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Purpose: The purpose of this study is to present a newly proposed and developed sorting algorithm-based merging weighted fraction Monte Carlo (SAMWFMC) method for solving the population balance equation for the weighted fraction coagulation process in aerosol dynamics with high computational accuracy and efficiency. Design/methodology/approach: In the new SAMWFMC method, the jump Markov process is constructed as the weighted fraction Monte Carlo (WFMC) method (Jiang and Chan, 2021) with a fraction function. Both adjustable and constant fraction functions are used to validate the computational accuracy and efficiency. A new merging scheme is also proposed to ensure a constant-number and constant-volume scheme. Findings: The new SAMWFMC method is fully validated by comparing with existing analytical solutions for six benchmark test cases. The numerical results obtained from the SAMWFMC method with both adjustable and constant fraction functions show excellent agreement with the analytical solutions and low stochastic errors. Compared with the WFMC method (Jiang and Chan, 2021), the SAMWFMC method can significantly reduce the stochastic error in the total particle number concentration without increasing the stochastic errors in high-order moments of the particle size distribution at only slightly higher computational cost. Originality/value: The WFMC method (Jiang and Chan, 2021) has a stringent restriction on the fraction functions, making few fraction functions applicable to the WFMC method except for several specifically selected adjustable fraction functions, while the stochastic error in the total particle number concentration is considerably large. The newly developed SAMWFMC method shows significant improvement and advantage in dealing with weighted fraction coagulation process in aerosol dynamics and provides an excellent potential to deal with various fraction functions with higher computational accuracy and efficiency. [ABSTRACT FROM AUTHOR]

A methodology for decomposing the effects of price promotions into brand switching, stockpiling, and changes in consumption is proposed. Brand-loyal customers stockpile for future consumption in response to price promotions. Heavy users of a product stockpile more compared to light users.

A new econometric model was developed to examine the price competion among gasoline retailers in Singapore, and also the impacts of their locations. it was revealed that demand for gasoline depends on the demographics of the area in which the retailers are located. The applications of the new model on policies are discussed.

A study on consumers' willingness to pay and compete in online auctions is examined. The impact of experience in bidding on their behavior too is described.

Purpose: The purpose of this paper is to study the soot formation and evolution by using this newly developed Lagrangian particle tracking with weighted fraction Monte Carlo (LPT-WFMC) method. Design/methodology/approach: The weighted soot particles are used in this MC framework and is tracked using Lagrangian approach. A detailed soot model based on the LPT-WFMC method is used to study the soot formation and evolution in ethylene laminar premixed flames. Findings: The LPT-WFMC method is validated by both experimental and numerical results of the direct simulation Monte Carlo (DSMC) and Multi-Monte Carlo (MMC) methods. Compared with DSMC and MMC methods, the stochastic error analysis shows this new LPT-WFMC method could further extend the particle size distributions (PSDs) and improve the accuracy for predicting soot PSDs at larger particle size regime. Originality/value: Compared with conventional weighted particle schemes, the weight distributions in LPT-WFMC method are adjustable by adopting different fraction functions. As a result, the number of numerical soot particles in each size interval could be also adjustable. The stochastic error of PSDs in larger particle size regime can also be minimized by increasing the number of numerical soot particles at larger size interval. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the aerosol dynamics of the particle coagulation process using a newly developed weighted fraction Monte Carlo (WFMC) method. Design/methodology/approach: The weighted numerical particles are adopted in a similar manner to the multi-Monte Carlo (MMC) method, with the addition of a new fraction function (α). Probabilistic removal is also introduced to maintain a constant number scheme. Findings: Three typical cases with constant kernel, free-molecular coagulation kernel and different initial distributions for particle coagulation are simulated and validated. The results show an excellent agreement between the Monte Carlo (MC) method and the corresponding analytical solutions or sectional method results. Further numerical results show that the critical stochastic error in the newly proposed WFMC method is significantly reduced when compared with the traditional MMC method for higher-order moments with only a slight increase in computational cost. The particle size distribution is also found to extend for the larger size regime with the WFMC method, which is traditionally insufficient in the classical direct simulation MC and MMC methods. The effects of different fraction functions on the weight function are also investigated. Originality Value: Stochastic error is inevitable in MC simulations of aerosol dynamics. To minimize this critical stochastic error, many algorithms, such as MMC method, have been proposed. However, the weight of the numerical particles is not adjustable. This newly developed algorithm with an adjustable weight of the numerical particles can provide improved stochastic error reduction. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the evolution and growth of aerosol particles in a turbulent planar jet by using the newly developed large eddy simulation (LES)-differentially weighted operator splitting Monte Carlo (DWOSMC) method. Design/methodology/approach: The DWOSMC method is coupled with LES for the numerical simulation of aerosol dynamics in turbulent flows. Findings: Firstly, the newly developed and coupled LES-DWOSMC method is verified by the results obtained from a direct numerical simulation-sectional method (DNS-SM) for coagulation occurring in a turbulent planar jet from available literature. Then, the effects of jet temperature and Reynolds number on the evolution of time-averaged mean particle diameter, normalized particle number concentration and particle size distributions (PSDs) are studied numerically on both coagulation and condensation processes. The jet temperature and Reynolds number are shown to be two important parameters that can be used to control the evolution and pattern of PSD in an aerosol reactor. Originality/value: The coupling between the Monte Carlo method and turbulent flow still encounters many technical difficulties. In addition, the relationship between turbulence, particle properties and collision kernels of aerosol dynamics is not yet well understood due to the theoretical limitations and experimental difficulties. In the present study, the developed and coupled LES-DWOSMC method is capable of solving the aerosol dynamics in turbulent flows. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to study the complex aerosol dynamic processes by using this newly developed stochastically weighted operator splitting Monte Carlo (SWOSMC) method.Design/methodology/approach Stochastically weighted particle method and operator splitting method are coupled to formulate the SWOSMC method for the numerical simulation of particle-fluid systems undergoing the complex simultaneous processes.Findings This SWOSMC method is first validated by comparing its numerical simulation results of constant rate coagulation and linear rate condensation with the corresponding analytical solutions. Coagulation and nucleation cases are further studied whose results are compared with the sectional method in excellent agreement. This SWOSMC method has also demonstrated its high numerical simulation capability when used to deal with simultaneous aerosol dynamic processes including coagulation, nucleation and condensation.Originality/value There always exists conflict and tradeoffs between computational cost and accuracy for Monte Carlo-based methods for the numerical simulation of aerosol dynamics. The operator splitting method has been widely used in solving complex partial differential equations, while the stochastic-weighted particle method has been commonly used in numerical simulation of aerosol dynamics. However, the integration of these two methods has not been well investigated. [ABSTRACT FROM AUTHOR]

Obesity is an important risk factor for OSA. This study aimed to assess the effect of weight reduction through a lifestyle modification program (LMP) on patients with moderate to severe OSA.

Energy generation and consumption are the main contributors to greenhouse gases emissions in California. Natural gas is one of the primary sources of energy in California. A study was recently conducted to develop current, reliable, and California-specific source emission factors (EFs) that could be used to establish a more accurate methane emission inventory for the California natural gas industry. Twenty-five natural gas facilities were surveyed; the surveyed equipment included wellheads (172), separators (131), dehydrators (17), piping segments (145), compressors (66), pneumatic devices (374), metering and regulating (M&R) stations (19), hatches (34), pumps (2), and customer meters (12). In total, 92,157 components were screened, including flanges (10,101), manual valves (10,765), open-ended lines (384), pressure relief valves (358), regulators (930), seals (146), threaded connections (57,061), and welded connections (12,274). Screening values (SVs) were measured using portable monitoring instruments, and Hi-Flow samplers were then used to quantify fugitive emission rates. For a given SV range, the measured leak rates might span several orders of magnitude. The correlation equations between the leak rates and SVs were derived. All the component leakage rate histograms appeared to have the same trend, with the majority of leakage rates <0.02 cubic feet per minute (cfm). Using the cumulative distribution function, the geometric mean was found to be a better indicator than the arithmetic mean, as the mean for each group of leakage rates found. For most component types, the pegged EFs for SVs of ≥ 10,000 ppmV and of ≥ 50,000 ppmV are relatively similar. The component-level average EFs derived in this study are often smaller than the corresponding ones in the 1996 U.S. Environmental Protection Agency/Gas Research Institute (EPA/GRI) study.Implications: Twenty-five natural gas facilities in California were surveyed to develop current, reliable, and California-specific source emission factors (EFs) for the natural gas industry. Screening values were measured by using portable monitoring instruments, and Hi-Flow samplers were then used to quantify fugitive emission rates. The component-level average EFs derived in this study are often smaller than the corresponding ones in the 1996 EPA/GRI study. The smaller EF values from this study might be partially attributable to the employment of the leak detection and repair program by most, if not all, of the facilities surveyed.

Much of the recent empirical IO research has been conducted in the context of relatively mature, stable (often consumer packaged goods) markets. In these markets, consumer preferences and competitive interaction are often characterized by relatively stable patterns over time. In contrast, modeling and estimating analogous patterns in rapidly changing technology-intensive industries, where brand preferences and technology evolve rapidly, can be challenging. Our primary objective in this research is to build on recent developments in econometric estimation and modeling to assess the time-varying shifts in consumer brand preferences in a rapidly changing technology industry. In doing so, we document an interesting technological conundrum—technological advancement can often lead to commoditization. In the Personal Computer (PC) market, this began with differentiation that was initially central to success in a market that has been increasingly commoditized over time. Methodologically, we adopt a factor-analytic approach to model and estimate the evolution of consumer brand preferences over time.

In this paper, we study the role of consumer price expectations in influencing consumer purchase decisions. Specifically, we examine the drivers of relative dominance of two price expectations—one formed prior to store visit (PRIOR) and the other about price in other stores (POST) formed after being exposed to focal store price. We collect the data from an online store shopping environment, allowing participants to make real purchase decisions. We have identified two distinct classes of shopping behaviors in our data—inside-focused(IF) and outside-looking(OL). Purchase decisions of the former are mainly driven by PRIOR while that of the latter by POST. At constant cost, we show that a promotion scheme with deep discounts (e.g., 5 % for 3 weeks or 15 % price cut in the first week) boosts sales more than the one with shallow discount (e.g., 3 % for 5 weeks). This increase comes mainly from the OL class, which is more sensitive to price changes. We further demonstrate how stores should manage consumer price expectations to maximize the sales lift during price promotions.

In the present study, the interaction effects of different vehicle speeds and vehicular exhaust tailpipe exit velocity conditions on the exhaust particle dynamic behaviors in the near-wake region behind the studied vehicle were numerically investigated. The results showed that the particles were drawn up into the recirculation region and then moved toward into the upper vortex by its lower vortex. A lower particle number concentration behind the studied vehicle is observed for a higher vehicle speed because of the rapidly increasing dilution ratio and the nucleation rate. The particle volume concentration is the highest in the recirculation region behind the studied vehicle and is diluted gradually beyond the recirculation region in the downstream.

To describe the type of complications related to contact lens wear seen in a hospital setting in Singapore.

Using micro‐level scanner data, I study empirically the consumer demand for soft drinks, which is characterized by multiple‐product, multiple‐unit purchasing behavior. I develop a continuous hedonic‐choice model to investigate how consumers choose the best basket of products to satisfy various needs. My model's embedded‐characteristics approach both helps to reduce the dimensionality problem in model estimation and generates flexible substitution patterns. Hence, the model is useful in application to data with many product choices that are correlated with each other at the individual level. The estimation results show that interesting substitutability and even a form of complementarity exist among soft drinks.

For a set A={A1,…, Am} of nX nmatrices with nonnegative integer entries, let P(A) be the set of all finite products of matrices in A. We show that there is a square space algorithm to decide, given A, whether or not P(A) is finite. As a corollary, we show that there is an exponential space algorithm to decide, given a nondeterministic Mealy sequential machine Mwith accepting states, whether there exists an integer d⩾0 such that on every input, the number of accepting computations of Mproducing distinct outputs is at most d. If dexists, the smallest such dcan be computed in space exponential in size(M)+log d. The space bound reduces to polynomial for the analogous problem of ambiguity of nondeterministic finite acceptors.

This paper describes the experience of primary cataract extraction and posterior chamber IOL implantation in 11 eyes with penetrating ocular trauma. The primary surgical procedure consisted of repair of corneoscleral laceration, cataract extraction, posterior chamber IOL implantation and in certain cases, removal of intraocular foreign body and vitrectomy. 10 out Of 11 cases had a post operative visual acuity of 6/18 or better, with 9 out of 11 having a post operative visual acuity of 6/12 or better. One case initially had a visual acuity of 6/24 but later developed retinal detachment with a visual acuity of ‘hand movements’. Another patient developed a small localised retinal detachment during the tenth postoperative month but with successful surgery, attained a visual acuity of 6/6. The encouraging results suggest that this procedure may be recommended in carefully selected cases, under the management of an experienced surgeon.

The Towers of Hanoi problem is analyzed with the aid of Hanoi graphs depicting legal configurations (i. e. arrangements of the disks on the pegs) and the transitions among them. Specifically, the mean and the standard deviation of the minimum numbers of moves required to change an arbitrary initial configuration into an arbitrary final configuration are computed, and are shown to be approximately 0.52655 · 2n and 0.25025 · 2n respectively for n disks.

In this paper we consider two-way counter machines, i.e., two-way finite automata with counters whose contents have no effect on transitions except that an attempt to decrement an empty counter will abort the computation. We show that the deterministic machines have an unsolvable emptiness problem, but that their universe problem is solvable because they accept languages whose complements are context free. In the nondeterministic case, we show that these machines are equivalent to two-way nondeterministic logspace Turing machines, and establish an infinite hierarchy based on the number of weak counters. Finally, we disprove two conjectures concerning the nondeterministic machines.

The article discusses about the disease, infective endopthalmitis. It touches on the severity of the disease and how it requires prompt diagnosis and treatment.