Publications

A spatiotemporal model is postulated and estimated using a procedure that infuses the forward search algorithm and maximum likelihood estimation into the backfitting framework. The forward search algorithm filters the effect of temporary structural change in the estimation of covariate and spatial parameters. Simulation studies illustrate capability of the method in producing robust estimates of the parameters even in the presence of structural change. The method provides good model fit even for small sample sizes in short time series data and good predictions for a wide range of lengths of contamination periods and levels of severity of contamination.

A procedure for estimating a time series model with structural change is proposed. Nonparametric bootstrap (block bootstrap or AR sieve) is applied to a series of estimates obtained through a modified forward search (FS) algorithm. The FS algorithm is implemented with overlapping and independent blocks of time points. The procedure can mitigate the difficulty in estimating when there is a temporary structural change. The simulation study indicated robustness of estimates from the estimation method when temporary structural change is introduced into the model provided that the time series is fairly long. As the effect of structural change persists in a longer period, the robustness of the bootstrap methods is further emphasized. We also provided a procedure for detecting the structural change and the subsequent adjustment of the overall model if indeed, there is a structural change.

We used simulated data to investigate both the small and large sample properties of the within-groups (WG) estimator and the first difference generalized method of moments (FD-GMM) estimator of a dynamic panel data (DPD) model. The magnitude of WG and FD-GMM estimates are almost the same for square panels. WG estimator performs best for long panels such as those with time dimension as large as 50. The advantage of FD-GMM estimator however, is observed on panels that are long and wide, say with time dimension at least 25 and cross-section dimension size of at least 30. For small-sized panels, the two methods failed since their optimality was established in the context of asymptotic theory. We developed parametric bootstrap versions of WG and FD-GMM estimators. Simulation study indicates the advantages of the bootstrap methods under small sample cases on the assumption that variances of the individual effects and the disturbances are of similar magnitude. The boostrapped WG and FD-GMM estimators are optimal for small samples.

In this exploratory study, I investigated lived experiences of unrequited love among young Filipino gay men in order to explore unrequited love beyond its heteronormative forms. Analysis of qualitative accounts from 11 out gay men who participated in focus groups indicated that unrequited love was a highly meaningful subjective experience involving a spectrum of negative affect, uncertainty, and self-esteem lowering. Non-reciprocity was often attributed to a lack of matching on dimensions like availability, sexual orientation, relationship goals, and personality. Non-homophobic social support was important in the reduction of uncertainty and management of distress, in addition to other strategies for coping with rejection and non- formation of the desired love relationship.

Economics is said to be the ‘science of choice’, stereotypically focused on the area of activity/behavior that emerges from interactions between entities offering things up for sale and the consumers choosing among the available options. The economistic assumption is that such choices are to be based on ‘self-interest’ or the search for the most profitable exchange. Starting from this, this paper explores the ‘market’ for Anthropology as seen in the results of a 2004 survey by UP Mindanao, and in decision trees modeling the rationality in selecting their degree courses made by UP Diliman students who were taking up Economic Anthropology. (Both projects also conducted by students as pedagogical/educational exercises in social science and anthropology.)

Two bootstrap procedures are introduced into the hybrid of the backfitting algorithm and the Cochrane–Orcutt procedure in the estimation of a spatial-temporal model. The use of time blocks of consecutive observations in resampling steps proved to be optimal in terms of stability and efficiency of estimates. Between iterations, there were minimal changes in the empirical distributions of the parameter estimates associated with the covariate and temporal effects indicating convergence of the algorithm. Crop yield data are used to illustrate the proposed methods.

The simulation study indicated that prediction error from the fitted model (estimated from either Method 1 or Method 2) is very low. Also, the prediction error is relatively robust to the number of spatial units and the number of time points.

Ortho-type UP resin is reinforced with long abaca and short bagasse fibers to produce a novel type of natural fiber-reinforced (NFR) hybrid composite material that is environment-friendly, has a long service life, possesses the properties of both long and short FRP’s, and has also acquired the advantages of utilizing two different types of natural fiber reinforcements. The abaca and bagasse fibers are treated in 5wt% NaOH(aq) solution at 80°C for 9 hours and pressed into continuous, unidirectional fiber sheets and random fiber mats, respectively. The fibers are then incorporated into the resin matrix by hand lay-up method, producing FRP laminates with the same uniform thickness but subjected to varying fiber loading conditions: (1) the stacking of long fiber sheets are done in cross-ply and parallel orientation; (2) the abaca and bagasse fibers are stacked in different alternating sequence patterns, and (3) the fibers are added into the ortho-UP matrix at increasing fiber fraction. The alkali-treated FRP laminates show an increase in fiber-matrix interfacial adhesion as compared to the untreated FRP’s, based on the overall improvement in the composite mechanical strength, as well as from the lesser visible fiber pull-out observed from SEM images on their fracture surfaces. Also, as expected, the tensile and flexural strengths of the abaca/bagasse hybrid FRP measures intermediate to those of abaca and bagasse FRP’s. The strength has also improved with increasing fiber content, although this increase has also caused an increased occurrence of void spaces that may consequently become detrimental to the NFR composite’s performance.