Heat Exchanger Design with Topology Optimization

Topology optimization is proving to be a valuable design tool for physical systems, especially for structural systems. However, its application in the field of heat transfer is less evident but is constantly progressing. In this chapter, we would like to introduce topology optimization in the context of heat exchanger design to the general reader. We also provide a chronological review of available literature to see the current progress of topology optimization in the field of heat transfer and heat exchanger design. We expect that topology optimization will prove to be a valuable tool in heat exchanger design for the coming years

Set voltage distribution stabilized by constructing an oxygen reservoir in resistive random access memory

In this letter, the instability mechanism of RRAM was investigated, and a technique was developed to stabilize the distribution of high resistance state (HRS) and better concentrate the SET voltage. In previous research, we found that an interface-type switching characteristic was observed on the I-V curve beneath the filament-type switching behavior, owing to the oxygen accumulation effect. In this letter, this interface-type switching characteristic is used to fit the natural distribution of HRS for an analysis of the instability mechanism. According to the results, the reason for the HRS distribution is the accumulation of extra oxygen ions which are left over from a lower degree of oxygen and oxygen vacancy recombination during the reset process. We propose a solution which creates an extra oxygen reservoir by changing the surface topography of the electrode to store the surplus oxygen ions from the reset process, eliminating the accumulation effect, and indeed improving stability. Please click Additional Files below to see the full abstract

{μ-6,6′-Dimeth­oxy-2,2′-[ethane-1,2-diyl­bis(nitrilo­methanylyl­idene)]diphenolato-1κ4 O 6,O 1,O 1′,O 6′;2κ4 O 1,N,N′,O 1′}(methanol-1κO)(tetra­fluoridoborato-1κ2 F,F′)-2-copper(II)-1-sodium

In the dinuclear salen-type title complex, [CuNa(BF4)(C18H18N2O4)(CH3OH)], the CuII atom is chelated by two O atoms and two N atoms of the deprotonated Schiff base in a square-planar geometry. The Na atom is seven-coordinate as it is linked to four O atoms of the same Schiff base ligand, one O atom of the methanol and two tetra­fluorido­borate F atoms. The remaining two F atoms of the anion are disordered over two sites in a 0.598 (18):0.402 (18) ratio

INVESTIGATING THE INFLUENCE OF AUTHORITARIAN LEADERSHIP AND SUPERVISOR SATISFACTION ON TURNOVER INTENTION: THE MODERATING ROLE OF EMPLOYEE UPBRINGING

Authoritarian leadership is prevalent in the Asian region, and previous research has found a positive correlation between authoritarian leadership and employees' intention to leave their jobs. However, there are employees in the workplace who can adapt to such supervisors. Therefore, we approach this study from the perspective of "fit theory" to explore whether employees with authoritarian family upbringing can match with authoritarian leadership. This study aims to investigate the impact of authoritarian leadership on employees' intention to leave, with supervisor satisfaction as the mediator and employees' authoritarian family upbringing as the moderator. A total of 232 valid questionnaires were collected in this study. The results revealed that the level of authoritarian family upbringing among employees has a moderating effect on the relationship between authoritarian leadership and supervisor satisfaction

The risk factors of progestational anxiety, depression, and sleep disturbance in women with recurrent pregnancy loss: A cross-sectional study in China

BackgroundThe risk factors of progestational anxiety, depression, and sleep disturbance in women with a history of recurrent pregnancy loss (RPL) remain controversial, additional study is needed to investigate the incidence and risk factors of progestational anxiety, depression, and sleep quality in RPL women.MethodsA cross-sectional study was conducted among 663 non-pregnant RPL women in Northeast China from October 2019 to July 2022. We assessed the state of anxiety, depression, and sleep quality before pregnancy using structured questionnaires, including sociodemographic characteristics, state-trait anxiety scale (STAI), center for epidemiological survey, depression scale (CES-D), Pittsburgh sleep quality index (PSQI), and symptom self-rating scale (SCL-90). Logistic regression was used to evaluate the association between sleep quality and anxiety, depression. Pearson’s correlation was used to evaluate the correlation between anxiety and depression. Multivariate logistic regression analysis was used to find the risk factors of depression symptoms. The receiver operating characteristic curve (ROC) was used to evaluate the predictive value of the model.ResultsThe incidence of state anxiety, trait anxiety, depression, and sleep disturbance in RPL women were 60.3, 51.7, 33.9, and 31.2%, respectively. The level of anxiety and depression in RPL women varied at different stages of treatment. In a longitudinal study (25 pairs), we found the level of state anxiety and trait anxiety were significantly lower after the cause was identified. Sleep disturbance is positively correlated with anxiety and depression. Logistic regression showed that the number of miscarriages ≥4 (Odds ratio (OR) = 2.268, 95%CI 1.300–3.956), Low household family income (OR = 1.613, 95%CI 1.036–2.513/OR = 2.361, 95%CI 1.095–5.092), interval since last miscarriage <6 months (OR = 2.154, 95%CI 1.246–3.726) and sleep disturbance (OR = 5.523, 95%CI 3.542–8.614) were associated with the occurrence of depressive symptoms. At the same time, anxiety can be used as a predictor of depression.ConclusionRecurrent pregnancy loss women have a certain degree of anxiety, depression, and sleep disturbance. Education level, interval since the last miscarriage <6 months, and sleep disturbance are risk factors for anxiety and depression. A history of pregnancy loss after 14 weeks and no living birth are also closely related to anxiety. Therefore, it is necessary to pay close attention to the psychological state of RPL women and provide appropriate psychosocial support to reduce the occurrence of negative emotions

Spatially resolved MaNGA observations of the host galaxy of superluminous supernova 2017egm

Superluminous supernovae (SLSNe) are found predominantly in dwarf galaxies, indicating that their progenitors have a low metallicity. However, the most nearby SLSN to date, SN 2017egm, occurred in the spiral galaxy NGC 3191, which has a relatively high stellar mass and correspondingly high metallicity. In this paper, we present detailed analysis of the nearby environment of SN 2017egm using MaNGA IFU data, which provides spectral data on kiloparsec scales. From the velocity map we find no evidence that SN 2017egm occurred within some intervening satellite galaxy, and at the SN position most metallicity diagnostics yield a solar and above solar metallicity (12 + log (O/H) = 8.8-9.1). Additionally we measure a small H-alpha equivalent width (EW) at the SN position of just 34 Angs, which is one of the lowest EWs measured at any SLSN or Gamma-Ray Burst position, and indicative of the progenitor star being comparatively old. We also compare the observed properties of NGC 3191 with other SLSN host galaxies. The solar-metallicity environment at the position of SN 2017egm presents a challenge to our theoretical understanding, and our spatially resolved spectral analysis provides further constraints on the progenitors of SLSNe.Comment: Accepted version in ApJ Letter. Thank you for useful comment