surface area and microporosity. Ion migration in the electrolyte is facilitated by the excellent wettability of the CS-RuCoNiS electrode. The CS-RuCoNiS electrode reachs 1193.52 F g-1, which is 1.74 times higher than that of the PTFE-RuCoNiS electrode at 1 A g-1. The CS binder with its three-dimensional structure has the highest ionic conductivity of 2.29 × 10-4 S cm-1, a lower Rct, good cycling stability with a capacity retention of 84.3% after 5000 cycles at 200 mV s-1, and excellent rate performance of 85.6%. It can provide a practical application in supercapacitors.

Metabolic Checkpoints in Rheumatoid Arthritis

BackgroundRheumatoid Arthritis is a systemic autoimmune disease affecting 0.5-1% of the population. Despite a growing therapeutic armamentarium, RA remains incurable, and many patients suffer significant morbidity over time. The strongest genetic risk derives from HLA class II polymorphisms, implicating T cells as pathogenic drivers. Innate immune cells, e.g. monocytes and macrophages (Mⱷ) contribute to chronic tissue inflammation through an array of pro-inflammatory functions but also present antigen to autoreactive T cells. Differentiation, survival, and effector functions of both T cells and Mⱷ are ultimately controlled by their bioenergetic and biosynthetic programs, identifying cellular metabolism as a critical disease mechanism in RA. ObjectivesSummarize current knowledge about metabolic conditions in the RA joint and disease-relevant metabolic circuits shaping the effector repertoire of RA T cells and Mⱷ. ResultsThe rheumatoid joint is a glucose deplete tissue environment, selecting for invading immune cells that can survive on non-glucose fuel sources. Inflamed synovium instead offers the amino acid glutamine and RA CD4+ T cells and RA Mⱷ rely on glutamine and glutamate to support their pathogenic functions. The metabolic hallmark of RA T cells is their low mitochondrial performance, resulting in low ATP production, low generation of reactive oxygen species (ROS) and low availability of tricarboxylic acid (TCA) cycle intermediates, all shifting RA T cells towards autoreactivity. The underlying defect stems from insufficient repair of mitochondrial DNA (mtDNA). Functional consequences include reversal of the TCA cycle, accumulation of citrate and lack of malate production. Excessive citrate promotes cytoskeletal hyperacetylation, creating hypermigratory and tissue-invasive T cells. Surplus acetyl-CoA supports lipid droplet formation and lipotoxicity. Lack of malate production disrupts the malate-aspartate shuttle, restricts recovery of cytosolic NAD and drives the endoplasmic reticulum (ER) into expansion. The bioenergetically stressed ER accumulates TNF mRNA and turns RA T cells into TNF superproducers. ATP low production renders RA T cells susceptible to cell death, depositing highly inflammatory mtDNA in the tissue. Mitochondrial deficiency leads to a slowdown in glycolysis and pyruvate processing, such that RA CD4+ T cells shunt glucose towards the pentose phosphate pathway to support nucleotide synthesis and clonal proliferation. Metabolically deprived CD4+ T cells partner with Mⱷ that have highly functional mitochondria. A hallmark of RA Mⱷ is the high expression of the DNA binding protein RFX5, which co-ordinates adaptations to metabolic needs with function. RFX5 upregulates HLA-DR expression and induces the glutaminolytic enzyme glutamate dehydrogenase 1 (GLUD1), providing bioenergetic resources for antigen presentation and survival in the tissue. In essence, RA CD4+ T cells and Mⱷ function in a metabolically challenging environment and rewire their cellular metabolism to survive. Metabolic adaptations promote immunostimulation and tissue inflammation, triggering and sustaining rheumatoid synovitis.

Long Duration Forecasting and its Performance Capability for Seasonal Variation Modelling of Residual Chlorine Concentrations: A Comparative Evaluation of two Small-scale Water Distribution Systems in Japan

Chlorine dosing control is a critical task for health security, complying with drinking water quality standards while achieving customer satisfaction. In Japan, this became more difficult due to decreasing number of technical personnel as a result of declining population and huge retirement of veterans. As experienced-based dosing control still exists and is considered inefficient due to risks of inaccurate dosing and need of experienced manpower, streamlining of operations is needed. This study aims to address these concerns through the development and evaluation of a deep learning model for residual chlorine concentrations capable of forecasting long durations. In this paper, the model is investigated in seasonal timeframe analyzing trends and variations. Two water distributions systems of varying network—simple and complex, are also compared to further analyze model performance and versatility. The model utilizes the past 24 hours of flow rate, chlorine level at treatment plant, water temperature, and residual chlorine at private homes as input to predict the 12 hours ahead of residual chlorine at private homes evaluated at hourly training lengths of 0.5, 1, 1.5, 2 years. Results revealed that the model achieved high accuracy in predicting hourly residual chlorine with general increasing model error from winter, spring, autumn, and summer due to the progressing instabilities in chlorine concentrations from low to high temperatures. Moreover, smaller system tends to be more unstable incurring lower model performance relative to larger system. In terms of optimal training length, ≥1Y training models are found to have lesser chance of data drift occurrence prospectively reducing model retraining frequency in the future.

The impact of asset specificity on corporate tax avoidance: Do financial constraints and product market power matter?

Our findings reveal that asset specificity significantly enhances corporate tax avoidance, with firms exhibiting lower cash effective tax rates. Firms with higher asset specificity also engage in more aggressive tax avoidance strategies, including tax dodging and long-term tax planning. Additionally, our analysis indicates that the positive impact of asset specificity on tax avoidance is less pronounced in firms with lower ESG performance but is more pronounced in those facing negative demand shocks or operating during periods of economic policy uncertainty. We also find that financial constraints and product market power mediate the relationship between asset specificity and tax avoidance, with financial constraints serving as the dominant economic channel. These findings offer new insights into the factors driving corporate tax avoidance and highlight the complex interplay between asset specificity, financial constraints, product market power, and tax planning strategies.

Is Warm-Up Preservation Modulated by Biological Maturation and Sex? Effects on Lower Limbs Performance.

Children and adults may react differently to warm-up preservation due to different physical characteristics. This study aimed to: (i) assess the impact of different rewarm-up routines in swimmers during a transition phase (20-25 min), including passive rest (SWU) or dynamic activities (RWU), on countermovement jump and swimming start performances, and (ii) explore potential RWU adaptations considering maturity offset (peak height velocity-PHV) and sex. Performance was analyzed using mixed effect ANCOVA, considering protocol, maturity offset (pre-PHV, mid-PHV, post-PHV, and adv. post-PHV), and sex. Results favored RWU over SWU with substantial magnitudes for jump height: pre-PHV (min-20, ES = 1.21; min-25, ES = 1.65), mid-PHV (min-20, ES = 1.23; min-25, ES = 1.14), post-PHV (min-20, ES = 1.37; min-25, ES = 0.73), and adv. post-PHV (min-20, ES = 1.03; min-25, ES = 0.65). Significant interactions at 25 min (p = 0.033, 0.047) showed that RWU outperformed SWU, especially in younger groups (pre-PHV, mid-PHV). RWU was superior to SWU for the reactive strength index at 20 min (p = 0.042) and 25 min (p = 0.047), with females having lower RSI than males at 20 min (p = 0.008, p = 0.015) and 25 min (p = 0.049) in later developmental stages. The flight distance (p = 0.009) and horizontal hip velocity (p = 0.014) revealed significant three-way interactions, with the male adv. post-PHV group responding better to RWU. Knee angular velocity was also higher after RWU, with male adv. post-PHV group showing more pronounced improvements (p = 0.016). These results suggest that though RWU had higher influence in male adults, it is a valuable approach for varying ages athletes.

Mediation of beneficial effects of an alcohol-specific inhibition training on drinking of patients with alcohol use disorder: The role of cognitive demands and inhibitory performance

BackgroundA cognitively demanding, alcohol-specific inhibition training (Alc-IT) might enhance treatment success in patients with severe alcohol use disorder (AUD; Anonymus, 2023). An inhibitory working mechanism for Alc-IT has been discussed, but compelling evidence supporting this hypothesis is yet lacking. The present study investigates inhibitory performance during Alc-IT and examines whether inhibitory parameters mediate drinking outcome. MethodsPatients with AUD (N = 232) completed six sessions of either a standard or improved Alc-IT, differing in their inhibitory demands determined by Go/NoGo ratios in a modified Go-NoGo-task, or a control training. During these training sessions, data on inhibitory performance was collected. To assess differences in inhibitory performance and its improvement, alcohol-related errors of commission and relative performance, integrating accuracy and speed, were analyzed with hierarchical linear contrast models. Mediation analyses tested whether inhibitory performance predicted drinking outcome (percent days abstinent at 3-month follow-up). ResultsPatients in improved Alc-IT started with higher errors of commission (γ01(standard) = − 2.74, p < 0.001, R2 = 0.885) and a lower relative performance in the first training session compared to standard Alc-IT (γ01(standard) = 0.51, p = 0.004). They showed a steeper increase in relative performance until the final sixth session (γ1(s6),(standard) = -0.37, p = 0.024, R2 = 0.882). The effect of improved Alc-IT on drinking outcome was mediated by relative performance increase (bootstrap-CI [0.15, 7.11]). ConclusionHigher inhibitory demands enable larger improvements across sessions. Mediation analysis supports an inhibitory working mechanism. Tailoring inhibitory demands to individual performance capacity could optimize future Alc-IT.

The effect of scanning strategies on the defect distribution and mechanical properties of additive manufactured 316L stainless steel components

The effect of scanning strategies on defect distribution and mechanical properties of additive-manufactured (AM) 316L stainless steel components was investigated. Three scanning strategies (A1-stripe, A2-loop, A3-chessboard) were applied to study the defect characteristics using X-ray microscopy (XRM) and evaluate the resulting mechanical behavior through tensile tests. The results indicate that the chessboard strategy produces fewer, smaller, and more uniform defects, contributing to superior tensile strength and reduced anisotropy. In contrast, the loop strategy results in a higher density of elongated defects near the surface, leading to increased stress concentrations and lower tensile performance. This study provides insights into optimizing scanning strategies to enhance defect control, thereby improving the overall mechanical properties of 316L stainless steel in additive manufacturing. These findings are instrumental in advancing the process design for defect mitigation and structural integrity in AM components.

Sociodemographic predictors and cross-cultural comparisons in tests performance from the Cambridge Neuropsychological Testing Automated Battery (CANTAB) among children aged 6-8 years from Montevideo, Uruguay.

Cross-culturally comparative data on measures of executive function (EF) are essential, but the 6-8-year group remains insufficiently described. This study examined the sociodemographic predictors of EF test performance employing the Cambridge Neuropsychological Testing Automated Battery (CANTAB). It also compared developmental trends in EF among children from Uruguay, the United States, and Mexico. EFs were assessed with the Intra-dimensional/Extra-dimensional shift, Spatial Span (SSP), and Stockings of Cambridge (SOC) tests from the CANTAB. The study sample consisted of 6-8-year-old children from the Salud Ambiental Montevideo (SAM) cohort in Uruguay. Differences between cohorts were examined, and we performed generalized linear regressions to assess the association between sociodemographic factors, and each EF domain. The final sample consisted of 525 participants (mean age in months 82.5 ± 6.0). Across all ages, SAM children had significantly lower performance in the SSP and SOC tasks compared to U.S. and Mexican children. On the Intra-dimensional/Extra-dimensional shift task, SAM children had similar scores to U.S. and Mexican children. Mother's intelligence quotient (IQ; β = 0.01; 95% CI [0.005, 0.02]), child's IQ (0.02 [0.02, 0.03]), the HOME total score (0.02 [0.01, 0.03]), as well as HOME subscales of accompaniment (0.13 [0.07, 0.20]), enrichment (0.11 [0.06,0.16]), and physical environment (0.07 [0.03, 0.10]) were positively associated with the span length (SSP task). Child's IQ (0.02 [0.01,0.03]) was positively associated with the number of problems solved on the SOC test. Uruguayan children perform lower in working memory and planning tests than U.S. children but similarly to Mexican children, while cognitive flexibility is consistent across all groups. Further, mother and child IQ, as well as the home environment, are important predictors of EF. These differences should be examined in the context of diverse cultural values and sociodemographic factors affecting CANTAB construct validity in this population. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The Impact of Sleep Restriction on Cerebrovascular Reactivity and Cognitive Outcomes in Healthy Adolescents: A Pilot Crossover Trial

BackgroundThe underlying mechanism for the association between sleep restriction (SR) and unfavorable cognitive outcomes in children and adolescents remains unclear. This study aimed to understand the effect of 5-night experimental SR on magnetic resonance imaging (MRI) measurements of cerebrovascular reactivity (CVR) and cognitive function in adolescents. MethodsThis randomized crossover study compared two sleep conditions, SR and Control Sleep (CS) in a home setting. Healthy adolescents aged 15-18 years were recruited. The protocol began with two nights of baseline sleep to record participants’ habitual sleep duration, followed by the two sleep conditions in the randomly allocated sequence, either SR (6 hours in bed for 5 nights) followed by CS (9 hours in bed for 5 nights), or the reverse sequence. Their sleep-wake pattern was monitored by an accelerometer and a sleep diary throughout the study period. Cerebral hemodynamics were assessed by hypercapnic challenge blood oxygen level-dependent (BOLD) MRI of CVR. Cognitive function was evaluated by NIH Toolbox Cognitive Battery on the day immediately after each sleep condition. ResultsA total of 27 participants (8 males; mean age: 16.8 ± 0.7 years, range 15-18 years) were included in the study. The average sleep duration was significantly reduced in the SR condition compared to the CS condition (320±34 min vs. 426±45 min, p<0.001). The CVR in the temporal occipital fusiform cortex [adjusted β(95% CI)=−0.091(-0.010 to -0.172), p=0.032] and occipital lobe [adjusted β(95% CI)=−0.087 (−0.002 to −0.172), p=0.045] was significantly lower following the SR condition when compared to the CS condition. Participants also had lower performance scores in the inhibitory control [adjusted β(95% CI)=−6.0(−0.9 to −11.0), p=0.019] and cognitive flexibility [adjusted β(95% CI)=−6.6 (−1.7 to −11.6), p=0.008] domains after the SR condition when compared to the CS condition. ConclusionsShort-term SR is associated with poorer cognitive function possibly through reduced cerebral vasodilatory capacity in specific cognitive regions.

Performance analysis of a photovoltaic component integrated into a hybrid power plant in Southeast Mauritania

This study investigated the performance of photovoltaic components of the 1.3MW KIFFA hybrid power plant in Mauritania. Data from the plant's monitoring system (January-December 2021) was used to assess various performance metrics. The analysis revealed a high daily reference yield (5.60 h/d), indicating good solar resource availability. However, final and array yields (4.78 h/d and 4.86 h/d, respectively) suggested potential for improvement. System component efficiencies were within acceptable ranges, with particularly high inverter efficiency (98.31%). Array capture losses were moderate (0.74 h/d), and system losses were minimal (0.08 h/d). The annual performance ratio (86.33%) and capacity factor (19.91%) indicated good overall plant performance. These findings were then compared with data from similar installations in various climate zones to understand the impact of climatic variations on photovoltaic performance. Compared to installations in temperate zones with lower irradiation levels, the KIFFA plant's reference yield was significantly higher. However, the final and array yields were closer due to potentially higher operating temperatures in Mauritania affecting module efficiency. Interestingly, comparisons with installations in other desert regions with similarly high irradiation levels revealed lower performance, particularly in terms of final yield, (4.71 h/d) in Algéria (Adrar) and (4.10 h/d) in Oman (Muscat). This suggests that climatic factors beyond just sunlight availability, such as dust accumulation, may have played a significant role in their performance compared to the KIFFA plant.

Research on damage repair and high-velocity impact characteristics of thermoplastic composites

Low-velocity impact (LVI) can result in imperceptible damage to carbon fiber reinforced thermoplastic composites (CFRTP) laminates during service, leading to a reduction in structural strength. The thermal repair of damaged CFRTP laminates is conducted using the repairability of thermoplastic resin at high temperatures. However, the high-velocity impact characteristics of CFRTP laminates following thermal repair remain uncertain. This study examines CFRTP laminates made of two different materials (CF/PEEK and CF/PPS) with varying levels of low-velocity impact damage, and investigates the thermal repair process. A comparative experimental analysis examined the high-speed impact characteristics of CFRTP laminates under varying conditions. The results indicate that CF/PEEK laminates consistently exhibit superior compressive properties and impact resistance compared to CF/PPS laminates under similar conditions. Following damage from low-velocity impact, the compressive properties and high-velocity impact resistance of CFRTP laminates decrease, with CF/PPS laminates typically showing a lower performance retention rate. However, the thermal repair process proposed in this study significantly enhances the performance of CF/PPS laminates. Moreover, the degree of performance healing in CF/PPS laminates is consistently higher than that in CF/PEEK laminates, which is closely related to the semi-crystalline nature of PEEK resin.

보편적 학습설계와 증거기반교수를 적용한 수학 수업이 초등학생의 곱셈·나눗셈 성취도와 수학적 학습 태도에 미치는 효과

Objectives The purposes of this study was to examine the effects of mathematics instruction, incorporate Universal Design for Learning(UDL) and evidence-based instruction, on the multiplication and division achievement and mathematical learning attitudes of 4th grade elementary school students with typical or low achievement in mathematics. Methods The study involved 46 subjects, comprising students from two 4th-grade classes in a public elementary school in Seoul. The subjects were divided into experimental and control groups, with each group further subdivided based on their level of mathematics achievement. The experimental design employed a pretest-posttest control group design along with a repeated measures design. Improvements in students’ multiplication and division achievements were analyzed using a hierarchical linear growth model, while differences in attitudes towards mathematical learning were assessed using paired samples t-tests and analysis of covariance(ANCOVA). Results First, the rate of change in multiplication and division achievement among students with typical math performance in the experimental group was statistically significantly higher than that in the control group. Second, the rate of change in multiplication and division achievement among students with low math performance in the experimental group was significantly higher than that in the control group. Third, within the experimental group, students with low math performance demonstrated a significantly greater rate of improvement in achievement compared to students with typical math performance. Fourth, students in the experimental group showed statistically significant improvement in most areas of mathematical learning attitudes. Finally, there was no statistically significant difference in mathematical learning attitudes between the two subgroups of the experimental group, except for their level of confidence in multiplication and division. Conclusions First, mathematics instruction incorporating Universal Design for Learning (UDL) and evidencebased instruction was effective in improving multiplication and division achievement as well as mathematical learning attitudes among 4th grade elementary students. Finally, it can be inferred that this approach could be an effective method for ensuring foundational academic skills and bridging achievement gaps in general education settings with diverse student characteristics.

주식시장 수익률과 개인 투자자의 매매 성향

This study examines the relationship between individual investors and the KOSPI stock market using long-term data spanning 25 years from 1999 to 2023. However, this study analyzes the relationship between individual investors' net buys and KOSPI returns by dividing the entire period into five sun-periods of five years and applying two-sided regression and structural vector autoregressive (SVAR) models. The main findings are as follows: First, compared to foreign investors, both institutional and individual investors exhibit relatively higher turnover ratios. Second, cross-sectional analysis shows that KOSPI returns decrease monotonically with the individuals' net buys. Third, the results of the two-sided regressions indicate a Granger causality, where past returns negatively influence individual investors' net buys. In addition, today's individual net buys negatively Granger cause future returns. Fourth, the SVAR analysis also shows that KOSPI returns have a strong negative effect on individual net buys. Finally, according to the results of SVAR impulse response function, net buys response negatively to KOSPI shocks, and this response dissipates almost entirely by the third day. In summary, individual investors tend to engage in net selling in response to positive news in the KOSPI market, and this tendency may be a key reason for their lower performance.