STUDY OF DROPLETS INTERACTIONS ON SOLID SURFACE FOR MANUFACTURING APPLICATIONS

Droplet impact behaviors on a solid substrate is a complicated process that involves multiple phenomena on a small scale within a short time. This phenomenon has wide applications in the industrial, medical, and scientific fields. To understand the complicated mechanism, we select the oscillation process as the marked phase to observe and analyze the dynamical balancing between different forces and conservation of energies and compare it to the typical damped harmonic oscillator (DHO) model to examine the character of variables as viscosity, surface tension, and wettability. From the testing results, we created a precise model for post-impact dynamics and described how the solid wettability (which is demonstrated as the contact angle) and the surface tension (which is presented as the weber number) helped control the oscillation dynamics; then further studies reveal the influence of weber number on oscillation frequencies and make a capillary pressure related assumption about satellite droplet separated from the main body. Finally, the latest study reveals the viscosities’ influence on the dynamics. By creating the overall functions of the Weber and Reynolds numbers, we created a model that can represent the oscillation process under a wide range of conditions

Chinese Fertility: Past, Present And Future

China has witnessed profound socioeconomic changes over the past four decades. This dissertation is comprised of three papers that investigate the demographic, social, and economic determinants of fertility trends in China. In Chapter 1, I discuss how birth control policies, which have been implemented since 1980, are related to Chinese women’s timing of giving first birth during a period with substantial socioeconomic development. The results suggest that such birth control policies still influence women’s childbearing behavior, even after controlling for the urban/rural distinction and provincial variation; however, this influence has diminished over time. In Chapter 2, I examine the relationship between different motherhood stages and urban women’s economic positions in the labor market between 1991 and 2011, and how this relationship has changed with the development of local economies. The analysis shows that very young children have an inhibiting effect on mothers’ labor force activities, and this effect is exaggerated with the development of local economies. On the other hand, women’s income is positively correlated with the presence of school-aged children, but this positive relationship is eroded with local economic development. In Chapter 3, I propose that the legacies from state socialism, the reduction in educational gender inequality, and the marketization process lead to a modern-traditional mosaic that shapes a curvilinear relationship between gender-role ideology and fertility intentions in China. Capitalizing on three waves of data from the Chinese General Social Survey, I empirically explore the relationship between women’s fertility intentions of having two or more children and different gender-role attitudes by using structural equation modeling. The results suggest that both the ‘modern’ (with more egalitarian gender-role ideology) and ‘traditional’ (with less egalitarian gender-role ideology) women show higher fertility intentions

Effects of Birth Control Policies on Women’s Age at First Birth in China

The end of the “one-child” policy in China has brought the discussion of how much birth control policies have actually affected women’s childbearing behavior back into the spotlight. Some people suggest that birth control policies explain most of the fertility decline in China, but others believe that socioeconomic development has also played a decisive role. To shed light on these questions, instead of analyzing the impacts of policies on the overall level of fertility directly, we explore the effects of different local birth control policies on another aspect of childbearing behavior, timing of first birth. This study yields two significant findings. First, women who followed less strict birth control policies tended to have their first birth earlier than those who followed the strictest one-child policy. Second, concurrent with educational expansion, there was more heterogeneity in fertility intentions and variation in birth control policies among younger, higher-educated cohorts than their older, less-educated counterparts. Together, these imply that the effect of birth control policies was still strong, even for more educated young women. The Chinese fertility rate might see a temporal rise under the newly loosened birth control policy while the trend to low fertility will continue in the medium to long term

The Effect of Virtual Team Characteristics in Co-creation on the Quality of UGC Videos

Co-creation is a newly emerging video production method on the UGC video platform. Based on the transactive memory systems and social capital theory, this paper describes the characteristics of the virtual team formed in the co-creation, and further explores the influence of virtual team characteristics and member characteristics on video quality. This paper collects 49,785 Bilibili co-creation video data, and uses natural language processing methods and quantitative analysis methods to carry out empirical research. The study found that the specialization of virtual teams has an inverted U-shaped impact on video quality, while coordination has a positive impact and credibility has a negative impact. Additionally, the trendiness and fame of team members can enhance the inverted U-shaped impact of specialization, and fame also enhance the impact of coordination. The research results provide theoretical support for creators and managers to optimize the co-creation mode on UGC platforms

Dynamical properties of quantum many-body systems with long range interactions

Employing large-scale quantum Monte Carlo simulations, we systematically compute the energy spectra of the 2D spin-1/2 Heisenberg model with long-range interactions. With the $1/r^{\alpha}$ ferromagnetic and staggered antiferromagnetic interactions, we find the explicit range in $\alpha$ for {\color{black} the short-range Goldstone-type (gapless), anomalous Goldstone-type (gapless) and Higgs-type (gapped) spectra. Accompanied by the spin wave analysis, our numerical results vividly reveal how the long-range interactions alter the usual linear and quadratic magnon dispersions in 2D quantum magnets and give rise to anomalous dynamical exponents. Moreover, we find explicit case where the gapped excitation exists even when the Hamiltonian is extensive. This work provides the first set of unbiased dynamical data} of long-range quantum many-body systems and suggests that many universally accepted low-energy customs for short-range systems need to be substantially modified for long-range ones which are of immediate relevance to the ongoing experimental efforts from quantum simulators to 2D quantum moir\'e materials.Comment: 5 pages,3 figure

Member stability of stainless steel welded I-section beam-columns

A comprehensive experimental and numerical study is presented into the behaviour of stainless steel welded I-section beams-columns. Twenty test specimens were fabricated from grade 304 (EN 1.4301) austenitic and grade 2205 (EN 1.4406) duplex stainless steel plates – ten were tested under major axis bending plus compression and ten under minor axis bending plus compression. Material tensile coupon tests and geometric imperfection measurements were also conducted. Numerical models were developed, calibrated against the test results and subsequently employed in parametric studies considering a wider range of specimen geometries. Based on the obtained test and numerical results, the accuracy and reliability of existing design rules given in EN 1993-1-4 and AISC DG 27, as well as recent proposals, were assessed

Finite-temperature critical behaviors in 2D long-range quantum Heisenberg model

The well-known Mermin-Wagner theorem prohibits the existence of finite-temperature spontaneous continuous symmetry breaking phase in systems with short-range interactions at spatial dimension $D\le 2$ [Phys. Rev. 158, 383; Phys. Rev. Lett. 17, 1133; Journal of Statistical Physics 175, 521-529]. For long-range interaction with monotonic power-law form ($1/r^{\alpha}$), the theorem further forbids a ferro- or antiferromagnetic order at finite temperature when $\alpha\ge 2D$[Phys. Rev. Lett. 87, 137203]. However, the situation for $\alpha \in (2,4)$ at $D=2$ is beyond the predicting power of the theorem and the situation is still unclear. Here we address this question by large-scale quantum Monte Carlo simulations, accompanied with field theoretical analysis. We find the spontaneous breaking of the $SU(2)$ symmetry for $\alpha \in (2,4)$ in ferromagnetic Heisenberg model with $1/r^{\alpha}$ interaction at $D=2$, and obtain the accurate critical exponents by finite-size analysis for $\alpha<3$ where the system is above the upper critical dimension with Gaussian fixed point and for $3\le\alpha<4$ where the system is below the upper critical dimension with non-Gaussian fixed point. Our results reveal the novel critical behaviors in 2D long-range Heisenberg models and will intrigue further experimental studies of quantum materials with long-range interaction beyond the realm of the Mermin-Wagner theorem

Quantum criticality and entanglement for 2d long-range Heisenberg bilayer

The study of quantum criticality and entanglement in systems with long-range (LR) interactions is still in its early stages, with many open questions remaining. In this work, we investigate critical exponents and scaling of entanglement entropies (EE) in the LR bilayer Heisenberg model using large-scale quantum Monte Carlo (QMC) simulations and the recently developed nonequilibrium increment algorithm for measuring EE. By applying modified (standard) finite-size scaling (FSS) above (below) the upper critical dimension and field theory analysis, we obtain precise critical exponents in three regimes: the LR Gaussian regime with a Gaussian fixed point, the short-range (SR) regime with Wilson-Fisher (WF) exponents, and a LR non-Gaussian regime where the critical exponents vary continuously from LR Gaussian to SR values. We compute the R\'enyi EE both along the critical line and in the N\'eel phase and observe that as the LR interaction is enhanced, the area-law contribution in EE gradually vanishes both at quantum critical points (QCPs) and in the N\'eel phase. The log-correction in EE arising from sharp corners at the QCPs also decays to zero as LR interaction grows, whereas the log-correction for N\'eel states, caused by the interplay of Goldstone modes and restoration of the symmetry in a finite system, is enhanced as LR interaction becomes stronger. We also discuss relevant experimental settings to detect these nontrivial properties in critical behavior and entanglement information for quantum many-body systems with LR interactions.Comment: 5pages, 4 figure

MP2: A Momentum Contrast Approach for Recommendation with Pointwise and Pairwise Learning

Binary pointwise labels (aka implicit feedback) are heavily leveraged by deep learning based recommendation algorithms nowadays. In this paper we discuss the limited expressiveness of these labels may fail to accommodate varying degrees of user preference, and thus lead to conflicts during model training, which we call annotation bias. To solve this issue, we find the soft-labeling property of pairwise labels could be utilized to alleviate the bias of pointwise labels. To this end, we propose a momentum contrast framework (MP2) that combines pointwise and pairwise learning for recommendation. MP2 has a three-tower network structure: one user network and two item networks. The two item networks are used for computing pointwise and pairwise loss respectively. To alleviate the influence of the annotation bias, we perform a momentum update to ensure a consistent item representation. Extensive experiments on real-world datasets demonstrate the superiority of our method against state-of-the-art recommendation algorithms.Comment: This paper was accepted at SIGIR 202