Finite-element modeling of liquid-crystal hydrodynamics with a variable degree of order

A finite-element model of liquid-crystal hydrodynamics based on the Qian and Sheng formulation has been developed. This formulation is a generalization of the Ericksen-Leslie theory to include variations in the order parameter, allowing for a proper description of disclinations. The present implementation is well suited to treat properly the various length scales necessary to model large regions yet resolve the rapid variations in the order parameter in proximity to disclinations

Modeling of weak anisotropic anchoring of nematic liquid crystals in the Landau-de Gennes theory

The anisotropic anchoring effect of a treated solid surface on a nematic liquid crystal is described in the Landau-de Gennes theory using a power expansion on the tensor-order parameter and two mutually orthogonal unit vectors. The expression has three degrees of freedom, allowing for independent assignment of polar and azimuthal anchoring strengths and a preferred value of the surface-order parameter. It is shown that in the limit for a uniaxial constant-order parameter, the expression simplifies to the anisotropic generalization of the Rapini-Papoular anchoring energy density proposed by Zhao et al. Experimentally measurable values with a physical meaning in the Oseen-Frank theory can be scaled and assigned to the scalar coefficients of the tensor-order-parameter expansion. Results of numerical experiments comparing the anchoring according to the study of Zhao et al. in the Oseen-Frank theory and the power expansion in the Landau-de Gennes theory are presented and shown to agree well

post-Adaptation vulnerability of cereals to rainfall and temperature variability in the federal capital territory of Nigeria

This study assessed the vulnerability of cereals yield to climate change using an integrated and multi-scale quantitative approach. The objectives of this study include determining the level of climate variability, assessment of cereals yield sensitivity index, determining climate exposure index, determining adaptive capacity of farmers, assessment of the post adaptation vulnerability of cereals yield to climate change. Socioeconomic data were obtained through administration of questionnaires. Thirty years data of temperature and rainfall as well as fifteen years data of annual cereals yield were used. Mean and standard deviation, standardized coefficient of skewness (Z1) and kurtosis (Z2), simple linear regression and time series statistics analysis were used in this study for the analysis of data. Finding depicts that the exposure index of rainfall is low but high for temperature. Cereals sensitivity index/degree of crop yield failure is more from 2000 – 2010 and significant difference was observed in sensitivity index for all the cereals. Adaptive capacity of farmers to climate change is high in Bwari and AMAC but low in Gwagwalada, Kuje, Abaji and Kwali. Post adaptation vulnerability of maize, rice and millet yield to rainfall and temperature is low in AMAC and Bwari but high in Gwagwalada, Kwali, Abaji and Kuje. Post adaptation vulnerability of sorghum in relation to rainfall is low in all the area councils in the FCT except Abaji. In relation to temperature, vulnerability of sorghum is high in Abaji and Kuje but low in AMAC, Gwagwalada, Kwali and Bwari. It was recommended that there is need to place climate change within the top priority of developmental context, and provision and infrastructure as well as reliable agricultural extension service.  Key Words: Cereals, Post-Adaptation, Vulnerability, Rainfall, Temperature, Variability, FC

Globalization, Trade & Wages: What Does History tell us about China?

Chinese imports and exports grew rapidly during the first three decades of the twentieth century as China opened up to global trade. Using a new data set on the factor-intensity of traded goods at the industry level, we show that Chinese exports became more unskilled-intensive and imports became more skill-intensive during these three decades. The exogenous shock of World War I dramatically raised the price of Chinese exports and increased the demand for these goods overseas and for unskilled workers producing these goods in China. When the war ended, trade costs declined, leading to a rise in China’s terms of trade and further growth in China’s export sector. Difference-in-differences regression estimates show that World War I boosted exports in China and did so substantially more for unskilled industries than skilled industries. We show that the observed decline in the skill premium in China is consistent with China’s changing terms of trade. The skill-unskilled wage ratio flattened out during the 1910s and then fell by eight percent during the 1920s. We simulate the effects of World War I using a dynamic, general equilibrium factor-endowments model of trade, and demonstrate that an exogenous shock to the price of traded goods can produce a decline in the skill premium similar to what China experienced in the 1920s.

Understanding Continued IT Usage: An Extension to the Expectation-Confirmation Model in IT Domain

A model that has been proposed to investigate the continued IT usage behavior is the Expectation-Confirmation Model in IT Domain (ECM-IT). This paper proposes an extension to the ECM-IT that incorporates perceived ease of use; provide empirical evidence for the utility of the extended ECM-IT; and deepen our knowledge about the factors affecting the continued IT usage behavior. The extended ECM-IT was tested with data collected from 1,826 Mobile Data Services (MDS) users. The LISREL analysis showed that the extended ECM-IT has good explanatory power (R(2) =67%), with perceived ease of use having a stronger impact on user satisfaction and continued usage intention than perceived usefulness. Hence, the extended ECM-IT can provide valuable additional information that is relevant for understanding continued IT usage. The strong impact of perceived ease of use on user satisfaction and intention implies that the nature of the target technology can he an important boundary condition in understanding the continued IT usage behavior. At a more specific level, the extended ECM-IT provides practitioners with deeper insights into how to address customer satisfaction and retention

Angle-dependence of quantum oscillations in YBa2Cu3O6.59 shows free spin behaviour of quasiparticles

Measurements of quantum oscillations in the cuprate superconductors afford a new opportunity to assess the extent to which the electronic properties of these materials yield to a description rooted in Fermi liquid theory. However, such an analysis is hampered by the small number of oscillatory periods observed. Here we employ a genetic algorithm to globally model the field, angular, and temperature dependence of the quantum oscillations observed in the resistivity of YBa2Cu3O6.59. This approach successfully fits an entire data set to a Fermi surface comprised of two small, quasi-2-dimensional cylinders. A key feature of the data is the first identification of the effect of Zeeman splitting, which separates spin-up and spin-down contributions, indicating that the quasiparticles in the cuprates behave as nearly free spins, constraining the source of the Fermi surface reconstruction to something other than a conventional spin density wave with moments parallel to the CuO2 planes.Comment: 8 pages, 4 figure

DeTorrent: An Adversarial Padding-only Traffic Analysis Defense

While anonymity networks like Tor aim to protect the privacy of their users, they are vulnerable to traffic analysis attacks such as Website Fingerprinting (WF) and Flow Correlation (FC). Recent implementations of WF and FC attacks, such as Tik-Tok and DeepCoFFEA, have shown that the attacks can be effectively carried out, threatening user privacy. Consequently, there is a need for effective traffic analysis defense. There are a variety of existing defenses, but most are either ineffective, incur high latency and bandwidth overhead, or require additional infrastructure. As a result, we aim to design a traffic analysis defense that is efficient and highly resistant to both WF and FC attacks. We propose DeTorrent, which uses competing neural networks to generate and evaluate traffic analysis defenses that insert 'dummy' traffic into real traffic flows. DeTorrent operates with moderate overhead and without delaying traffic. In a closed-world WF setting, it reduces an attacker's accuracy by 61.5%, a reduction 10.5% better than the next-best padding-only defense. Against the state-of-the-art FC attacker, DeTorrent reduces the true positive rate for a $10^{-5}$ false positive rate to about .12, which is less than half that of the next-best defense. We also demonstrate DeTorrent's practicality by deploying it alongside the Tor network and find that it maintains its performance when applied to live traffic.Comment: Accepted to the 24th Privacy Enhancing Technologies Symposium (PETS 2024

Prevalence of Illicit Use and Abuse of Prescription Stimulants, Alcohol, and Other Drugs Among College Students: Relationship with Age at Initiation of Prescription Stimulants

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90112/1/phco.27.5.666.pd