Shaking Table Tests on Seismic Deformation of Composite Breakwaters

A series of shaking table tests were conducted on composite breakwater systems under 30g centrifugal conditions. The emphasis was placed on investigating the mechanisms of seismic settlement of foundation ground, in particular of the contribution from the dispersion of mound rubble into the foundation soil. In-flight visual observation of the deformation process by a high-speed CCD camera showed the significance of cumulative vertical compression of foundation soils under cyclic loading. Pre- and post-shaking comparisons of weight of the rubble mound revealed that dispersion into the soil had occurred and contributed to caisson settlement

Disclosure of suicidal drivers on social media: a natural language processing and thematic analysis approach

It is common for people to search for health information on the internet, share their health issues through social media, and ask for advice from people in online communities. Some people reported feeling more comfortable sharing their psychological stress online and anonymously asking for advice from people. As such, people disclose not only their suicide risk but also their suicidal risk-associated drivers (e.g., suicide ideation, relational stress, financial crisis). This study aims to identify suicidal drivers from narratives extracted from social media, synthesize findings and suicide theories, and provide insights into future suicide prevention policies and practices. This research gathered and analyzed 128,587 posts written by 76,547 people worldwide. The posts were written in English from January 2021 to December 2022 on the r/SuicideWatch of Reddit. Natural Language Processing and topic modeling, specifically Latent Dirichlet Allocation (LDA), were used to identify clusters of posts based on similarities and differences between posts. Thematic analysis was used to identify suicidal drivers across clusters of posts. The web crawler developed by Brandwatch was used in data collection, and Python was used for all analyses.  Six theme clusters of posts were identified. The first theme was Disclosure of Repetitive Suicide Ideation (i.e., “I want to die. I want to die, I want to die…(repeated)”), and 36.4% of posts had this theme. The second theme was Disclosure of Relational Stress (i.e., “I don’t have any friends”), and 31.9% of posts had this theme. The third theme was Disclosure of Suicide Attempts and Negative Healthcare Experiences (i.e., “I’ve had a suicide attempt before”, “The nurses ignored me”), and 9.9% of posts had this theme. The fourth theme was Disclosure of Abuse (i.e., “He would beat me black and blue”), and 8.8% of posts had this theme. The fifth theme was Disclosure of Contextual Stress, including finance and legal matters (i.e., “every moment was a living fear of the debt collector knocking on the door”), and 7.2% of posts had this theme. The last theme was Philosophical and Informative Discussions around suicide (i.e., “After death, the physical begins to deteriorate and life/energy is simply moved to another being”), and 5.8% of posts had this theme. Understanding different suicidal drivers is an essential component in designing individualized intervention plans for people at suicide risk. The current research identified the idiosyncrasies in the suicide drivers people talked about when disclosing their suicidality. Furthermore, the findings from this study’s data-inspired and exploratory approach provided additional evidence supporting existing suicide theories and frameworks. This research has the potential to lay the groundwork for designing suicide intervention strategies that target individuals’ self-disclosures of their struggles online

FiFo: Fishbone Forwarding in Massive IoT Networks

Massive Internet of Things (IoT) networks have a wide range of applications, including but not limited to the rapid delivery of emergency and disaster messages. Although various benchmark algorithms have been developed to date for message delivery in such applications, they pose several practical challenges such as insufficient network coverage and/or highly redundant transmissions to expand the coverage area, resulting in considerable energy consumption for each IoT device. To overcome this problem, we first characterize a new performance metric, forwarding efficiency, which is defined as the ratio of the coverage probability to the average number of transmissions per device, to evaluate the data dissemination performance more appropriately. Then, we propose a novel and effective forwarding method, fishbone forwarding (FiFo), which aims to improve the forwarding efficiency with acceptable computational complexity. Our FiFo method completes two tasks: 1) it clusters devices based on the unweighted pair group method with the arithmetic average; and 2) it creates the main axis and sub axes of each cluster using both the expectation-maximization algorithm for the Gaussian mixture model and principal component analysis. We demonstrate the superiority of FiFo by using a real-world dataset. Through intensive and comprehensive simulations, we show that the proposed FiFo method outperforms benchmark algorithms in terms of the forwarding efficiency.Comment: 13 pages, 16 figures, 5 tables; to appear in the IEEE Internet of Things Journal (Please cite our journal version that will appear in an upcoming issue.

Follow spam detection based on Cascaded Social Information

In the last decade we have witnessed the explosive growth of online social networking services (SNSs) such as Facebook, Twitter, RenRen and LinkedIn. While SNSs provide diverse benefits for example, forstering inter-personal relationships, community formations and news propagation, they also attracted uninvited nuiance. Spammers abuse SNSs as vehicles to spread spams rapidly and widely. Spams, unsolicited or inappropriate messages, significantly impair the credibility and reliability of services. Therefore, detecting spammers has become an urgent and critical issue in SNSs. This paper deals with Follow spam in Twitter. Instead of spreading annoying messages to the public, a spammer follows (subscribes to) legitimate users, and followed a legitimate user. Based on the assumption that the online relationships of spammers are different from those of legitimate users, we proposed classification schemes that detect follow spammers. Particularly, we focused on cascaded social relations and devised two schemes, TSP-Filtering and SS-Filtering, each of which utilizes Triad Significance Profile (TSP) and Social status (SS) in a two-hop subnetwork centered at each other. We also propose an emsemble technique, Cascaded-Filtering, that combine both TSP and SS properties. Our experiments on real Twitter datasets demonstrated that the proposed three approaches are very practical. The proposed schemes are scalable because instead of analyzing the whole network, they inspect user-centered two hop social networks. Our performance study showed that proposed methods yield significantly better performance than prior scheme in terms of true positives and false positives.OAIID:RECH_ACHV_DSTSH_NO:T201620357RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A001118CITE_RATE:3.364FILENAME:Follow spam detection based on cascaded social information.pdfDEPT_NM:컴퓨터공학부EMAIL:[email protected]_YN:YFILEURL:https://srnd.snu.ac.kr/eXrepEIR/fws/file/be43ae94-4659-467d-bc0f-17dc45d3e775/linkCONFIRM:

Health and healthcare in North Korea: a retrospective study among defectors.

BACKGROUND: To gain insights into the socio-economic and political determinants of ill health and access to healthcare in North Korea. METHODS: A retrospective survey using respondent-driven sampling conducted in 2014-15 among 383 North Korean refugees newly resettling in South Korea, asking about experiences of illness and utilization of healthcare while in North Korea, analyzed according to measures of political, economic and human rights indicators. RESULTS: Although the Public Health Act claims that North Korea provides the comprehensive free care system, respondents reported high levels of unmet need and, among those obtaining care, widespread informal expenditure. Of the respondents, 55.1% (95%CI, 47.7-63.7%) had received healthcare for the most recent illness episode. High informal costs (53.8%, 95%CI, 45.1-60.8%) and a lack of medicines (39.5%, 95%CI, 33.3-47.1%) were reported as major healthcare barriers resulting in extensive self-medication with narcotic analgesics (53.7%, 95%CI, 45.7-61.2%). In multivariate logistic regressions, party membership was associated with better access to healthcare (Adjusted OR (AOR) = 2.34, 95%CI, 1.31-4.18), but household income (AOR = 0.40, 95%CI 0.21-0.78) and informal market activity (AOR = 0.29, 95%CIs 0.15-0.50) with reduced access. Respondents who could not enjoy political and economic rights were substantially more likely to report illness and extremely reduced access to care, even with life-threatening conditions. CONCLUSIONS: There are large disparities in health and access to healthcare in North Korea, associated with political and economic inequalities. The scope to use these findings to bring about change is limited but they can inform international agencies and humanitarian organizations working in this unique setting

Positional vertigo afterwards maxillary dental implant surgery with bone regeneration

Benign paroxysmal positional vertigo (BPPV) is the most common form of vertigo. It is caused by loose otoconia from the utricle which, in certain positions, displaced the cupula of the posterior semicircular canal. BPPV most often is a result of aging. It also can occur after a blow to the head. Less common causes include a prolonged positioning on the back (supine) during some surgical procedures. Additionally one can include in this ethiopathogenesis the positioning required during the maxillary dental implant surgery with bone regeneration related to a forced head positioning and inner ear trauma induced by dental turbine noise working in the maxillary bone. Two cases of patients who suffered BPPV after undergoing maxillary dental implant with bone regeneration procedures are reported. Diagnosis and treatment are also described

Development of Parametric Trend Life Cycle Assessment for marine SOx reduction scrubber systems

In response to the impending international maritime regulation, MARPOL Annex VI Reg. 14, to curb sulphur oxides (SOx) arising from shipping activities, this paper aimed to evaluate the environmental impacts of the entire life cycle of three different SOx reduction scrubber systems: (1) ‘wet open-loop’, (2) ‘wet closed-loop’, and (3) ‘wet hybrid’. To achieve this goal, the paper developed ‘the Parametric Trend Life Cycle Assessment (PT-LCA)’ which was introduced to proceed the extensive analysis for a number of case ship studies and quantify various emissions, such as greenhouse gases (GHG), sulphur oxides (SOx), nitrogen oxides (NOx), associated with the proposed systems from cradle to grave. A case study designed with the database consisting of 1,565 ocean-going Ro-Ro vessels based on Lloyd’s Register has revealed that, in terms of Global Warming Potential (GWP) and Acidification Potential (AP), closed-loop scrubbers were proven more environmentally friendly than open-loop scrubbers, but the opposite was true for Eutrophication Potential (EP). By identifying specific trends in scrubber systems in relation to various input parameters, the assessment contributed to improving environmental sustainability, as well as the total estimated amount of numerical environmental impacts that the scrubber systems have for the international fleets. The proposed framework enabled us not only to evaluate the different emission levels of systems applied to various ships but also to obtain the general trends of emission levels over ship parameters, which were expressed as formulae. The novelty of this paper can be placed on the provision of an insight into the optimal selection of scrubber systems depending on ship characteristics. It could also offer an insight into the improvement of current environmental regulations and guidelines by means of PT-LCA