Virtual MET Institution : assessing the potentials and challenges of applying multi-user virtual environment in maritime education and training

The dissertation is a study to assess the potentials and challenges in the use of Multi-User Virtual Environment (MUVE) in Maritime Education and Training (MET) context. Virtual technology is growing at fast pace. The applications of MUVE are being utilized by numerous institutions across many educational professions. However, the area of utilizing MUVE in MET is still very limited. At the time being, it is indicated that there is possibility to take advantages of MUVE to create: (1) an enhance learning environment, (2) collaboration tools to support the distributed knowledge community, and (3) new modes of distance learning. METs are facing with several contemporary issues. There are necessities to foster the learning experience of future seafarers, to promote expertise exchange, and to continuously support its community of practice from distance. The investigation of MUVE’s characteristics and its applications suggests chances to tackle the such issues. Obviously, assessing the potentials and challenges of applying MUVE in MET become critical. The assessment tasks are conducted by examining the potentials that an institution can benefit as well as challenges that it would face. Then it is repositioned into MET contexts by taking into account the reality of MET’s culture and practices. The outcomes of the assessments indicate the affordance of MUVE for educational activities in MET institutions. Being aware of the limitations of the research itself, a number of recommendations are made concerning the need for further investigation in the subject

Building A Comprehensive Conceptual Framework for Material Selection in Terms of Sustainability in The Construction Preliminary Design Phase

Construction projects consume a massive amount of renewable and non-renewable resources and negatively affect sustainable development. The selection of materials is necessary to meet the demands of sustainability. The preliminary design phase is essential within construction project phases because the main requirements, budget, and master drawings are planned here. Also, the selection of primary materials is considered in this phase. However, the integration of material selection and sustainability in the preliminary design phase has been underestimated. This paper reviewed sustainability in the preliminary design phase and the importance of material selection in accordance with sustainability in this phase. By using current literature and tools like Leadership in Energy and Environmental Design (LEED) and Building Research Establishment Environmental Assessment Method (BREEAM), the paper establishes a conceptual framework including sub-aspects that relate to sustainable aspects (economy, environment, and society). The proposed sus-aspects, such as total cost, cost efficiency, budget management, and water efficiency, define the relevant activities that help select the most sustainable materials. The results can be applied as a guide to decision-makers and promote sustainability right from the preliminary design phase. Future studies may provide methods for each criterion and establish a detailed plan to apply this framework in practice

Applications of Spectrally-Resolved Photoluminescence in Silicon Photovoltaics

In broad terms, this thesis is devoted to measuring and interpreting the photoluminescence spectra emitted from different structures in crystalline silicon wafers and solar cells. Based on the knowledge accumulated, it also establishes a variety of applications of photoluminescence spectroscopy in silicon photovoltaics. The thesis may be divided into 3 main categories: band-to-band luminescence from wafers, deep-level luminescence from defects and impurities, and composite luminescence from different structures and layers in solar cells. First, this thesis utilizes band-to-band photoluminescence spectra emitted from planar silicon wafers to determine the values of the band-to-band absorption coefficient and the radiative recombination coefficient as a function of temperature with high precision. Parameterizations of these two coefficients are established to allow convenient calculations. Based on the newly established temperature data, the impacts of surface geometries and excess carrier profiles on luminescence spectra emitted from various silicon wafers are investigated via both modeling and experiments as a function of temperature. The results suggest that, the accuracy of many photoluminescence-based techniques, established mainly at room temperature in the literature, can be further improved by performing the measurements at higher temperatures due to the increasing impacts of surface reflectivities and excess carrier profiles on luminescence spectra with rising temperatures. These applications highlight the significance of the established data of the two coefficients for spectral fitting techniques. Next, the thesis investigates the deep-level luminescence from defects and impurities distributed around sub-grain boundaries in multicrystalline silicon wafers. The thesis shows that, the dislocations at sub-grain boundaries and the defects and impurities trapped around the dislocations emit separate luminescence peaks at low temperatures. The luminescence intensity of the trapped defects and impurities is found to be altered significantly after phosphorus gettering, whereas the dislocation luminescence is not changed throughout different solar cell processing steps. Also, the trapped defects and impurities are found to be preferentially distributed on one side of the sub-grain boundaries due to the asymmetric distribution of their luminescence intensity across the sub-grain boundaries. In addition, the thesis also demonstrates that the damage induced by laser doping is related to dislocations, since its deep-level luminescence spectrum has similar properties to those emitted from dislocations in multicrystalline silicon wafers. The interface between the laser-doped and un-doped regions is found to contain more damage than the laser-doped regions. Furthermore, the thesis reports a new photoluminescence-based method to separate the luminescence signatures from different layers and structures in a single silicon substrate, courtesy of the well-resolved luminescence peaks at low temperatures from different layers. In particular, the technique is applied to characterize the doping level of both locally-diffused and laser-doped regions on various silicon solar cells and cell precursors, utilizing band-gap narrowing effects in heavily-doped silicon. The results show that, the interface between the laser-doped and un-doped regions is much more heavily-doped that the doped regions. In addition, the technique is also applied to evaluate and the parasitic absorption of different surface passivation films on finished solar cells, due to the correlation between the sub band-gap luminescence intensity from these passivation films and the optical absorption in the films. The technique is contactless and nondestructive, requires minimal sample preparation, and provides micron-scale spatial resolutions. Finally, the thesis combines the advantages of spectrally-resolved photoluminescence (PLS) and photoluminescence excitation spectroscopy (PLE) to develop a PLS-PLE-combined technique for characterizing wafers and solar cells. In particular, the entire photoluminescence spectrum from a silicon wafer or solar cell is captured and monitored while the excitation energy is varied. This technique allows us to quantitatively evaluate both the doping level and the junction depth of various diffused silicon wafers, the defects induced by the post-diffusion thermal treatment at different depths below the wafer surface, and the enhanced diffusion at grain boundaries and sub-grain boundaries in multicrystalline silicon wafers. The results show that, the enhanced diffusion happens at both grain boundaries and sub-grain boundaries

Evaluation of water depth and wave propagation characteristics by using aerial image sensing and infrared laser scanning

東京海洋大学博士学位論文 2020年度(2020年9月) 応用環境システム学 課程博士 甲第573号指導教員: 池谷毅全文公表年月日: 2022-03-22東京海洋大学2020年

VFFINDER: A Graph-based Approach for Automated Silent Vulnerability-Fix Identification

The increasing reliance of software projects on third-party libraries has raised concerns about the security of these libraries due to hidden vulnerabilities. Managing these vulnerabilities is challenging due to the time gap between fixes and public disclosures. Moreover, a significant portion of open-source projects silently fix vulnerabilities without disclosure, impacting vulnerability management. Existing tools like OWASP heavily rely on public disclosures, hindering their effectiveness in detecting unknown vulnerabilities. To tackle this problem, automated identification of vulnerability-fixing commits has emerged. However, identifying silent vulnerability fixes remains challenging. This paper presents VFFINDER, a novel graph-based approach for automated silent vulnerability fix identification. VFFINDER captures structural changes using Abstract Syntax Trees (ASTs) and represents them in annotated ASTs. VFFINDER distinguishes vulnerability-fixing commits from non-fixing ones using attention-based graph neural network models to extract structural features. We conducted experiments to evaluate VFFINDER on a dataset of 36K+ fixing and non-fixing commits in 507 real-world C/C++ projects. Our results show that VFFINDER significantly improves the state-of-the-art methods by 39-83% in Precision, 19-148% in Recall, and 30-109% in F1. Especially, VFFINDER speeds up the silent fix identification process by up to 47% with the same review effort of 5% compared to the existing approaches.Comment: Accepted by IEEE KSE 202

Accurate Estimation without Calibration of the Complex Relative Permittivity of Multilayer Dielectric Material based on the Finite Integration Technique

In this paper, a simple and effective solution is proposed to accurately estimate the complex relative permittivity of individual layers and multilayers of dielectric material samples from the S-parameters measured by two waveguide cells having equal or different lengths filled with the same vacuum/empty material without having to calibrate before performing experiments. The measurement system is set up by modeling using the Computer Simulation Technology (CST) software. In the modeling, a single layer/multilayer material sample is placed in the X-band rectangular waveguide and it has two ports used for the electromagnetic wave supply and measurement of S-parameters. From the S-parameters measured, the complex relative permittivity of individual layers and the multilayers of the material samples are estimated by the proposed method. The known single-layer and multilayer materials such as Garlock, Bakelite, and Teflon have different dielectric constants and thicknesses. The results show that the complex relative permittivity of the samples matches the measured and calculated values of S-parameters in the frequency range of 8.2GHz to 12.4GHz

Grundlegende betrachtungen zur wirkung eines "inversen" spanungsverhältnisses als basis für die fräswerk-zeugkonstruktion

The demand for higher productivity and quality, flexibility as well as process safety are marking the development in the field of metal-cutting manufacturing process. Thereby the field of low vibration milling plays a special role. Therefore the development and design of modern milling tools is more and more often affected by novel machining strategies. The article deals with the development and design of a low vibration milling tool including the reversal of conventional chip- cross- section b/h > 1 to the "invers" ratio b/h < 1. For this the difference between the two cross sections will be analysed. The focus of the first experimental research is the determination of the effects of reversing the chip- cross- section on the cutting forces as well as chip formation and - forming. The influence of the tool side rake angle (γf) in milling with "inverse" chip- cross- section will be studied. The results gathered in the field of "inverse" chip- cross- ratio provides the base for formulation of design fundamentals and drafts of a novel milling tool with peeling function

Organisational Baseline Study: Overview report for Ma CSV, Vietnam (VN01)

According to the data provided by Yen Bai Statistics Department (YSD), the total area of Yen Bai about 668,628 ha, of which 87.5% (585,089 ha) are agricultural land. Most of the province’s agricultural lands are sloping. The province shares the common features of the North-western Vietnam: terrain is complicated and are strongly fragmented by mountain and stream systems; climate is tropical and with different climatic sub- regions. Over 70% of the population (over 70%) are agricultural. Yen Binh district locates in the south of Yen Bai province, with the total area of 77,262 ha, and is diverse and rich in natural resources. Having diverse agricultural production activities (including crop, livestock, aquaculture and forestry) and sharing the common features with the province, Ma village has been facing important challenges caused by natural resource degradation, environmental pollution and climate variability. On the other hand, there are also great potentials for this village to develop sustainable and climate smart livelihoods and agriculture. Ma village, Vinh Kien commune, Yen Binh district, Yen Bai province has therefore been selected to be a site for building Climate Smart Villages (CSV) under the CGIAR Program “Climate Change, Agriculture and Food Security (CCAFS). An organization baseline survey, was therefore conducted as part of the baseline effort for this village, which consists of three components – household survey, village study and organizational survey. The objectives of this organization baseline study (OBS) include: - Provide indicators to allow us to monitor changes in behaviours and practices of relevant local organizations over time; - Understand the current status of provision of information/services at the local level that informs farmers’ decision making about their livelihood strategies in response to climate change. To gather necessary information, we conducted survey of organizations of which activities covered a wide range in all the aspects: natural resources management, environment and climate change, agricultural production, agricultural product processing and input supplying. The list of these organization is presented in Table 1