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Open Access Publications from the University of California

Scholarly Works (68 results)

  • Article
Capstone Projects (2016)
The biological feasibility of integrating Mercenaria mercenaria clams onto an existing shrimp farm was investigated. Effects on water were measured through a tank trial involving 2 treatments of shrimp stocked with different densities of clams (50/m2; 100/m2), and a shrimp-only control treatment. Significantly lower (p < 0.05) levels of total suspended solids (TSS) and organic suspended solids (OSS) were found in both clam treatments compared to the control treatment. Total ammonium nitrogen (TAN) was found to be significantly higher (p < 0.05) in the 50 clams/m2 treatment than the 100 clams/m2 and control treatments. Shrimp growth was not significantly different among treatments (p > 0.5). 60,400 M. mercenaria clams were stocked in a semi-intensive (50 shrimp/m2) P. vannamei shrimp pond in Hawaii, USA for 104 days to measure clam growth and survival. Average clam growth was 10.3±3.1 x 8.3±2.8, and total weight increased from 405.85lbs to 974.05lbs over 104 days of integrated pond production. Estimated clam survival averaged 86% from stocking to harvest. The findings of this study suggest high potential for M. mercenaria clams as a candidate for integrated pond production with P. vannamei shrimp
    Cover page: Integrated Aquaculture of Shrimp and Clams: A Study of Economic Feasibility and Environmental Effect
      LBL Publications (1977)
        Cover page: SEPARATION AND CHARACTERIZATION OF SUBCLASSES OF HUMAN SERUM HIGH DENSITY LIPOPROTEINS AND THEIR DETERMINATION IN A CALIFORNIA POPULATION SAMPLE
        • Article
        • Peer Reviewed
        Cliodynamics, Volume 1, Issue 1 (2010)

        Warfare is commonly viewed as a driving force of the process of aggregation of initially independent villages into larger and more complex political units that started several thousand years ago and quickly lead to the appearance of chiefdoms, states, and empires. Here we build on extensions and generalizations of Carneiro’s (1970) argument to develop a spatially explicit agent-based model of the emergence of early complex societies via warfare. In our model polities are represented as hierarchically structured networks of villages whose size, power, and complexity change as a result of conquest, secession, internal reorganization (via promotion and linearization), and resource dynamics. A general prediction of our model is continuous stochastic cycling in which the growth of individual polities in size, wealth/power, and complexity is interrupted by their quick collapse. The model dynamics are mostly controlled by two parameters, one of which scales the relative advantage of wealthier polities in between and within-polity conflicts, and the other is the chief’s expected time in power. Our results demonstrate that the stability of large and complex polities is strongly promoted if the outcomes of the conflicts are mostly determined by the polities’ wealth/power, if there exist well-defined and accepted means of succession, and if control mechanisms are internally specialized.

          Cover page: Cycling in the Complexity of Early Societies
          • Article
          Working Paper Series (1998)
          Transportation professionals have always been interested in how travelers respond to different transportation options. A new application of congestion pricing offers the opportunity to extend such research to situations where travelers face a priced alternative. Travelers along State Route 91 (SR 91) in Southern California can now pay a time-varying fee in order to travel on a set of essentially congestion-free "Express Lanes" located in the median of a very congested preexisting freeway. For this study, we conduct a mail survey of such travelers to learn how they decide to use the free lanes or the toll lanes. We use the data to estimate route choice models and models that incorporate various types of real-time information about accidents, traffic conditions, and price levels into the route choice decision. This study provides new information about the acceptance of congestion pricing, the use of real-time information in making dynamic travel decisions, and individual travelers' interests in forming carpools.
            Cover page: Benefits, Acceptance, and Marketability of Value-Priced Services: California's Route 91 Express Lanes
            • Article
            • Peer Reviewed
            UC Berkeley Previously Published Works (2009)
            Middleware systems for volunteer computing convert a set of computers that is large and diverse (in terms of hardware, software, availability, reliability, and trustworthiness) into a unified computing resource. This involves a number of scheduling policies and parameters, which have a large impact on the throughput and other performance metrics. How can we study and refine these policies? Experimentation in the context of a working project is problematic, and it is difficult to accurately model complex middleware in a conventional simulator. Instead, we use an approach in which the policies being studied are “emulated”, using parts of the actual middleware. In this paper we describe EmBOINC, an emulator based on the BOINC middleware system. EmBOINC simulates a population of volunteered clients (including heterogeneity, churn, availability, and reliability) and emulates the BOINC server components. After describing the design of EmBOINC and its validation, we present three case studies in which the impact of different scheduling policies are quantified in terms of throughput, latency, and starvation metrics.
              Cover page: Performance Prediction and Analysis of BOINC Projects: An Empirical Study with EmBOINC
              • Article
              • Peer Reviewed
              Technical Reports (2007)
              Few Internet security issues have attained the universal public recognition or contempt of unsolicited bulk email -- SPAM. The engine that drives this enormous activity is not spam itself -- which is simply a means to an end -- but the various money-making ``scams'' (legal or illegal) that extract value from Internet users. In this paper, we focus on the Internet infrastructure used to host and support such scams. Unlike mail-relays or bots, scam infrastructure is directly implicated in the spam profit cycle and thus considerably rarer and more valuable. Our goal is to measure and analyze this scam infrastructure to better understand the dynamics and business pressures exerted on spammers. To identify scam infrastructure, we employ an opportunistic technique called spamscatter. The underlying principal is that each scam is, by necessity, identified in the link structure of associated spams. To this end, we have built a system that mines email, identifies URLs in real time and follows such links to their eventual destination server. We further identify individual scams by clustering scam servers whose rendered Web pages are graphically similar using a technique called image shingling. Using the spamscatter technique on a large real-time spam feed (roughly 150,000 per day) we identify and analyze over 2,000 distinct scams hosted across more than 7,000 distinct servers.

              Pre-2018 CSE ID: CS2007-0887

                Cover page: Spamscatter: Characterizing Internet Scam Hosting Infrastructure
                • Article
                • Peer Reviewed
                Proceedings of the Annual Meeting of the Cognitive Science Society, Volume 34 (2012)
                  Cover page: The effect of metabolic loading on statistical learning
                  • Article
                  • Peer Reviewed
                  UC Irvine Previously Published Works (1996)
                  Previously published results suggest that the strength of the SW Indian Monsoon can vary significantly on century- to millenium time scales, an observation that has important implications for assessments of future climate and hydrologic change over densely populated portions of Asia. We present new, welldated, multi-proxy records of past monsoon variation from three separate Arabian Sea sediment cores that span the last glacial maximum to late-Holocene. To a large extent, these records confirm earlier published suggestions that the monsoon strengthened in a series of abrupt events over the last deglaciation. However, our data provide a somewhat refined picture of when these events took place, and suggest the primacy of two abrupt increases in monsoon intensity, one between 13 and 12.5 ka, and the other between 10 and 9.5 ka. This conclusion is supported by the comparisons between our new marine data and published paleoclimatic records throughout the African-Asian monsoon region. The comparison of data sets further supports the assertion that maximum monsoon intensity lagged peak insolation forcing by about 3000 years, and extended from about 9.5 to 5.5 ka. The episodes of rapid monsoon intensification coincided with major shifts in North Atlantic-European surface temperatures and ice-sheet extent. This coincidence, coupled with new climate model experiments, suggests that the large land-sea thermal gradient needed to drive strong monsoons developed only after glacial conditions upstream of, and on, the Tibetan Plateau receded (cold North Atlantic sea-surface temperatures, European ice-sheets, and extensive Asian snow cover). It is likely that abrupt changes in seasonal soil hydrology were as important to past monsoon forcing as were abrupt snow-related changes in regional albedo. Our analysis suggests that the monsoon responded more linearly to insolation forcing after the disappearance of glacial boundary conditions, decreasing gradually after about 6 ka. Our data also support the possibility that significant century-scale decreases in monsoon intensity took place during the early to mid-Holocene period of enhanced monsoon strength, further highlighting the need to understand paleomonsoon dynamics before accurate assessments of future monsoon strength can be made.
                    Cover page: The southwest Indian Monsoon over the last 18 000 yearsCreative Commons 'BY' version 4.0 license
                    • Article
                    • Peer Reviewed
                    UC Berkeley Previously Published Works (2009)
                    Internet based volunteer computing projects such as SETI@home are currently restricted to performing coarse grained, embarrassingly parallel master-worker style tasks. This is partly due to the “pull” nature of task distribution in volunteer computing environments, where workers request tasks from the master rather than the master assigning tasks to arbitrary workers. In this paper we propose algorithms for computing batches of medium grained tasks with deadlines in pull-style volunteer computing environments. We develop models of unreliable workers based on analysis of trace data from an actual volunteer computing project. These models are used to develop algorithms for task distribution in volunteer computing systems with a high probability of meeting batch deadlines. We develop algorithms for perfectly reliable workers, computation-reliable workers and unreliable workers. Finally, we demonstrate the effectiveness of the algorithms through simulations using traces from actual volunteer computing environments.
                      Cover page: Computing Low Latency Batches with Unreliable Workers in Volunteer Computing Environments
                      • Thesis
                      • Peer Reviewed
                      UC Berkeley Electronic Theses and Dissertations (2016)

                      As the amount of data collected in our world increases, reliable compression algorithms are needed when datasets become too large for practical analysis, when significant noise is present in the data, or when the strongest signals in the data are needed. In this work, two data compression algorithms are presented. The main result is a low-rank approximation algorithm (a type of compression algorithm) that uses modern techniques in randomization to repurpose a classic algorithm in the field of linear algebra called the LU decomposition to perform data compression. The resulting algorithm is called Spectrum-Revealing LU (SRLU).

                      Both rigorous theory and numeric experiments demonstrate the effectiveness of SRLU. The theoretical work presented also develops a framework with which other low-rank approximation algorithms can be analyzed. As the name implies, Spectrum-Revealing LU seeks to capture the entire spectrum of the data (i.e. to capture all signals present in the data).

                      A second compression algorithm is also introduced, which seeks to compression graphs. Called a sparsification algorithm, this algorithm can accept a weighted or unweighted graph and produce an approximation without changing the weights (or introducing weights in the case of an unweighted graph). Theoretical results provide a bound on the quality of the results, and a numeric example is also explored.

                        Cover page: Reliable and Efficient Algorithms for Spectrum-Revealing Low-Rank Data Analysis
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