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Mengistu D.A.,Bahir Dar University | Waktola D.K.,Los Angeles Mission College
Journal of Land Use Science | Year: 2016

To monitor land-use/land-cover (LULC) change and assess its impact on the soil property, the availability of benchmark data is indispensable, which is hardly available in the intensively cultivated regions of developing countries. Our study attempts to solve this problem by generating a benchmark soil data through the development of modified spatial analogue (MSA) method in the context of the Upper Dijo River catchment, south-central Ethiopia. The magnitude and patterns of LULC changes were extracted from air photos and satellite imageries, along with the acquisition of soil samples from the reference and target sites through ground survey. Analysis of digital image processing shows significant LULC changes in a period that spanned three decades. The impact of LULC change on soil quality was assessed by comparing the soil physico-chemical properties sampled from the reference and target sites. The result shows a decline in total nitrogen, organic matter, available potassium and pH levels in soils collected from target sites, which conforms to results reported by studies conducted in data-rich environment. With careful validation, MSA could be useful for monitoring soil property changes in data-scarce environment and generate soil-related parameters for agro-ecological models. © 2014 Taylor & Francis. Source

Zhang T.-Y.,University of California at Los Angeles | Ji S.,Los Angeles Mission College | Bozovic D.,University of California at Los Angeles
PLoS ONE | Year: 2015

Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection. One of the manifestations of the active process is the occurrence of spontaneous hair bundle oscillations in vitro. Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics. We used microbeads to connect small groups of hair cell bundles, using in vitro preparations that maintain their innate oscillations. Our experiments demonstrate robust synchronization of spontaneous oscillations, with either 1:1 or multi-mode phase-locking. The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles. Coupling also led to an improved regularity of entrained oscillations, demonstrated by an increase in the quality factor. © 2015 Zhang et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Balas K.,California State University, Northridge | Balas K.,Los Angeles Mission College | Dumitrescu A.,University of Wisconsin - Milwaukee | Toth C.D.,California State University, Northridge | Toth C.D.,Tufts University
Leibniz International Proceedings in Informatics, LIPIcs | Year: 2016

For points p1, . . . , pn in the unit square [0, 1]2, an anchored rectangle packing consists of interior-disjoint axis-aligned empty rectangles r1, . . . , rn ⊆ [0, 1]2 such that point pi is a corner of the rectangle ri for i = 1, . . . , n (ri is anchored at pi). We show that for every set of n points in [0, 1]2, there is an anchored rectangle packing of area at least 7/12-O(1/n), and for every n ∈ ℕ, there are point sets for which the area of every anchored rectangle packing is at most 2/3. The maximum area of an anchored square packing is always at least 5/32 and sometimes at most 7/27. The above constructive lower bounds immediately yield constant-factor approximations, of 7/12 - ε for rectangles and 5/32 for squares, for computing anchored packings of maximum area in O(n log n) time. We prove that a simple greedy strategy achieves a 9/47-approximation for anchored square packings, and 1/3 for lower-left anchored square packings. Reductions to maximum weight independent set (MWIS) yield a QPTAS and a PTAS for anchored rectangle and square packings in nO(1/ε) and exp(poly(log(n/ε))) time, respectively. © Kevin Balas, Adrian Dumitrescu, and Csaba D. Tóth. Source

Balas K.,California State University, Northridge | Balas K.,Los Angeles Mission College | Toth C.D.,California State University, Northridge | Toth C.D.,Tufts University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

We consider packing axis-aligned rectangles r1, . . . , rn in the unit square [0, 1]2 such that a vertex of each rectangle ri is a given point pi (i.e., ri is anchored at pi); and explore the combinatorial structure of all locally maximal configurations. When the given points are lower-left corners of the rectangles, then the number of maximal packings is shown to be at most 2nCn, where Cn is the nth Catalan number. The number of maximal packings remains exponential in n when the points may be arbitrary corners of the rectangles. Our upper bounds are complemented with exponential lower bounds. © Springer International Publishing Switzerland 2015. Source

Waktola D.K.,Los Angeles Mission College
Applied Geography | Year: 2015

This study attempt to visualize the spatial patterns of selected academic attributes across college classroom space based on data from a map-embedded smart attendances and GIS visualizations. The academic attributes of 542 participants from Los Angeles Mission College (LAMC) in California were analyzed in a GIS platform. The spatial dynamics of student success revealed the distance decay effect on test scores, class participation, and class attendance. The visualization of class performance highlighted the spatial interdependence between seat location and academic attributes, which was validated by 145 sample students' perceived mental maps generated from the accompanying questionnaire survey. The replication of the visualization technique across different class sizes and courses could help educators identify seats for early intervention and micromanagement of classrooms. © 2015 Elsevier Ltd. Source

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