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Understanding Precedents for Frontline Employee Turnover in Luxury Hotels: Emotional Intelligence as a Unifying Factor
No full textDr. Chenchen Huang is an Associate Professor with the Hospitality and Tourism Department at Buffalo State-State University of New York.
Dr. Kai Wu is a Lecturer with the School of Tourism and Hotel Management at Dongbei University of Finance and Economics.Passport to Research (Visual Papers
Sensitivity of endemic behaviour of COVID-19 under a multi-dose vaccination regime, to various biological parameters and control variables
No full textFor an infectious disease such as COVID-19, we present a new four-stage vaccination model (unvaccinated, dose 1 + 2, booster, repeated boosters), which examines the impact of vaccination coverage, vaccination rate, generation interval, control reproduction number, vaccine efficacies and rates of waning immunity upon the dynamics of infection. We derive a single equation that allows computation of equilibrium prevalence and incidence of infection, given knowledge about these parameters and variable values. Based upon a 20-compartment model, we develop a numerical simulation of the associated differential equations. The model is not a forecasting or even predictive one, given the uncertainty about several biological parameter values. Rather, it is intended to aid a qualitative understanding of how equilibrium levels of infection may be impacted upon, by the parameters of the system. We examine one-at-a-time sensitivity analysis around a base case scenario. The key finding which should be of interest to policymakers is that while factors such as improved vaccine efficacy, increased vaccination rates, lower waning rates and more stringent non-pharmaceutical interventions might be thought to improve equilibrium levels of infection, this might only be done to good effect if vaccination coverage on a recurrent basis is sufficiently high
Symplocodes marmorata subsp. marmorata marmorata (Brunner von Wattenwyl 1893
No full textSymplocodes marmorata marmorata (Brunner von Wattenwyl, 1893) (Figures 1C, D, 3A – L, 8G – I) Phyllodromia marmorata Brunner von Wattenwyl, 1893: 19. Hemithyrsocera marmorata: Shelford, 1912: 661. Symplocodes marmorata: Princis, 1971: 1130; Roth, 1999: 137. Phyllodromia feae Shelford, 1908: 13. Symplocodes feae: Princis, 1971: 1130. Materials examined Two males, China, Xizang Aut. Reg., Motuo, 1050 m, 1 August 1979, coll. GT Jin and JY Wu; one male, China, Yunnan Prov., Yingjiang, Nabang, 282 m, 11 July 2012, coll. D Wang; one male, China, Xizang Aut. Reg., Motuo, 9 July 2013, coll. KL Wu. (SWU) Distribution China (Yunnan, Xizang); Myanmar, Thailand.Published as part of Zheng, Yuhong, Wang, Chenchen, Che, Yanli & Wang, Zongqing, 2015, The species of Symplocodes Hebard (Blattodea: Ectobiidae: Blattellinae) with description of a new species from China, pp. 339-361 in Journal of Natural History 50 on page 345, DOI: 10.1080/00222933.2015.1079337, http://zenodo.org/record/399208
Research on segmented mirror position error of optical system based on ZEMAX
No full text
We have modeled a segmented mirror optical system by software ZEMAX, and analyzed influence of segmented mirror's position error to the optical system imaging for the first time to author's best knowledge. The primary mirror is composed of 18 segmented mirrors. By adjusting each one's position error of six freedoms, we get six relationship curves between position error and the optical system's image quality. The relationship curves show that some have different wave-front error RMS values when segmented mirrors have same position errors. The middle mirrors are sensitive to the movement along X axis direction, and the outer ones are sensitive to the movement along Y axis direction. The middle ones and outer ones are all sensitive to the tilt error, especially tilt along X, Y axis. (C) 2017 Elsevier GmbH. All rights reserved.</p
The complexity of finding and enumerating optimal subgraphs to represent spatial correlation
No full textUnderstanding spatial correlation is vital in many fields including
epidemiology and social science. Lee, Meeks and Pettersson (Stat. Comput. 2021)
recently demonstrated that improved inference for areal unit count data can be
achieved by carrying out modifications to a graph representing spatial
correlations; specifically, they delete edges of the planar graph derived from
border-sharing between geographic regions in order to maximise a specific
objective function. In this paper we address the computational complexity of
the associated graph optimisation problem. We demonstrate that this problem
cannot be solved in polynomial time unless P = NP; we further show
intractability for two simpler variants of the problem. We follow these results
with two parameterised algorithms that exactly solve the problem. Both of these
solve not only the decision problem, but also enumerate all solutions with
polynomial time precalculation, delay, and postcalculation time in respective
restricted settings. For this problem, efficient enumeration allows the
uncertainty in the spatial correlation to be utilised in the modelling. The
first enumeration algorithm utilises dynamic programming on a tree
decomposition, and has polynomial time precalculation and linear delay if both
the treewidth and maximum degree are bounded. The second algorithm is
restricted to problem instances with maximum degree three, as may arise from
triangulations of planar surfaces, but can output all solutions with FPT
precalculation time and linear delay when the maximum number of edges that can
be removed is taken as the parameter.Comment: Added a number of enumeration result
Radiographic features and subtypes of congenital thumb duplication type C3 according to Wu et al. and their potential implications for surgical management: new classification and preliminary results
No full textAbstract Background Wu et al. introduced a modified radiographic system that allows classification of all forms of CTD with excellent interobserver and intraobserver reliability. No study to date has evaluated the radiographic characteristics of Wu et al. type C3 CTD with osseous attachment at the level of the metacarpal. Objective This study aimed to evaluate the radiographic features of type C3 CTD according to the system of Wu et al., to describe the different anatomical subtypes of the duplication, and to propose a categorization approach to distinguish diverse surgical strategies based on the radiographic anatomy of this specific subtype of duplication. Methods We performed a retrospective analysis of 215 patients (221 thumbs) diagnosed with Wu et al. type C3 CTD at our Institution between 2015 and 2021. We evaluated all CTDs by examining the alignment of the interphalangeal (IP) and metacarpophalangeal (MP) joints and by assessing the presence of abnormal hypertrophic epiphysis of the primary thumb on posteroanterior (PA) radiographs. The proposed classification system has four types: Type I with good alignment of both MP and IP joints, Type II with ulnar deviation of the MP joint, Type III with radial deviation in the MP joint and Type IV with abnormal hypertrophic epiphysis of the distal phalanx of the main thumb with ulnar deviation of the IP joint with or without ulnar deviation of the MP joint. Results There were 140 male and 75 female patients with CTD (221 thumbs). There were 65 left, 144 right and 6 bilateral forms. The right-to-left, male-to-female and unilateral-to-bilateral ratios were 2.2:1, 1.9:1 and 35.8:1 respectively. The mean age at surgery was 22.3 ± 11.8 months (range, 8–80). The proposed classification system allowed the classification of all CTDs (n = 221). Specifically, 53 fingers were classified as Type I (24%), 136 as Type II (61.5%), 21 as Type III (9.5%), and 11 as Type IV (5%). Conclusion The proposed system is based on radiographic pathoanatomy and complements that of Wu et al. by identifying four distinct subtypes of deformity. It has the potential to improve inter-professional communication and guide surgery in patients with Wu et al. type C3 CTD. However, our results are preliminary and further research is needed to validate them. Level of evidence III
Statistical Learning for Latent Attribute Models
No full textLatent variable models are popularly used in unsupervised learning to uncover the latent structures underlying observed data and have seen great successes in representation learning in many applications and scientific disciplines. Latent attribute models, also known as cognitive diagnosis models or diagnostic classification models, are a special family of discrete latent variable models that have been widely applied in modern psychological and biomedical research with diagnostic purposes. Despite the wide usage in various fields, the models' discrete nature and complex restricted structures pose many new challenges for efficient learning and statistical inference. Moreover, with the large-scale item and subject pools emerging in modern educational and psychological measurements, efficient algorithms for uncovering latent structures of both items and subjects are desired. This dissertation studies four important problems that arise in this context.
(I) The first part develops novel methodologies and efficient algorithms to learn the latent and hierarchical structures in latent attribute models. Specifically, researchers in many applications are interested in hierarchical structures among the latent attributes, such as prerequisite relationships among target skills in educational settings. However, in most cognitive diagnosis applications, the number of latent attributes, the attribute-attribute hierarchical structures, the item-attribute dependence structures, as well as the item-level diagnostic models, need to be fully or partially pre-specified, which may be subjective and misspecified as noted by many recent studies. In this part, we consider the problem of jointly learning these latent quantities and hierarchical structures from observed data with minimal model assumptions. A penalized likelihood approach is proposed for joint learning, an Expectation-Maximization (EM) algorithm is developed for efficient computation, and statistical consistency theory is established under mild conditions.
(II) The second part generalizes the methodologies in part I to simultaneously infer the subgroup structures of both subjects and items. We consider the model-based co-clustering algorithms and aim to automatically select numbers of clusters and uncover latent block structures. Specifically, based on latent block models, we propose a penalized co-clustering approach that is capable of learning the numbers of clusters and inner block structures simultaneously. Efficient EM algorithms have been developed and comprehensive simulation studies demonstrate their superiority.
(III) The third part concerns the important yet unaddressed problem of testing the latent hierarchical structures in latent attribute models. Testing the hierarchical structures is shown to be equivalent to testing the sparsity structure of the proportion parameter vector. However, due to the irregularity of the problem, the asymptotic distribution of the popular likelihood ratio test becomes nonstandard and tends to provide unsatisfactory finite sample performance under practical conditions. To tackle these challenges, we discuss the conditions of testability issues, provide statistical understandings of the failures, and propose a practical resampling-based procedure.
(IV) The fourth part introduces a unified estimation framework to bridge the gap between parametric and nonparametric methods in cognitive diagnosis to better understand their relationship. In particular, a number of parametric and nonparametric methods for estimating latent attribute models have been developed and applied in a wide range of contexts. However, in the literature, a wide chasm exists between these two families of methods, and their relationship to each other is not well understood. Driven by this divide, we propose a unified framework and provide both theoretical analysis and practical recommendations under various cognitive diagnosis settings.PhDStatisticsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/174627/1/chenchma_1.pd
GAS-PHASE CONFORMATIONS AND ENERGETICS OF PROTONATED 2_-DEOXYADENOSINE-5_-MONOPHOSPHATE AND ADENOSINE-5_-MONOPHOSPHATE: IRMPD ACTION SPECTROSCOPY AND THEORETICAL STUDIES
No full textNature uses protonation to alter the structures and reactivities of molecules to facilitate various biological functions and chemical transformations. For example, in nucleobase repair and salvage processes, protonation facilitates nucleobase removal by lowering the activation barrier for glycosidic bond cleavage. Systematic studies of the structures of protonated 2'-deoxyribonucleotides and ribonucleotides may provide insight into the roles protonation plays in altering the nucleobase orientation relative to the glycosidic bond and sugar puckering. In this study, infrared multiple photon dissociation (IRMPD) action spectroscopy experiments in conjunction with electronic structure calculations are performed to probe the effects of protonation on the structures and stabilities of -deoxyadenosine--monophosphate (pdAdo) and adenosine--monophosphate (pAdo). Photodissociation as a function of IR wavelength is measured to generate the IRMPD action spectra. Geometry optimizations and frequency analyses performed at the B3LYP/6-311+G(d,p) level of theory are used to characterize the stable low-energy structures and to generate their linear IR spectra. Single point energy calculations performed at the B3LYP/6-311+G(2d,2p) and MP2(full)/6-311+G(2d,2p) levels of theory provide relative stabilities of the optimized conformations. The structures accessed in the experiments are determined by comparing the calculated linear IR spectra for the stable low-energy conformers computed to the measured IRMPD action spectra. The effects of the -hydroxyl moiety are elucidated by comparing the structures and IRMPD spectra of [pAdo+H] to those of its DNA analogue. Comparisons are also made to the deprotonated forms of these nucleotides and the protonated forms of the analogous nucleosides to elucidate the effects of protonation and the phosphate group on the structures.Made available in DSpace on 2016-01-05T20:07:11Z (GMT). No. of bitstreams: 3
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Dynamic analysis of extended bistable reeled fibre-reinforced composite booms for space applications.
No full textBistable Reeled Composite (BRC) booms have the potential to be used as lightweight structural elements for a number of space applications. This thesis details an approach for increasing the natural frequency and stiffness of extended BRCs. The motivation for this research is the desire to increase the scalability of a flexible “roll-up” solar array
which, in its deployed state, consists of two cantilevered BRCs supporting a flexible Photo Voltaic (PV) cell-covered blanket betwee n them. A parametric study has been presented, which analysed the effects of design parameters on the vibration characteristics of a single boom using a Finite Element (FE) approach. A numerical model was combined with a nonlinear constrained optimisation to maximise the natural frequency of BRC booms with respect to the fibre orientation angles and ply discontinuity locations, under the constraints of the physically achievable braid angles and constant coiled diameters resulting from the deployment mechanism design. The results demonstrate that careful selection of the fibre orientation angles and introducing a step change in the number of plies at strategic positions along the boom length can significantly increase the natural frequency. For instance, the natural frequency of a four-carbon/epoxy-nominalbraid-ply boom (L = 5.1 m, R = 38 mm, and β = 345◦) has been improved by more than 50%. The agreement between the natural frequency values for the complete solar array and the corresponding individual BRC booms indicates that the optimised solutions for a single boom model are applicable to the complete model for the first (cantilever) mode.
Experimental verification of the vibration characteristics of optimised BRC booms has
also been conducted. Finally, a dynamic stability analysis of the optimised BRC booms
under bending has been carried out using FE simulation, to quantify the maximum angular acceleration that they can withstand before failure. The optimised BRC booms
exhibit a higher resistance to bending during a spacecraft manoeuvre
Pharmacokinetics and pharmacodynamics of linezolid in plasma/cerebrospinal fluid in patients with cerebral hemorrhage after lateral ventricular drainage by Monte Carlo simulation
No full textXiaofei Wu,1 Yan Tang,1 Xiaohua Zhang,1 Chenchen Wu,2 Lingti Kong3 1Department of Emergency Internal Medicine, the First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, People’s Republic of China; 2Department of Endocrinology, the First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, People’s Republic of China; 3Department of Pharmacy, the First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, People’s Republic of China Objective: We investigated the pharmacokinetic (PK) and pharmacodynamic (PD) parameters of linezolid in patients who had suffered cerebral hemorrhage after lateral ventricular drainage. Materials and methods: Ten patients with cerebral hemorrhage after lateral ventricular drainage with stroke-associated pneumonia who were given linezolid were enrolled. Plasma and cerebrospinal fluid (CSF) samples were taken at appropriate intervals after the first administration of linezolid and assayed by high-performance liquid chromatography (HPLC). Then, PK parameters were estimated, and a Monte Carlo simulation was used to calculate the probability of target attainments (PTAs) for linezolid achieving the PK/PD index at different minimal inhibitory concentrations (MICs). Results: The maximum concentration of linezolid in plasma and CSF was reached at 1.00 h and 3.10 h, respectively. The average penetration of linezolid in CSF was 56.81%. If the area under the plasma concentration vs time curve from zero to the final sampling time (AUC0–24 h)/MIC ≥ 59.1 was applied as a parameter, the PTA of linezolid in plasma could provide good coverage (PTA ≥ 90%) only for pathogens with a MIC of ≤2 µg/mL, whereas it could be achieved in CSF with a MIC of ≤1 µg/mL. If %T > MIC ≥ 40% was applied as a parameter, the PTA of linezolid in plasma/CSF could provide good coverage if the MIC was ≤4 µg/mL. Conclusions: For patients with infection of the central nervous system and who are sensitive to the drug, the usual dosing regimens of linezolid can achieve a good therapeutic effect. However, for critically ill or drug-resistant patients, an increase in dose, the frequency of administration, or longer infusion may be needed to improve the curative effect. Keywords: linezolid, cerebral hemorrhage, plasma, cerebrospinal fluid, pharmacokinetics, pharmacodynamics, Monte Carlo simulatio
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