First-order Analysis Research Articles

First-Order Bayesian Regret Analysis of Thompson Sampling

We address online combinatorial optimization when the player has a prior over the adversary’s sequence of losses. In this setting, Russo and Van Roy proposed an information theoretic analysis of Thompson Sampling based on the information ratio, allowing for elegant proofs of Bayesian regret bounds. In this paper we introduce three novel ideas to this line of work. First we propose a new quantity, the scale-sensitive information ratio, which allows us to obtain more refined first-order regret bounds (i.e., bounds of the form <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$O(\sqrt {L^{*}})$ </tex-math></inline-formula> where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L^{*}$ </tex-math></inline-formula> is the loss of the best combinatorial action). Second we replace the entropy over combinatorial actions by a coordinate entropy, which allows us to obtain the first optimal worst-case bound for Thompson Sampling in the combinatorial setting. We additionally introduce a novel link between Bayesian agents and frequentist confidence intervals. Combining these ideas we show that the classical multi-armed bandit first-order regret bound <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ \widetilde {O}(\sqrt {d L^{*}})$ </tex-math></inline-formula> still holds true in the more challenging and more general semi-bandit scenario. This latter result improves the previous state of the art bound <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ \widetilde {O}(\sqrt {(d+m^{3})L^{*}})$ </tex-math></inline-formula> by Lykouris, Sridharan and Tardos. Moreover we sharpen these results with two technical ingredients. The first leverages a recent insight of Zimmert and Lattimore to replace Shannon entropy with more refined potential functions in the analysis. The second is a Thresholded Thompson Sampling algorithm, which slightly modifies the original algorithm by never playing low-probability actions. This thresholding results in fully <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T$ </tex-math></inline-formula> -independent regret bounds when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L^{*}\leq \overline {L} ^{*}$ </tex-math></inline-formula> is almost surely upper-bounded, which we show does not hold for ordinary Thompson Sampling.

Nonparametric estimation of the intensity function of a spatial point process on a Riemannian manifold

Summary This paper is concerned with nonparametric estimation of the intensity function of a point process on a Riemannian manifold. It provides a first-order asymptotic analysis of the proposed kernel estimator for Poisson processes, supplemented by empirical work to probe the behaviour in finite samples and under other generative regimes. The investigation highlights the scope for finite-sample improvements by allowing the bandwidth to adapt to local curvature.

Probabilistic Slope Seepage Analysis under Rainfall Considering Spatial Variability of Hydraulic Conductivity and Method Comparison

Due to the spatial variability of hydraulic properties, probabilistic slope seepage analysis becomes necessary. This study conducts a probabilistic analysis of slope seepage under rainfall, considering the spatial variability of saturated hydraulic conductivity. Through this, both the commonly used Monte Carlo simulation method and the proposed first-order stochastic moment approach are tested and compared. The results indicate that the first-order analysis approach is effective and applicable to the study of flow processes in a slope scenario. It is also capable of obtaining statistics such as mean and variance with a high enough accuracy. Using this approach, higher variabilities in the pressure head and the fluctuation of the phreatic surface in the slope are found with a higher value of the correlation length of the saturated hydraulic conductivity. The Monte Carlo simulation is found to be time-consuming: at least 10,000 realizations are required to reach convergence, and the number of realizations needed is sensitive to the grid density. A coarser grid case requires more realizations for convergence. If the number of realizations is not enough, the results are unreliable. Compared with Monte Carlo simulation, the accuracy of the first-order stochastic moment analysis is generally satisfied when the variance and the correlation length of the saturated hydraulic conductivity are not too large. This study highlights the applicability of the proposed first-order stochastic moment analysis approach in the slope scenario.

Modeling Negotiating Abilities in the Construction Sector: A Proposed Mathematical Model Using the Confirmatory Factor Analysis Method

This study aims to develop a mathematical model for evaluating the objective abilities needed for negotiation and to provide a tool that companies can use to select a negotiation team. The model was constructed using a Likert pentagonal scale, where numbers from 5 to 1 represented the level of agreement or disagreement, and seven objective abilities were considered, including analytical ability, economic knowledge, legal knowledge, linguistic ability, psychological understanding, normative understanding, and general knowledge. The model was tested using a structured interview (sixteen interviews) with experts and specialists in the construction industry as a case study and then validated by quantitative data analysis method using first-order confirmatory factor analysis (CFA) with a sample of consultants (220 responses) from companies and offices related to the construction sector. The study found that the model is valid for use in the construction industry and can be useful for selecting negotiators. The developed model can be used, adapted, and modified according to the needs of different negotiation situations. This research is the first of its kind to develop a mathematical model for evaluating negotiating abilities and can be used as a model for similar research studies.

Development of Summative Assessment Instruments for the Affective Aspects of Learning History

Instruments for measuring both the affective and psychomotor aspects of teaching are required. The study's overarching goal is to create a reliable and valid assessment tool for measuring affective competency (values contained in history). Nine hundred thirty-five students from Medan's XI Social Sciences high school participated as research subjects. An affective aspect assessment sheet, which is a questionnaire with various statements to gauge affective aspects, was used to collect research data. To compare measurement models and make it simpler to analyze model correctness, structural equation modelling (SEM) analysis with first- and second-order components was employed in the data analysis. The findings of the first-order confirmatory factor analysis using the ML (maximum likelihood) technique indicated that all items had a correlation coefficient greater than 0.32, and the results of testing using the model had a significance level of 0.0001, according to the research analysis. The structural equation model (SEM) findings, with support from second-order structures, are also estimated with adequate theoretical confidence. The construct reliability (CR) and variance extract (VE) coefficients indicate that the designed instrument complied with the reliability coefficient acceptability limits of 0.70 for CR and 0.50 for VE. The development process resulted in an affective competency assessment tool with 84 valid and reliable items spread across 5 dimensions and 14 indicators. The instruments created were therefore shown to be valid and reliable for assessing affective aspects of learning history. The findings of this study are utilized to diagnose student potential, particularly concerning affective components, so that students are aware of their strengths and weaknesses. The findings of this study are utilized by stakeholders as input for policymaking, particularly in the area of education.

Along-Track Boundedness Condition for Spacecraft Relative Motion Around a Slowly Rotating Asteroid

In this paper, the closed-form along-track boundedness condition for spacecraft relative motion around a slowly rotating asteroid is presented. As opposed to the previously proposed criteria where three necessary constraints must be satisfied, the current approach only requires to enforce one constraint to suppress the along-track drift, thus allowing two additional degrees of freedom in spacecraft formation design. In particular, to adapt the derived results applicable for formation with a relatively large size, the boundedness condition via first-order analysis is then extended to obtain a second-order result. In the latter case, the value of mean semimajor axis difference is found to be the root of a quadratic (algebraic) equation. Moreover, an optimal single-impulse maneuver is analyzed, by means of which the bounded relative motion can be guaranteed in the presence of initialization errors. Illustrative examples are provided to validate the analytical results.

Evaluation of Stability Resistance Factor for Slender Concrete Columns Internally Reinforced with Fiber-Reinforced Polymer Bars

The validity of the stability resistance factor in the moment magnification procedure for the analysis of slender columns reinforced with fiber-reinforced polymer (FRP) bars (FRP-RC columns) has not yet been considered in the literature. The development of such a factor, compatible with current building codes, is discussed in this paper. In the development process, first, the variability of the ultimate strength of slender FRP-RC columns was investigated, and the effect of variations in geometric and material properties on this variability was determined. The results of the variability study were later used in the first-order reliability analysis to estimate the appropriate stability resistance factor. The results of the analysis show that a stability resistance factor of 0.75 or 0.7, depending on the flexural stiffness expression, is representative of typical slender FRP-RC columns. Thus, we propose the use of this value, in combination with the recommended load factors.

Enhancement of perpendicular magnetic anisotropy and formation of interface in Nd-Dy-Fe-Co-B thick film with Ta spacer layer

The perpendicular magnetic anisotropy of Nd-Fe-B films decreases when the film thickness increases above a critical value, owing to the formation of the in-plane texture. To avoid this dilemma, the influences of Ta spacer layers on the microstructure and magnetic properties of Nd-Dy-Fe-Co-B thick films are systematically investigated by varying the number and thickness of Ta spacer layers. With increasing the number and thickness of Ta spacer layers, a great enhancement of the perpendicular magnetic anisotropy is found, while the coercivity maintains around 2 T. According to the analysis of microstructural results, some interfaces are formed, with the Nd-Fe-B columnar crystal and the Nd element aggregation area being the two sides of the interface. It is found that the Ta spacer layer facilitates the formation of the out-of-plane texture. In addition, the Ta spacer layer has the effect of enhancing the pinning effect leading to a high coercivity. Based on first-order reversal curve analysis, the Ta spacer layer can enhance the dipole interaction and reduce the exchange interaction, which reveals that Nd-Fe-B grains are isolated by the Nd-rich phase. This work can help us to prepare thick Nd-Fe-B-based films with high perpendicular magnetic anisotropy and high coercivity for applications in micromechanical systems.

Optimal source–sink matching and prospective hub–cluster configurations for CO 2 capture and storage in India

Abstract At COP26, India announced strong climate commitments of reaching net-zero greenhouse gas emissions by 2070. Meeting this target would likely require substantial deployment of CO 2 capture and storage (CCS) to decarbonize existing large-point sources of CO 2 . This study attempts to evaluate opportunities for deployment of CCS in India in the forthcoming decades. A geographic information system-based approach was adopted for mapping existing sources of CO 2 with the sinks. The results show that regionally-appropriate ways of moving towards CCS at scale exist in both the power and industrial sectors. Coupled analysis of these sectors with sinks shows that eight clusters may be developed throughout the country to sequester 403 Mt-CO 2 annually. These clusters are concentrated near Category-I oil basins and the Category-I coalfields (Damodar Valley), which may also create suitable financial incentives by incremental oil and coalbed methane recovery, respectively. Furthermore, a first-order costing analysis evaluates that the cost of avoidance across basins may range from –$31 to $107/t-CO 2 , depending on the type of storage reservoir and the proximity to large-point sources. A total of 12 suitable hubs and clusters were created based on annual emissions above 1 Mt-CO 2 of each large-point source and their proximity with geological sinks.

3-D Supramolecular, quantum computational, and vibrational spectroscopic investigation on L-cysteinium methanesulfonate single crystals

This article reports on molecular modeling using density functional theory (DFT) performed on L-cysteinium methanesulfonate (L-CMS). Calculations were performed on the B3LYP/LanL2DZ level with 6-31 G(d,p) basis set using the Gaussian 09 program package. The optimized structure, HOMO-LUMO, energy gap, electronic properties, MEP, dipole moment, first-order molecular hyperpolarizability (β), chemical potential, global hardness, softness, global electrophilicity, and natural bond orbital analysis of this compound were studied by computational procedures. Intermolecular O-HO, N-HO, and S-HO hydrogen-bonding interactions with different motifs were observed in the crystal structure. Hirshfeld surface analyzes were also performed. Energy frameworks have been constructed to understand the packing of molecules by examining the different intermolecular interaction energies.

Effect of the implosion of a deep-sea pressure hull on surrounding structures

A shock wave is generated when a pressure hull implodes in a deep-sea environment, and such an implosion can jeopardise the safety of a deep-sea submersible. However, the damage caused to surrounding structures by the implosion of a high-strength, deep-sea pressure hull has not yet been reported. Therefore, in the present study, the aforementioned aspect was investigated by causing the implosion of a scaled-down submersible pressure hull model in an ultra-high-pressure chamber. A numerical method was developed to predict the multiphase coupling interactions between liquid, gaseous, and solid for two deep-sea pressure hulls. The geometric imperfection of pressure hulls is considered in this method, the first-order linear buckling modal analysis is carried out to simulate initial geometric imperfections. The effect of the shock wave caused by the implosion of one of the pressure hulls on the other pressure hull located nearby was investigated. Moreover, the stress and displacements of characteristic points on the two pressure hulls were examined. The variation in the strain energy of the surrounding pressure hull under pressure hull implosion was also analysed.

A numerical strategy for relieving pretension of cable net structures by exchanging stiffness components

Cable net structures are generally highly tensioned to resist the deformation induced by external loads, while the peripheral structural members are heavily burdened to balance the pretension. A numerical strategy is proposed to relieve the pretension without changing the structural geometry and deformation by exchanging the stiffness components, i.e., the structural elastic stiffness and geometrical stiffness. Based on the eigen-decomposition of the tangent stiffness matrix, the stiffness resistance to the deformation generated by a dominant load is quantified for any direction of eigenvector. The key structural stiffness is therefore defined and characterized by those eigenvalues and their corresponding eigenvectors with significant stiffness resistances. The contributions to the key structural stiffness are evaluated for the structural elastic stiffness and geometrical stiffness, respectively, and whether the decrease in key structural stiffness due to the pretension reduction can be compensated with the elastic stiffness by changing the cross-sectional areas of cables is analyzed. Then, the variations in isolated or closely spaced eigenvalues and their corresponding eigenvectors are estimated based on the first-order perturbation analysis of the tangent stiffness matrix. The underdetermined system of linear equations between the adjustments of the cross-sectional areas of cables and the expected variation in the key structural stiffness is established, and its least squares solution is employed to minimize the rehabilitation cost of the key structural stiffness. The proposed numerical strategy is applied to rehabilitate the key structural stiffness of an illustrative saddle-shaped cable net structure, whose pretension is proportionally decreased to different levels, by adjusting the cross-sectional areas of cables, and its accuracy and validity are verified. The applicability of the numerical strategy is also discussed in terms of the contribution coefficient of elastic stiffness to the key structural stiffness and the magnitude of pretension reduction.

Adaptation of the Global Motivation Scale (GMS-28) in Indonesian Version

Motivation is one of the important variables for study, whereas many motivational studies have been conducted to predict learning, performance, and behavior change. The motivational scale that has gone through psychometric testing is required in motivational research to accurately describe the construct. There is still low availability of motivational scale in Indonesia that has passed the psychometric testing. Therefore, this study aims to adapt the Global Motivation Scale (GMS-28) into Indonesian. The adaptation process refers to the adaptation guidelines by the International Test Commission, where the process of adaptation also involves psychometric testing. Data collection was carried out using an online questionnaire on 383 participants aged 18-25 years. The psychometric test was carried out using internal consistency reliability and validity based on internal structure. The internal consistency scale has revealed all acceptable reliability coefficients aspects with a range of a = 0.703 – 0.810. Item analysis pointed out that all items have good item-total correlation and item mean. Findings from First-order Confirmatory Factor Analysis showed that all aspects have acceptable model fit and all of the items significantly measures the aspects on GMS-28. Based on these results, it can be concluded that the Indonesian version of the GMS-28 is suitable for use for further studies. However, further testing needs to be done using a larger sample to be used in all Indonesian populations.

Failure analysis on fully-transparent deep-sea pressure hulls used at 2,500 m depth

Fully-transparent deep-sea pressure hulls have been attracted attention in recent years with the increasing demand for underwater observation. So far, public researches on design rule and failure modes for fully-transparent deep-sea pressure hulls are limited and the relevant experience cannot meet the requirements of new cabin design. In this study, the compression test is carried on, in which the material samples are subjected to quasi-static compressive load until failure in tests at different loading rates, and the hyperelastic finite element model is established in LS-DYNA software to simulate the failure process. Simulation results of material properties in finite element analysis on the cylindrical samples are compared with the experimental data, including the characteristic points of the mechanical properties in elastic stage and hardening stage, the ultimate load and failure mode of the samples. Mesh convergence analysis is conducted, and the appropriate mesh quality is accordingly selected in simulation of fully-transparent deep-sea pressure hulls. An equation for prediction of instability-type failure is described, which is derivation based on the classical analytical expression of elastic instability, thus, when 5 times of safety factor is taken, the wall thickness of the pressure hull is calculated to be t/R0 = 0.0685 at 2,500 m depth. Ultimate strength and failure mode of a typical fully-transparent deep-sea pressure hull are simulated. First, the first-order linear buckling modal analysis is carried out to simulate initial geometric imperfections. Then, simulations for the loading and collapse process of two fully-transparent pressure hulls respectively with one opening and two openings are conducted, and the ultimate load of 126 MPa and 128 MPa for the two kinds of hulls are obtained. Finally, simulation of a scaled pressure hull is carried out and simulation results are compared with the experimental data in reference, which are basically consistent. The calculated failure strength shows that the spherical hulls satisfy the safety factor requirement of 5 times. The provided simulation procedure can be referred for failure analysis of fully-transparent pressure hulls.

Measures of Naturalistic Language for Dialect-Speaking Children: The Case of Cypriot Greek

The aim of this study was to longitudinally examine mean length of utterance in words (MLU-w) and number of different words (NDW) and their association in children speaking Cypriot Greek (CG), a dialect for which such measures of language development have not been adequately investigated. Language samples from 36 typically developing monolingual CG-speaking children were collected at 4-month intervals from the age of 3;0 until 4;0 through free-play based conversation between the children and their caregivers. A zero-order correlation analysis among MLU-w, NDW, and age showed strong positive correlations between any two of these measures. A first-order analysis controlling for age showed that the correlation between MLU-w and NDW was independent from the influence of age. The study provides valuable information on the correlation between MLU-w and NDW for CG-speaking children and it contributes to our knowledge about language development in a dialectal variety lacking standardised tests.

On the ferrite-controlled iron coupling for enhanced soft magnetic hybrid composites via first-order reversal curves

The substitution of conventional non-magnetic binder in soft magnetic iron composites by insulating spinel ferrite has been proven as a powerful avenue for enhancing the interparticle coupling while suppressing eddy currents. The inherent shortcomings of macroscopic characterization, hindering the phase- and magnetization process-resolved reconstruction, are overcome by generalized application of the first-order reversal curves analysis for the first time. The mechanism of involving ferrite coating as a true matrix, evolving from the beneficial coupling effect at low concentrations towards the reappearing demagnetizing interactions that trigger a partial decoupling at higher fractions, is evidenced in the computed diagrams encompassing the microscopic switching. This substantial improvement is related to a thin and uniform layer of submicron ferrite grains, occupying less than 5 vol% of bulk composite, which compensates the free magnetic poles at the surface of iron particles and restrains the action of local anisotropic demagnetizing field. A significant constriction of switching and interaction field distributions in ferrite-coated iron composites with respect to a ferrite-free system is modeled and the conditions for having amplified interphase coupling are defined. We further demonstrate that heterogeneous switching of core particles and their shell provides an efficient way of manipulating the domain walls activity with increasing prevalence of spin rotations with excessive content of ferrite.

Karakterizacija suvog kliznog ponašanja Si-Mo-Cr nodularnog livenog gvožđa

The prerequisites for a brake disc material include a lower specific wear rate, a high coefficient of friction against brake pad material, lighter weight, and a higher heat dissipation rate. The present research studied the dry sliding wear behavior of as-cast Si-Mo-Cr ductile cast iron (DCI). A series of pin-on-disc wear tests are conducted using Taguchi L16 array for the optimum combination of load, sliding velocity, and temperature on a rotary tribometer setup at controlled temperatures ranging from 30°C to 240°C. The analysis of variance, first-order regression analysis, and confirmation tests are done to validate the results obtained for the material's wear properties. SEM and EdX analysis of wear surfaces is also done. It founds that the sliding velocity has a more significant influence on the specific wear rate. In contrast, the applied load is the key influencing parameter for a higher value of the coefficient of friction.

A Closed-Form Solution for Source Localization Using FDOA Measurements Only

This letter focuses on source localization using frequency difference of arrival (FDOA) measurements only. An efficient two-step weighted least square (TSWLS) method is proposed to estimate the unknown source position in closed form. In its first step, intermediate variables are introduced to pseudo-linearize FDOA equations. In the second step, the source position estimate is updated from solution equations established by using the first-order perturbation analysis. Theoretical analysis and numerical results have demonstrated the efficiency of the proposed method.

증강현실 기반 가상피팅시스템 사용시 지각된 기술 속성의 다차원성 : 위계적 요인구조모델 분석

The purpose of this study was to identify the underlying dimensions of AR technological attributes (ARTA), and estimate the hierarchical factor models for using a virtual fitting system in fashion retailing. The sample in this study consisted of consumers in their 20s and 30s. A total of 173 usable responses were obtained from volunteers who agreed to participate in the lab experiments and a survey with a questionnaire. The first-order confirmatory factor analysis confirmed that perceived ARTA consisted of five factors: augmentation, vividness, visual comfort, responsiveness, and organized system in using the virtual fitting system. Also, the estimated second-order factor model showed that the five ARTA factors were predicted by higher-order two constructs: the first

First-order analyses on the role of surface wind in the long-term contraction of the Indo-Pacific warm pool

Due to its high evaporation rate, the Indo-Pacific Warm Pool (IPWP) is one of the most important drivers of Indonesian weather and climate. Previous studies, based on the Sea Surface Temperature (SST) proxy records, suggest that IPWP in the mid-Holocene era (~6000 years ago) underwent a contraction (colder on its east-west perimeter and warmer on its center) compared to today’s condition. In this research, the role of surface wind in contracting the IPWP was analyzed by checking the coherency between changes in SST, wind-stress magnitude, and evaporation. The Climate Community System Model version 4 (CCSM4) simulated these three physical quantities under the pre-Industrial and mid-Holocene scenarios. In these simulations, an anti-phase relation between SST and wind-stress magnitude indicates an important role for a weaker surface wind in warming the SST in the center of the IPWP (South China Sea and Banda Sea), mainly during boreal autumn. However, a weaker surface wind did not seem to have simultaneously suppressed ocean evaporation to warm the SST, as shown by the phase-lag relation in their monthly climatology. On the other hand, colder SSTs on the east-west perimeter of the IPWP (western coast of Sumatra and northern coast of Papua) are unlikely to be associated with changes in the surface wind following a weak correlation between their SST and wind-stress magnitude