“Exact” and Approximate Methods for Bayesian Inference: Stochastic Volatility Case Study

We conduct a case study in which we empirically illustrate the performance of different classes of Bayesian inference methods to estimate stochastic volatility models. In particular, we consider how different particle filtering methods affect the variance of the estimated likelihood. We review and compare particle Markov Chain Monte Carlo (MCMC), RMHMC, fixed-form variational Bayes, and integrated nested Laplace approximation to estimate the posterior distribution of the parameters. Additionally, we conduct the review from the point of view of whether these methods are (1) easily adaptable to different model specifications; (2) adaptable to higher dimensions of the model in a straightforward way; (3) feasible in the multivariate case. We show that when using the stochastic volatility model for methods comparison, various data-generating processes have to be considered to make a fair assessment of the methods. Finally, we present a challenging specification of the multivariate stochastic volatility model, which is rarely used to illustrate the methods but constitutes an important practical application.     

Analysis of Organophosphorous Pesticides Based on Housefly Acetylcholinesterase Using Sequential Injection Analysis

Organophosphorous pesticides were analyzed based on the inhibition of acetylcholinesterase (AChE) from housefly and the electric eel using a sequential injection analysis (SIA) system. This analytical system is fully computerized and is able to automatically monitor the pesticide residues in an assay cycle of 180 s including 30 s incubation time when the flow is stopped. The optimal operation conditions such as AChE, substrate, pH, flow rate, and stopping time were studied. The experimental setup gave good reproducibility with the linear ranges for paraoxon of 1–70 ppb and dichlorovos of 20–70 ppb. The detection limits of paraoxon and dichlorovos were 1 and 5 ppb, respectively. The AChE from housefly shows 10 times higher sensitivity than the enzyme from the eel for these pesticide determination in this system.     

Injection moulding of thermoplastics: Freezing of variable-viscosity fluids.

The injection moulding of thermoplastics involves, during mould filling, flows of hot polymer melts into mould networks, the walls of which are so cold that frozen layers form on them. An analytical study of such flows is presented here for the case when the Graetz number is small and the Nahme number is non-zero and can be large. Thus the flows are fully-developed and temperature differences due to heat generation by viscous dissipation are sufficiently large to cause significant variations in viscosity. Gz Graetz number - h half-height of channel or disc - h ^* half-height of polymer melt region in channel or disc - L length of channel or pipe - m viscosity shear-rate exponent - Na _Q Nahme number based on flowrate - Na _P Nahme number based on pressure drop - Na _PL lower critical value of Nahme number based on pressure drop - Na _PU upper critical value of Nahme number based on pressure drop - Na _P Nahme number based on pressure gradient - p pressure - P pressure drop - Q volumetric flowrate - r radial coordinate in pipe or disc - R radius of pipe - Re Reynolds number - R _i inner radius of disc - R ₀ outer radius of disc - R ^* radius of polymer melt region in pipe - T temperature - T _m melting temperature of polymer - T ₀ reference temperature - T _w wall temperature - u axial velocity in pipe or channel or radial velocity in disc - w width of channel - x axial coordinate in channel - y transverse coordinate in channel or disc - z axial coordinate in pipe - thermal conductivity of molten polymer - thermal conductivity of frozen polymer - heat capacity of molten polymer - viscosity temperature exponent - dimensionless transverse coordinate in channel or disc - ^* dimensionless half-height of polymer melt region in channel or disc - dimensionless temperature - ^* dimensionless wall temperature - µ viscosity of molten polymer - µ ₀ consistency of molten polymer - dimensionless pressure drop - dimensionless pressure gradient - density of molten polymer - dimensionless radial coordinate in pipe or disc - _i dimensionless inner radius of disc - ^* dimensionless radius of polymer melt region in pipe - dimensionless velocity     

Injection moulding of thermoplastics: Freezing of variable-viscosity fluids.

The injection moulding of thermoplastics involves, during mould filling, flows of hot polymer melts into mould networks, the walls of which are so cold that frozen layers form on them. An analytical study of such flows is presented here for the case when the Graetz and Nahme numbers are large and the Pearson number is small. Thus the flows are developing and temperature differences due to heat generation by viscous dissipation are sufficiently large to cause significant variations in viscosity (but the difference between the entry temperature of the polymer to a specific part of the mould network and the melting temperature of the polymer is not). Br Brinkman number - Gz Graetz number - h half-height of channel or disc - h ^* half-height of polymer melt region in channel or disc - L length of channel or pipe - m viscosity shear-rate exponent - Na Nahme number - p pressure - P pressure drop - Pe Péclet number - Pn Pearson number - Q volumetric flowrate - r radial coordinate in pipe or disc - R radius of pipe - Re Reynolds number - R _i inner radius of disc - R _o outer radius of disc - R ^* radius of polymer melt region in pipe - T temperature - T _ad adiabatic temperature rise - T _e entry polymer melt temperature - T _m melting temperature of polymer - T _max maximum temperature - T ₀ reference temperature - T _w wall temperature - flow-average temperature rise - u _r radial velocity in pipe or disc - u _x axial velocity in channel - u _y transverse velocity in channel or disc - u _z axial velocity in pipe - w width of channel - x axial coordinate in channel or modified radial coordinate in disc - y transverse coordinate in channel or disc - z axial coordinate in pipe - thermal conductivity of molten polymer - thermal conductivity of frozen polymer - scaled dimensionless axial coordinate in channel or pipe or radial coordinate in disc - ₀ undetermined integration constant - heat capacity of molten polymer - viscosity temperature exponent - dimensionless transverse coordinate in channel or disc - ^* dimensionless half-height of polymer melt region in channel or disc - H ^* scaled dimensionless half-height of polymer melt region in channel or disc or radius of polymer melt region in pipe - dimensionless temperature - ^* dimensionless wall temperature - scaled dimensionless temperature - numerical constant - µ viscosity of molten polymer - µ ₀ consistency of molten polymer - dimensionless pressure gradient - scaled dimensionless pressure gradient - density of molten polymer - dimensionless radial coordinate in pipe or disc - _i dimensionless inner radius of disc - ^* dimensionless radius of polymer melt region in pipe - dimensionless streamfunction - scaled dimensionless streamfunction - dummy variable - streamfunction - similarity variable - similarity variable     

Synthesis of polyphilic hexaazatrinaphthylenes and mesomorphic properties

Methodologies for the synthesis of polyphilic hexaazatrinaphthylenes (HATN) with reduced symmetry based on the sequential condensation reactions of 1,2-bisalkoxy-4,5-diaminobenzenes with either tetrahydroxy-1,4-quinone or hexaketocyclohexane are described. The synthesized HATN possesses improved mesogenic properties and is liquid crystalline at room temperature.     

Metal content variation in wastewater and biosludge from Bangkok's central wastewater treatment plants

The objectives of this study were to determine the metal contents and their variations in influent, effluent and biosludge, and to evaluate the potential environmental impact of biosludge generated from the Bangkok, Thailand central wastewater treatment plants. The variation in influent metal content was site-specific and could be related to the economic activities of small-scale companies. An activated sludge process could remove some level of the metal content via a combination of biological and physicochemical processes. The variation in metal removal efficiencies strongly depended upon the influent wastewater characteristics and composition. Metal occurrence in biosludge was similar to the metals found in the influent. Iron was the most abundant while Cd had the lowest occurrence. A longer excess sludge operational condition and storage time may increase metal contents in biosludge due to the decomposition of biodegradable organic matter by microorganisms. According to the speciation results, the biosludge studied had a low mobility and availability index, except the RK plant biosludge. Most trace metals of interest were in the less mobile and bioavailable forms. The most mobile exchangeable and moderately mobile carbonate fractions of Cd, Mn, Ni and Zn were relatively low (5–30%). Biosludge from RK had a total Cu concentration higher than the limits, and to some extent exchangeable and carbonate fractions that were relatively high (∼ 40%).     

石墨炉原子吸收光谱法钼涂层直接进样测定葡萄酒中的铝

主要应用了石墨炉原子吸收光谱法塞曼扣除背景方式,在镀钼涂层的平台石墨管中直接进样测定葡萄酒中的铝含量.研究了石墨炉各主要工作条件对吸光度的影响,确定了该方法的最佳条件:0-100μg/L范围内呈线性关系;仪器的检出限为1.7μg/L;应用此方法测定了几种不同样品中铝含量,测定值的相对标准偏差(n=10)在2.28%-3...     

流动注射分光光度法测定煤灰中的微量铀

在稀硝酸介质中,以2-(3-羧基苯偶氮)-7-(4-氯-2-膦酸基苯偶氮)-1,8-二羟基-3,6-萘二磺酸(CPA-mK)作为显色剂,建立了一种测定微量铀的流动注射分光光度法,在最佳实验条件下,该方法的线性范围为0-35mg/L,检出限为0.026mg/L,应用该方法测定煤灰样品中的铀,其相对标准偏差为1.8%-3....     

Colorless gigabit WDM-PON link using injection locking and electro-absorption transceiver

In this paper, a novel colorless wavelength division multiplexing-passive optical network (WDM-PON) system using injection locking and electro-absorption transceiver (EAT) is proposed and demonstrated experimentally. This system has advantages, high data transmission, small downlink signal effect to uplink signal and less polarization sensitivity, compared to the system using reflective semiconductor optical amplifier (RSOA). Downlink signal modulates the right side carrier of the double side band signal by using injection locking. EAT functions as both photo detector in downlink signal and modulator for uplink signal, simultaneously. A possible cross absorption modulation effect from the EAT is analyzed experimentally. Bidirectional transmission of 1.25 Gbps and 622 Mbps for downlink and uplink, respectively, were verified through 23 km standard single mode fiber (SSMF).     

Mining categorical sequences from data using a hybrid clustering method

The identification of different dynamics in sequential data has become an every day need in scientific fields such as marketing, bioinformatics, finance, or social sciences. Contrary to cross-sectional or static data, this type of observations (also known as stream data, temporal data, longitudinal data or repeated measures) are more challenging as one has to incorporate data dependency in the clustering process. In this research we focus on clustering categorical sequences. The method proposed here combines model-based and heuristic clustering. In the first step, the categorical sequences are transformed by an extension of the hidden Markov model into a probabilistic space, where a symmetric Kullback–Leibler distance can operate. Then, in the second step, using hierarchical clustering on the matrix of distances, the sequences can be clustered. This paper illustrates the enormous potential of this type of hybrid approach using a synthetic data set as well as the well-known Microsoft dataset with website users search patterns and a survey on job career dynamics.