• Title/Summary/Keyword: recommendations guidelines

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Resolving the 'Gray sheep' Problem Using Social Network Analysis (SNA) in Collaborative Filtering (CF) Recommender Systems (소셜 네트워크 분석 기법을 활용한 협업필터링의 특이취향 사용자(Gray Sheep) 문제 해결)

  • Kim, Minsung;Im, Il
    • Journal of Intelligence and Information Systems
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    • v.20 no.2
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    • pp.137-148
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    • 2014
  • Recommender system has become one of the most important technologies in e-commerce in these days. The ultimate reason to shop online, for many consumers, is to reduce the efforts for information search and purchase. Recommender system is a key technology to serve these needs. Many of the past studies about recommender systems have been devoted to developing and improving recommendation algorithms and collaborative filtering (CF) is known to be the most successful one. Despite its success, however, CF has several shortcomings such as cold-start, sparsity, gray sheep problems. In order to be able to generate recommendations, ordinary CF algorithms require evaluations or preference information directly from users. For new users who do not have any evaluations or preference information, therefore, CF cannot come up with recommendations (Cold-star problem). As the numbers of products and customers increase, the scale of the data increases exponentially and most of the data cells are empty. This sparse dataset makes computation for recommendation extremely hard (Sparsity problem). Since CF is based on the assumption that there are groups of users sharing common preferences or tastes, CF becomes inaccurate if there are many users with rare and unique tastes (Gray sheep problem). This study proposes a new algorithm that utilizes Social Network Analysis (SNA) techniques to resolve the gray sheep problem. We utilize 'degree centrality' in SNA to identify users with unique preferences (gray sheep). Degree centrality in SNA refers to the number of direct links to and from a node. In a network of users who are connected through common preferences or tastes, those with unique tastes have fewer links to other users (nodes) and they are isolated from other users. Therefore, gray sheep can be identified by calculating degree centrality of each node. We divide the dataset into two, gray sheep and others, based on the degree centrality of the users. Then, different similarity measures and recommendation methods are applied to these two datasets. More detail algorithm is as follows: Step 1: Convert the initial data which is a two-mode network (user to item) into an one-mode network (user to user). Step 2: Calculate degree centrality of each node and separate those nodes having degree centrality values lower than the pre-set threshold. The threshold value is determined by simulations such that the accuracy of CF for the remaining dataset is maximized. Step 3: Ordinary CF algorithm is applied to the remaining dataset. Step 4: Since the separated dataset consist of users with unique tastes, an ordinary CF algorithm cannot generate recommendations for them. A 'popular item' method is used to generate recommendations for these users. The F measures of the two datasets are weighted by the numbers of nodes and summed to be used as the final performance metric. In order to test performance improvement by this new algorithm, an empirical study was conducted using a publically available dataset - the MovieLens data by GroupLens research team. We used 100,000 evaluations by 943 users on 1,682 movies. The proposed algorithm was compared with an ordinary CF algorithm utilizing 'Best-N-neighbors' and 'Cosine' similarity method. The empirical results show that F measure was improved about 11% on average when the proposed algorithm was used

    . Past studies to improve CF performance typically used additional information other than users' evaluations such as demographic data. Some studies applied SNA techniques as a new similarity metric. This study is novel in that it used SNA to separate dataset. This study shows that performance of CF can be improved, without any additional information, when SNA techniques are used as proposed. This study has several theoretical and practical implications. This study empirically shows that the characteristics of dataset can affect the performance of CF recommender systems. This helps researchers understand factors affecting performance of CF. This study also opens a door for future studies in the area of applying SNA to CF to analyze characteristics of dataset. In practice, this study provides guidelines to improve performance of CF recommender systems with a simple modification.

  • Survey of Current Status of Quality Control of Gamma Cameras in Republic of Korea (감마카메라 정도관리 실태 조사)

    • Choe, Jae-Gol;Joh, Cheol-Woo
      • Nuclear Medicine and Molecular Imaging
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      • v.42 no.4
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      • pp.314-322
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      • 2008
    • Purpose: It is widely recognized that good quality control (QC) program is essential for adequate imaging diagnosis using gamma camera. The purpose of this study is to survey the current status of QC of gamma cameras in Republic of Korea for implementing appropriate nationwide quality control guidelines and programs. Methods: A collection of data is done for personnel, equipment and appropriateness of each nuclear medicine imaging laboratory's quality control practice. This survey is done by collection of formatted questionnaire by mails, emails or interviews. We also reviewed the current recommendations concerning quality assurance by international societies. Results: This survey revealed that practice of quality control is irregular and not satisfactory. The irregularity of the QC practice seems due partly to the lack of trained personnel, equipment, budget, time and hand-on guidelines. Conclusion: The implementation of QC program may cause additional burden to the hospitals, patients and nuclear medicine laboratories. However, the benefit of a good QC program is obvious that the hospitals can provide good quality nuclear medicine imaging studies to the patients. It is important to use least cumbersome QC protocol, to educate the nuclear medicine and hospital administrative personnel concerning QC, and to establish national QC guidelines to help each individual nuclear medicine laboratory.

    주사용 요오드화 조영제 및 MRI용 가돌리늄 조영제 유해 반응에 대한 한국 임상진료지침: 개정된 임상적 합의 및 권고안(2022년 제3판)

    • Se Won Oh;So Young Park;Hwan Seok Yong;Young Hun Choi;Min Jae Cha;Tae Bum Kim;Ji Hyang Lee;Sae Hoon Kim;Jae Hyun Lee;Gyu Young Hur;Jae Yeon Hwang;Sejoong Kim;Hyo Sang Kim;Ji Young Ryu;Miyoung Choi;Chi-Hoon Choi
      • Journal of the Korean Society of Radiology
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      • v.83 no.2
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      • pp.254-264
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      • 2022
    • The Korean Society of Radiology and Medical Guidelines Committee amended the existing 2016 guidelines to publish the "Korean Clinical Practice Guidelines for Adverse Reactions to Iodide Contrast for Injection and Gadolinium Contrast for MRI: The Revised Clinical Consensus and Recommendations (2022 Third Edition)." Expert members recommended and approved by the Korean Society of Radiology, the Korean Academy of Asthma, Allergy and Clinical Immunology, and the Korean Nephrology Society participated together. According to the expert consensus or systematic literature review, the description of the autoinjector and connection line for the infection control while using contrast medium, the acute adverse reaction, and renal toxicity to iodized contrast medium were modified and added. We would like to introduce the revised contents.

    Extracorporeal Membrane Oxygenation for Coronavirus Disease 2019: Expert Recommendations from The Korean Society for Thoracic and Cardiovascular Surgery

    • Jeong, In Seok;Kim, Woong-Han;Baek, Jong Hyun;Choi, Chang-Hyu;Choi, Chang Woo;Chung, Euy Suk;Jang, Jae Seok;Jang, Woo Sung;Jung, Hanna;Jung, Jae-Seung;Kang, Pil Je;Kim, Dong Jung;Kim, Do Wan;Kim, Hyoung Soo;Kim, Jae Bum;Kim, Woo-Shik;Kim, Young Sam;Kwak, Jae Gun;Lee, Haeyoung;Lee, Seok In;Lim, Jae Woong;Oh, Se Jin;Oh, Tak-Hyuck;Park, Chun Soo;Ryu, Kyoung Min;Shim, Man-Shik;Son, Joohyung;Son, Kuk Hui;Song, Seunghwan;The Korean Society for Thoracic and Cardiovascular Surgery COVID-19 ECMO Task Force Team
      • Journal of Chest Surgery
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      • v.54 no.1
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      • pp.2-8
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      • 2021
    • Since the first reported case of coronavirus disease 2019 (COVID-19) in December 2019, the numbers of confirmed cases and deaths have continued to increase exponentially despite multi-factorial efforts. Although various attempts have been made to improve the level of evidence for extracorporeal membrane oxygenation (ECMO) treatment over the past 10 years, most experts still hesitate to take an active position on whether to apply ECMO in COVID-19 patients. Several ECMO management guidelines have been published recently, but they reflect some important differences from the Korean medical system and aspects of real-world medical practice in Korea. We aimed to find evidence on the efficacy of ECMO for COVID-19 patients by reviewing the published literature and to propose expert recommendations by analyzing the Korean COVID-19 ECMO registry data.

    Factor Analysis for Exploratory Research in the Distribution Science Field (유통과학분야에서 탐색적 연구를 위한 요인분석)

    • Yim, Myung-Seong
      • Journal of Distribution Science
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      • v.13 no.9
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      • pp.103-112
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      • 2015
    • Purpose - This paper aims to provide a step-by-step approach to factor analytic procedures, such as principal component analysis (PCA) and exploratory factor analysis (EFA), and to offer a guideline for factor analysis. Authors have argued that the results of PCA and EFA are substantially similar. Additionally, they assert that PCA is a more appropriate technique for factor analysis because PCA produces easily interpreted results that are likely to be the basis of better decisions. For these reasons, many researchers have used PCA as a technique instead of EFA. However, these techniques are clearly different. PCA should be used for data reduction. On the other hand, EFA has been tailored to identify any underlying factor structure, a set of measured variables that cause the manifest variables to covary. Thus, it is needed for a guideline and for procedures to use in factor analysis. To date, however, these two techniques have been indiscriminately misused. Research design, data, and methodology - This research conducted a literature review. For this, we summarized the meaningful and consistent arguments and drew up guidelines and suggested procedures for rigorous EFA. Results - PCA can be used instead of common factor analysis when all measured variables have high communality. However, common factor analysis is recommended for EFA. First, researchers should evaluate the sample size and check for sampling adequacy before conducting factor analysis. If these conditions are not satisfied, then the next steps cannot be followed. Sample size must be at least 100 with communality above 0.5 and a minimum subject to item ratio of at least 5:1, with a minimum of five items in EFA. Next, Bartlett's sphericity test and the Kaiser-Mayer-Olkin (KMO) measure should be assessed for sampling adequacy. The chi-square value for Bartlett's test should be significant. In addition, a KMO of more than 0.8 is recommended. The next step is to conduct a factor analysis. The analysis is composed of three stages. The first stage determines a rotation technique. Generally, ML or PAF will suggest to researchers the best results. Selection of one of the two techniques heavily hinges on data normality. ML requires normally distributed data; on the other hand, PAF does not. The second step is associated with determining the number of factors to retain in the EFA. The best way to determine the number of factors to retain is to apply three methods including eigenvalues greater than 1.0, the scree plot test, and the variance extracted. The last step is to select one of two rotation methods: orthogonal or oblique. If the research suggests some variables that are correlated to each other, then the oblique method should be selected for factor rotation because the method assumes all factors are correlated in the research. If not, the orthogonal method is possible for factor rotation. Conclusions - Recommendations are offered for the best factor analytic practice for empirical research.

    Impact of Adjuvant Chemotherapy in Elderly Breast Patients in Taiwan, A Hospital-Based Study

    • Lee, Hsiu Chuan;Chen, Wei Yu;Huang, Wen Tsung;Cheng, Kuo Chen;Tian, Yu Feng;Ho, Chung Han;Tsao, Chao Jung;Feng, Yin Hsun
      • Asian Pacific Journal of Cancer Prevention
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      • v.17 no.10
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      • pp.4591-4597
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      • 2016
    • Purpose: Decisions as to whether to provide adjuvant treatment in older breast cancer patients remains challenging. Side effects of chemotherapy have to be weighed against life expectancy, comorbidities, functional status, and frailty. To aid decision-making, we retrospectively analyzed 110 women with breast cancer treated with a curative intention from 2006 to 2012. Survival data with clinical and pathological parameters were evaluated to address the role of adjuvant chemotherapy in this study population. Method: A total of 110 elderly (>70 years) patients that received mastectomy at two hospitals in Taiwan were observed retrospectively for a medium of 51 months. After mastectomy, patients received conservative treatment or adjuvant chemotherapy, or hormone therapy following clinical guidelines or physician's preference. Data were collected from the cancer registry system. Results: Median age at diagnosis was 75.7 years. Thirty-five percent of patients received adjuvant chemotherapy, these having a significantly younger age ($mean=74.0{\pm}5.3$ vs $77.5{\pm}5.3$, p<0.001) and higher tumor staging (p=0.003) compared with their non-chemotherapy counterparts.Five-year overall survival was non-significantly higher in patients who received adjuvant chemotherapy (with chemotherapy 64.2% vs without chemotherapy 62.6%, p=0.635), while five-year recurrence free survival was non-significantly lower (with chemotherapy 64.1% vs without chemotherapy 90.5%, p=0.80). Conclusions: In this analysis, adjuvant chemotherapy tended to be given to patients with a younger age and higher tumor staging at our institute. It was not associated with any statistically significant improvement in survival and recurrence rate. Until age specific recommendations are available, physicians must use their clinical judgment and assess the tumor biology with the patient's comorbidities to make the best choice. Clinical trials focusing on this critical issue are warranted.

    Evaluation of Peri-procedural Anticoagulation Drug Therapy undergoing Radiofrequency Ablation in Patients with Atrial Fibrillation (심방세동 환자의 고주파 도자절제술 전.후의 항응고약물요법 사용실태 분석)

    • Kim, Su-Hyun;An, Sung-Shim;Kim, Soon-Joo;Bang, Joon-Seok;La, Hyen-Oh
      • Korean Journal of Clinical Pharmacy
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      • v.20 no.2
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      • pp.159-164
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      • 2010
    • Radiofrequency ablation (RA) is being used to manage atrial fibrillation (AF) with patients failed at the $1^{st}$-line anti-arrhythmic medications. Patients undergoing this procedure are at increased risk of thromboembolism after ablation, and anticoagulation management surrounding the ablation remains controversial. Although no conclusive recommendations can be made, published guidelines and data support therapeutic anticoagulation with warfarin. The purpose of this study was to analyze effectiveness of current therapy and to find factors fluctuate International Normalized Ratio (INR) values in patients undergone RA followed by anticoagulation service (ACS). Retrospective review was conducted utilizing database in a hospital. Among 110 patients under warfarin around ablation between January 2006 to September 2007, 54 patients were selected and allocated into 2 groups: Group A included 47 who discontinued warfarin after ablation, while 7 in B continued the medication. Information on demographics, amount and length of warfarin dosing, INR values and measuring frequencies, and the causing factors on INR fluctuation were abstracted. Differences were analyzed using chi-squared test, Fisher's Exact test, and unpaired Student t-test. Mean amount of warfarin before and after surgery was 4.0 mg, 4.1 mg in Group A and was 5.1 mg, 4.6 mg in Group B, respectively. Average duration of warfarin doing before ablation was 73.7 days in Group A, 129.9 days in B with no significant difference (p = 0.312). The duration time of warfarin on groups after ablation lasted several months. The number of checking INRs was 4.1 and 7.6, respectively. Inter-individual variability of INR fluctuations were $2.1{\pm}0.6$ in Group A and $2.2{\pm}0.7$ in B which were not significantly different (p = 0.062). 164 cases of decreased INR were: 'omission in taking medication, stressfulness and headache, 'increased intake of high vitamin K foods', 'lifestyle change of increased physical activities', and 'increase of food-intakes'. To the contrary, 36 cases of increased INR were: 'reduce of food-intake', 'use of non-prescription drugs', 'reduction in physical activities', and 'excessive restriction on food-intake', consecutively. In conclusion, the study validated therapeutic outcomes of RA patients who we treated with standard guideline and demonstrated 9 factors of INR fluctuations in the patient. A well-trained, pharmacist-monitored anticoagulation service could reduce the risk of adverse effects and prevent complications in patients with AF around RA operation.

    Intake of antioxidants and B vitamins is inversely associated with ischemic stroke and cerebral atherosclerosis

    • Choe, Hansaem;Hwang, Ji-Yun;Yun, Jin A;Kim, Ji-Myung;Song, Tae-Jin;Chang, Namsoo;Kim, Yong-Jae;Kim, Yuri
      • Nutrition Research and Practice
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      • v.10 no.5
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      • pp.516-523
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      • 2016
    • BACKGROUND/OBJECTIVES: This study was conducted to examine relationships between dietary habits and intakes of antioxidants and B vitamins and the risk of ischemic stroke, and to compare dietary factors according to the presence of cerebral artery atherosclerosis and stroke subtypes. SUBJECTS/METHODS: A total of 147 patients and 144 control subjects were recruited consecutively in the metropolitan area of Seoul, Korea. Sixty participants each in the case and control groups were included in analyses after 1:1 frequency matching. In addition, 117 acute ischemic stroke patients were classified into subtypes according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) guidelines. Dietary intake was measured using a semi-quantitative food frequency questionnaire composed of 111 food items and plasma lipid and homocysteine levels were analyzed. RESULTS: When compared with control subjects, stroke patients had unfavorable dietary behaviors and lower intakes of fruits ($73.1{\pm}83.2g$ vs. $230.9{\pm}202.1g$, P < 0.001), vegetables ($221.1{\pm}209.0g$ vs. $561.7{\pm}306.6g$, P < 0.001), and antioxidants, including vitamins C, E, $B_6$, ${\beta}$-carotene, and folate. The intakes of fruits, vegetables, vitamin C, and folate were inversely associated with the risk of ischemic stroke after adjusting for confounding factors. Intakes of vegetables, vitamins C, $B_6$, $B_{12}$, and folate per 1,000 kcal were lower in ischemic stroke with cerebral atherosclerosis than in those without. Overall vitamin $B_{12}$ intake per 1,000 kcal differed according to the TOAST classification (P = 0.004), but no differences among groups existed based on the post-hoc test. CONCLUSIONS: When compared with control subjects, ischemic stroke patients, particularly those with cerebral atherosclerosis, had unfavorable dietary intake, which may have contributed to the development of ischemic stroke. These results indicate that proper dietary recommendations are important for the prevention of ischemic stroke.

    Key Factors of the Utilization and Improvement in the National-level Technology Roadmap (국가수준 기술로드맵의 활용도 및 개선사항 영향요인)

    • Park, Sang-Moon;Byun, Do-Young;Son, Seok-Ho
      • Journal of Korea Technology Innovation Society
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      • v.10 no.1
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      • pp.143-164
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      • 2007
    • This paper investigates key factors on the utilization and improvement directions of national-level technology roadmaps for technology strategies. There are increasing interest in technology roadmaps to respond to uncertain environment and explore some possible directions of future technology development. To challenge the catching-up status in innovation, technology roadmap have been widely developed both in private and public sectors. In spite of recent increasing adoption of technology roadmap, there are few empirical studies on the level of utilization and improvement directions of technology roadmap with the viewpoints from science and technology experts in national innovation system. Most of studies on technology roadmaps have argued normative recommendations and made suggestions based on case studies. This paper examines the key factors on the utilization and future direction of national-level technology roadmaps. Based on survey from 320 experts in science and technology area, this paper analyzes the level of utilitation and future improvements of national level technology roadmap. The level of technological capabilities and participation experience on the roadmap development process have significant impact on the utilization of national-level technology roadmaps. Also there are three future directions to increase the usage of national-level technology roadmaps. The national-level technology roadmap should be improved as a more systematic processes including planning, progress, and outputs. Finally, this paper suggests some implications and future guidelines for national-level technology roadmaps.

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    Study on the Amendment of Standard Regulations of Food Additives and Contaminants for Infant Formulas in Korea (우리나라 영.유아용 조제식의 식품첨가물과 오염물질 기준 개선방안 연구)

    • Moon, Ji-Hea;Lee, Heon-Ok;Shim, Jae-Young;Kim, In-Hye;Shin, Hye-Seoung;Won, Sun-Im;Paik, Min-Kyoung;Shin, Hyoung-Soo;Om, Ae-Son
      • Journal of the Korean Society of Food Science and Nutrition
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      • v.37 no.9
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      • pp.1214-1221
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      • 2008
    • The aim of this study is to propose suggestions for establishing Korean regulatory standards of infant formula. Accordingly, the regulatory standards for food contaminants and additives in Korean infant formulas were compared and analyzed with those in CODEX, EU, Australia and New Zealand. Several suggestions for regulations were found from different countries. Firstly, it is advisable that additives for nutrient supplement of infant formula be classified as types of nutrients. Secondly, it is proposed that guidelines should be set on the maximum amount of additives in infant formula. Thirdly, pathogens such as Staphylococci and Salmonella of infant formula should be regulated. Finally, present regulations need to establish the maximum permissible levels of some pesticides, Pb and Al, that other countries are already regulating. These proposed recommendations would broaden the scope of infant formula regulatory standards needed for infants' health.