Exploring Random Forest and Multilayer Perceptron for Container Throughput Forecasting: The Case of the Port of Douala, Cameroon

PENN COLLINS AWAH Graduate School of Korea Maritime & Ocean Universi 2021 국내석사

An accurate container throughput forecast is vital for any port. Since overall improvements in port performance and competitiveness can be derailed by port bottlenecks, ports need to find leverage to identify and prioritize measures to improve weak key performance indicators (KPI) to attain growth opportunities. Prior studies had modeled container throughput from socioeconomic and growth projection factors. This study aims to provide a practical method for forecasting the optimal container throughput a port can physically handle/attract given a certain level of terminal operation efficiency through random forest (RF) and multilayer perceptron (MLP) models. The study variables are derived from the port operations dimension and include ship turnaround time, vessel draft, container dwell time, berth productivity, container storage capacity, and customs declaration time. Evaluations are made based on the R-squared, NRMSE, MAE & MAPE. Model comparison is deduced with seven competing models in container throughput forecasting. The findings indicate that the RF model is a potential candidate for forecasting the engineering optimal throughput of the Douala port. Model interpretation is provided through feature importance and partial dependence plots. The findings from this study will help reduce uncertainty and provide leverage for port management to spot bottlenecks and engage in better port planning and development projects which will strengthen their international competitive advantage.

Native and nonnative English speaking teachers’ feedback on Korean college students’ English writing : teachers’ beliefs and practices, and students’ incorporation

Penn, Seo Hyun Hankuk University of Foreign Studies. Graduate Sch 2018 국내박사

This study investigated how teachers give feedback to Korean EFL student writing and how feedback influences students' revision. This research attempted to fill gaps in the literature by examining teacher feedback in six aspects: (1) what EFL teachers believe regarding teaching writing and giving feedback, (2) teachers’ feedback lengths, types and frequencies, (3) effects of teacher feedback on student revision, (4) students’ reasons for incorporating and ignoring teacher feedback, (5) student perception about teacher feedback and (6) the effects on students’ improved writing and grammar proficiency. This study collected data from 74 English teachers (38 NESTs and 36 NNESTs) to examine their teaching methods of writing, feedback beliefs and their self-reported feedback practice. Ten focus group teachers were chosen to investigate their feedback practice in the language classroom. To explore the effects of teacher feedback, the total of 121 student participants participated in the study. They were divided into four groups: three treatment groups (NEST group, NNEST group and both feedback group) and a control group. The findings indicated that both groups of teachers considered teaching English writing and giving feedback to EFL students an integral part of students’ writing and linguistic development. NESTs and NNESTs demonstrated comparable ways of giving feedback to student writing: eighty-eight percent of their feedback was corrective feedback while 12% consisted of teacher commentaries. While teachers were cautious in giving content feedback avoiding teacher appropriation, they marked every error they saw on their students’ writing. These teachers preferred to use direct corrective feedback (99%) than indirect. They also gave more sentence level comments than they did discourse level comments. The most salient differences emerged from the amounts of feedback they gave and the time spent on student writing. The findings of student incorporation and survey responses indicated that students appreciate teacher feedback and tried to incorporate teacher feedback into their revision as best they could. The students were able to incorporate corrective feedback in a higher degree (93%) than teacher commentaries (66%). When the students’ incorporation rates were compared, students were able to incorporate NEST feedback with higher degrees. The current research did not confirm the results from previous studies, of which, had said that the degree of revision was affected by the forms of the feedback. Rather the specificity of the feedback determined the success of the incorporation. While types of feedback were given interrogatively, declaratively and imperatively, the students’ incorporation rates varied. Another finding of the study is that Korean college students made the most frequent errors in the order of sentence structure, word choice, punctuation, articles, singular/plural, word form and pronouns. These are the areas in which Korean students need pedagogical help; especially from their English writing teachers to communicate more efficiently in writing. The current study results are encouraging for both NESTs and NNESTs. While researching the influence of teacher feedback, the treatment groups improved across the board based on the quantitative analysis of students’ pre- and post-tests results. Three treatment group students showed significant improvement of English writing proficiency and grammar accuracy (ps < .05) over the control group. The findings of this study confirmed the possible link between teacher feedback and student revision. Further, this study found that treatment group students showed preference toward certain types of feedback for what they were, not because it was given by an NEST or NNEST. In addition, the teacher’s status as native or nonnative did not have a significant affect between the two treatment groups. The current research evidenced that studying student errors through writing and rewriting exercises could benefit these EFL students in a way that promotes students’ linguistic awareness for English development. The results indicate that writing essays, receiving feedback and incorporating feedback are, in themselves, more important than is the status of the teacher whose feedback the students receive. Based on the results obtained in this study, various instructional insights and implications for EFL teachers were discussed in the areas of teaching and giving more effective feedback. The current study warrants the necessity of implementing teacher training for both NESTs and NNESTs. 본 연구의 목적은 원어민과 한국인 영어 교사들이 한국 대학생의 글에 어떻게 피드백을 주고, 그들의 피드백이 학생들의 글에 어떠한 영향을 미치는지를 알아보고자 하는 것이었다. 첫째 단계에서는 38명의 원어민 영어교사와 36명의 한국인 영어교사가 설문조사에 참여하였다. 두 번째 단계에서는 74명의 교사들 중 대학생을 가르치고 있는 교육수준과 전공이 일치하는 원어민과 한국인 교사들을 각 5명씩 선별하여, 실험 집단에 속하는 71명의 한국 대학생 영어 학습자들에게 피드백을 주도록 했다. 총 121명의 한국 대학교 1학년 영어 학습자들을 세 그룹으로 나누어 (원어민 교사로부터 피드백을 받은 그룹, 한국인 교사로부터 피드백 받은 그룹, 통제 그룹) 쓰기와 문법 선시험과 후시험에서의 변화, 그리고 그들의 이 두 교사들에 대한 인식을 살펴보았다. 위의 양적, 질적 자료 분석 결과, 첫째, 원어민 교사와 한국인 교사 모두 영어 쓰기를 한국인 학생들에게 가르치는 것과 학생들의 글에 피드백을 주는 것이 한국인 학생들의 쓰기와 문법 더 나아가 언어실력 향상에 필수적인 요소임을 인식하고 있다는 것을 발견했다. 본 연구에서 대부분의 교사들은 국적에 상관없이 모두 피드백에 대해 긍정적인 효과를 인식하고 이를 중요한 교육적인 전략으로 간주하고 있었다. 또한 세 명의 상중하 레벨의 학생들의 글에 준 피드백에도 나타났듯이 두 집단의 교사들 모두 피드백에 대한 유사한 개념을 가지고 있었는데, 두 집단의 교사들의 피드백은 내용에 대한 피드백보다는 문법에 대한 피드백이 주류를 이루고 있음을 발견하였다. 한편, 원어민과 한국인 교사들은 그들이 학생들의 글에 소비하는 시간에서 뚜렷한 차이를 보였으며, 원어민 교사들이 한국인 교사들에 비해 55%나 많은 피드백을 주었다. 두 집단의 교사들이 실제 영어 수업을 받고 있는 학생들에게 준 피드백 분석 결과, 교사들은 학생들의 글의 내용(13%)보다는 문법 오류(87%)에 집중하여 피드백을 주고 있는 것으로 밝혀졌다. 또한 영어교사들은 선택적으로 피드백을 특정한 오류를 선택하여 주는 것이 아니라, 학생들의 글에서 발견한 모든 오류에 피드백을 주고 있다는 것이 발견되었다. 또 다른 시사점은 다양한 방식의 문법 오류 피드백 방식이 있음에도 불구하고 본 연구에서는 두 집단의 교사들 모두 99%의 피드백이 직접적인 오류 피드백 방식을 사용하고 있다는 결과를 보여주었다. 따라서 교사들은 직접적인 오류 피드백 방식 외에도 다른 다양한 방법의 오류 피드백 방법과 장점을 교사 연수나 세미나를 통해 재교육을 받을 필요가 있음을 본 연구가 시사한다. 학생들의 피드백 활용률 분석 결과, 학생들은 내용에 관한 피드백의 활용률은 원어민교사의 피드백의 경우 76%, 한국인 교사의 경우 61%를 보였고, 문법 오류에 대한 피드백의 경우 원어민 교사의 피드백은 94%, 한국인 교사의 피드백에는 92%의 활용률을 보였다는 것이다. 본 연구에서는 선행연구의 결과와는 달리 한국인 학생들은 의문문으로 피드백이 주어졌다고 해서 학생들의 피드백 반영률이 영향을 주지 않고 오히려 피드백이 얼마나 자세히 무엇을 해야 할지를 알려주었을 때 그 차이를 보였다. 따라서 효과적인 교사의 피드백은 일반적이고 모호한 피드백이 아니라 실제로 어떻게 수정을 해야 하는지에 대한 단서를 제공하는 피드백으로, 이러한 피드백만이 학생들의 피드백 반영률을 높인다는 것을 발견하였다. 문법 오류에 대한 피드백의 경우, 본 연구의 학생 참여자들은 선행연구에서 보고된 반영률보다 훨씬 높은 반영률을 보여주었다. 선시험, 후시험 분석 결과, 원어민 교사와 한국인 교사의 차이 없이, 교사의 피드백을 한 학기 동안 받은 학생들의 실험 집단이 통제집단보다 후시험 성적이 통계적으로 유의미한 증가를 보였다. 따라서 이 연구는 교사의 피드백의 중요성을 다시 한 번 강조하며, 한국인 교사의 피드백을 받은 학생들이 원어민 교사의 학생들에 비해 숫자상으로 훨씬 적은 양의 피드백을 받았음에도 불구하고, 통제집단에 비해 영어 쓰기와 문법 실력의 향상 면에서 통계적으로 유의미한 차이를 보였다. 이는 본 연구의 피드백을 받고, 피드백을 공부하고 이를 반영하는 쓰기 활동 차제가 학생들의 쓰기 실력과 문법지식을 증가시키는데 중요한 역할을 한다는 것을 시사한다. 본 연구의 또 다른 시사점은 쓰기 교육 과정 개발자들의 교육 개발 과정에서 참고용으로 활용 될 수 있으며, 쓰기 수업을 구상하는 교육 현장에 있는 원어민과 한국인 교사에게도 도움이 될 수 있으리라 여겨진다.

Optimal Allocation of Power Distribution Network Automation Devices for Network Reliability Improvement

TICHAA JOHNSON PENN 한동대학교 국제개발협력대학원 2019 국내석사

As costs and consequences of manual power grid operations continue to offset reliability improvement efforts, a smarter approach to network operation is becoming a global trend. The benefits of an automated distribution system are multiple, from improved reliability and operation efficiency to safety improvement of network operators. Network automation, however. comes at a cost which explains the reluctance of several grid operators to adopt this technology. Partial network automation, that is, installing smart communicating switches at specific locations on the network rather than the entire network is a more palatable approach to tackle the high costs associated with total network automation which is actually unnecessary. And, in many cases, an inefficient approach to network automation results in diminishing returns. Knowing where to install the smart switches in a partially automated network and determining the optimal number to deploy are, therefore, key factors when deciding to go smart on network operation. In this study, an approach to solve this optimization problem based on the human-immune-system-inspired immune algorithm is developed, associating the problem and optimal solution in the same way how human body associate with pathogens and how optimal immune cells derive from the immune memory function. Implementing this method on the 15KV D14 Feeder of the Ngodi-Bakoko Distribution Substation in Cameroon yielded a 36% improvement in the Total System Cost upon partial optimization and a 13% improvement with respect to the heuristically derived partial automation scheme which would have been believed to be the optimal solution to automate D14 based on prior experience

Regulation of, by, and for Sex-lethal in Drosophila melanogaster

Penn, Jill Kristin Mellis Princeton University 2006 해외박사(DDOD)

Understanding how genes control sexual dimorphism is a fundamental problem in Developmental Biology. Over the last thirty years, geneticists and developmental biologists have uncovered a sex determination hierarchy for Drosophila melanogaster. It is now well-established that the initial choice of sexual identity is determined by the X chromosome to Autosome ratio which activates the transcription of Sex-lethal (Sxl) in females (XX) but not males (XY). Sxl expression is maintained in females throughout development via an autoregulatory alternative splicing event and is necessary for female differentiation. As Sxl also functions to prevent male-specific dosage compensation, loss of Sxl is female lethal. Since the maintenance of Sex-lethal expression is dependent upon regulated alternative splicing, mutations in general splicing regulators often lead to female-specific lethality. For example, mutations in fl(2)d lead to male-specific Sxl splicing and female lethality. Although fl(2)d is needed for the alternative splicing of other pre-mRNAs in Drosophila and its human homolog was isolated from functional spliceosomes, the precise function of fl(2)d is unknown. We attempted to determine the function of F1(2)d by characterizing its ability to interact with other well-defined splicing regulators. We found that Fl(2)d forms a stable complex with Sxl and the general splicing regulator Snf. Our experiments suggest that fl(2)d functions during the early stages of spliceosome assembly. During our analysis of fl(2)d, we serendipitously found that fl(2)d1 ovaries have egg chamber packaging defects. We next tried inducing Sxl- follicle cell clones and found that this also led to the same phenotype. Further analysis revealed that Sxl negatively regulates the Notch (N) signaling pathway in ovaries. In theory, however, Sxl could potentially regulate the N signaling pathway in tissues that are common to both sexes since both genes are expressed in common tissues. This immediately led us to ask, why would N be regulated differently in females compared to males? Using a series of genetic assays, we showed that the regulation of N by Sxl contributes to sexual dimorphism. Finally, we have evidence indicating that the interaction between Sxl and N might also be important in the female germline and in evolutionarily related species.

Cooperation and social choice: How foresight can induce fairness

Penn, Elizabeth Maggie California Institute of Technology 2003 해외박사(DDOD)

I present three models of dynamic agenda formation and policy selection, and demonstrate that in each, outcomes emerge which are in keeping with those predicted by cooperative solution concepts such as the von Neumann-Morgenstern stable set and the core. These outcomes are a consequence of players “thinking ahead,” or conditioning how they bargain on the notion that policies selected today should stand up to tomorrow's agenda. Players are induced into taking the payoffs of others into account when voting over and proposing policies, not because of a behavioral assumption such as altruism or inequality aversion, but because they know that the behavior of others in large part determines which policies are enacted in the future. In this sense, fairness is induced through the foresight of the players involved.

Promoter-specific restriction of MyoD binding and feed-forward regulation cooperate to produce a multi-staged transcriptional program during skeletal myogenesis

Penn, Bennett H University of Washington 2004 해외박사(DDOD)

The generation of multiple, highly specialized cell types in a regulated and reproducible manner is a challenge that all multicellular organisms face during development, yet the molecular mechanisms that pattern gene expression remain largely unknown. Coordinated gene expression in skeletal myogenesis is initiated by the muscle specific transcription factor MyoD. Here we show that an inducible MyoD-Estrogen Receptor chimeric protein, when expressed in mouse fibroblasts, generates a complex, multi-staged transcriptional response. MyoD recruitment in vivo is regulated in a promoter-specific manner, with immediate binding to early-stage genes, and binding delayed until the second day of differentiation at late-stage genes, suggesting that regulated MyoD recruitment is important in determining the timing of gene activation. In addition, MyoD regulates the expression of specific Mef2 isoforms and the activity of the p38 MAPK pathway. Subsequently, Mef2 and p38 cooperate with MyoD to regulate RNA Polymerase II recruitment and progression at late-stage genes, establishing a temporal pattern of gene expression. Thereby, MyoD directly activates genes expressed throughout the program of muscle differentiation and uses a feed-forward regulatory circuit to generate a multi-stage transcriptional program.

Thriving and Surviving: The Counternarratives of Black Women Teachers of English to Speakers of Other Languages

Penn, Carlotta ProQuest Dissertations & Theses The Ohio State Uni 2017 해외박사(DDOD)

Black women have a legacy of excellence as teachers, administrators, colleagues, and community members in the field of English language education. However, their expertise, perspectives, and voices continue to be underappreciated, under-researched, and therefore, too often unheard. Furthermore, given the ongoing impact of racism as a systemic force shaping U.S. society and the world, due to the global reach of U.S. culture and economy, Black women's personal and professional lives are necessarily affected. More specifically, Black women are regularly stereotyped and regarded as intellectually, professionally, and aesthetically inferior to their White and male counterparts. Therefore, this dissertation highlights the experiences of Black women teachers of English to speakers of other languages as counternarratives that can "shatter complacency, challenge the dominant discourse on race, and further the struggle for racial reform" (Solorzano and Yosso, 2002, p. 32). Researchers have published important work on the experiences of teachers of color who are Teachers of English to Speakers of Other Languages (TESOL), and of Black women in education, but there is scant literature specifically centering the experiences of Black women in TESOL. Therefore, this dissertation attends to the following research questions: How do race, gender, and racism impact the personal and professional lives of Black women educators in TESOL? How can their counternarratives enrich the existing literature that examines relationships among race, gender, and racism for women of color, generally, and Black women educators, specifically? My research is grounded in Critical Race Theory and Black Feminist Epistemology-intellectual traditions that definitively center Black and Black women ways of knowing and coming to know and understand the world, and that are unapologetically oriented toward racial equity and justice for all people. Critical race methodology guided my process of collecting, analyzing, and representing data. I conducted conversational interviews and Internet research during the data collection phase.

Depth-Dependent Chemical and Structural Profiling of Oxide Thin Films with Scanning Transmission Electron Microscopy

Penn, Aubrey Nance North Carolina State University ProQuest Dissertat 2021 해외박사(DDOD)

Complex oxide perovksites are among the most versatile materials from a chemical, structural, and applications perspective. The perovskite lattice can expand or contract to fit the structure of a substrate due to the flexible oxygen octahedral network, opening up epitaxial thin film perovskites to be widely studied. Novel phases of materials are formed when grown with thin film morphology, having tunable properties through interfacial engineering. Metal oxide heterostrucutres are additionally a testbed for fundamental studies on the chemical, atomic, and electronic reconstructions at complex heterointerfaces. The thin film systems of interest presented here are La1−xSrxMnO3 (LSMO), multilayered LSMO-(La1−xSrxCrO3, and SrRuO3 (SRO) grown on SrTiO3. Each of these systems are of interest for their attractive magnetic properties. LSMO is a colossal magnetoresistive ferromagnet that has been the focus of many thin film studies, but stymied in application due to the loss of magnetic character in ultra-thin films. Most recently, an investigation into multilayered LSMO-(La1−xSrxCrO3, or LSCO) heterostructures has uncovered new possibilities for ultra-thin LSMO. SRO, on the other hand, is an itinerant ferromagnet that has also been the subject of extensive study, having properties extremely sensitive to growth conditions and resultant film structure. Here, these films are investigated with scanning transmission electron microscopy (STEM) imaging in combination with electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy. The studies included here serve two purposes. First, to produce material results on with the STEM. In each case, advanced electron microscopy is used to characterize the films to determine structure-property relationships as a function of film depth to understand interfacial phenomena. Second, the materials are used to develop STEM image and EELS analysis techniques as well as isolate potential shortcomings of STEM analysis due to sample preparation effects. From a structural perspective, both LSMO and SRO thin films are model systems to develop analysis methods, having similar cationic, but different oxygen sublattice structure as well as depth-dependent structure that varies with proximity to the interface.

Viral and host determinants of HIV-1-mediated CD4+ T-cell infection and depletion in human lymphoid tissue: The role of viral coreceptor preference and CD4+ T-cell phenotype (Immune deficiency)

Penn, Michael L., Jr University of California, San Francisco 2000 해외박사(DDOD)

The central feature of human immunodeficiency virus type 1 (HIV-1) disease is the depletion of CD4<super>+</super> T-cells. The course of disease in HIV-1-infected individuals is determined by incompletely understood interactions between the virus and the host. The primary goal of this study was to examine how cellular entry, as determined by viral coreceptor preference, sets the stage for HIV-1-mediated depletion of CD4<super>+</super> T-cells. To accomplish this, we utilized a lymphoid histoculture system that recapitulated key aspects of HIV-1 infection <italic>in vivo</italic>. We inoculated human tonsil or spleen histocultures with a panel of paired HIV-1 strains that were isogenic except for envelope determinants that controlled coreceptor preference and measured the depletion of CD4<super>+</super> T-lymphocytes. We found that CXCR4-dependent HIV-1 strains depleted CD4<super>+</super> T-cells aggressively while CCR5-dependent strains depleted these cells only mildly. Furthermore, we determined that the ability to use additional coreceptors other than CCR5 and CXCR4 did not contribute significantly to increased HIV-1 pathogenicity in lymphoid tissue cultured <italic>ex vivo</italic>. Therefore, CCR5 and CXCR4 appear to be the dominant coreceptors influencing HIV-1-specific killing of T-cells in these tissues. A secondary goal of this study was to determine how host factors such as cellular activation, maturation, and proliferation impact HIV-1 replication and depletion of CD4<super>+</super> lymphocytes within human lymphoid tissues. Despite considerable <italic>in vitro</italic> evidence that these cellular attributes regulate HIV-1 replication, the endogenous microenvironment within lymphoid histocultures permitted <italic>de novo</italic> HIV-1 replication and depletion in essentially all CD4<super>+</super> T-cells regardless of phenotypic classification or proliferative status. Therefore, lymphoid histocultures support the infection and depletion of virtually all recognized T-cell subsets, including resting, naïve CD4<super>+</super> T-cells. Collectively, these studies exploited a human lymphoid histoculture model to identify and characterize major HIV-1- and host-specific factors that likely contribute significantly to the widespread collapse of the CD4<super> +</super> T-cell repertoire that characterizes the acquired immunodeficiency syndrome.

Another boom for Amazonia? Examining the socioeconomic and environmental implications of the new camu camu industry in Peru (Myrciaria dubia)

Penn, James W., Jr University of Florida 2004 해외박사(DDOD)

This study examines the socioeconomic and environmental implications of the new camu camu industry in Peru. Camu camu (Myrciaria dubia ) is a small tree native to wetlands of the Amazon basin. It is especially abundant in Peruvian Amazonia. The high vitamin-C content of the fruit has generated interest in exporting camu camu products from Amazonia to more-developed countries. The government of Peru has been actively promoting this new extractive industry, as well as the planting of camu-camu in rural areas. Non-governmental development organizations and private industry are now actively involved with camu camu projects and enterprises. In Peru, enthusiasm for this native species is high, because camu camu is expected to provide a much-needed and sustainable economic boost for the region. However, many questions about the environmental implications and socioeconomic impacts of the camu camu export industry need to be answered in order to understand its ecological and economic viability, and its effects on business and in rural communities. Findings indicate that camu camu has provided significantly more income to rural residents than is provided by the traditional boom and bust economies of Amazonia. Households who adopted camu camu as a new crop in their floodplain agroforestry systems farmed significantly more floodplain land than non-adopters, and were especially adept at experimenting with new innovations. Lack of agricultural credit is a major constraint to adopting camu camu as a new crop in Peru. Geographic isolation and the location of processing facilities in relation to fruit harvests present major obstacles to the economic viability of the new industry. Camu camu was found to be cultivated with a higher diversity of annual crops than is typical in floodplain fields of the region. Extraction of camu camu fruits from the wild does not appear to have a negative environmental impact, at least in the initial years of the industry. This non-timber forest product in the process of domestication can support a viable industry in the Peruvian Amazon, if agricultural extension methods and marketing channels are improved.