• Title/Summary/Keyword: Area Weighted Method

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Image Processing and Deep Learning Techniques for Fast Pig's Posture Determining and Head Removal (돼지의 빠른 자세 결정과 머리 제거를 위한 영상처리 및 딥러닝 기법)

  • Ahn, Hanse;Choi, Wonseok;Park, Sunhwa;Chung, Yongwha;Park, Daihee
    • KIPS Transactions on Software and Data Engineering
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    • v.8 no.11
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    • pp.457-464
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    • 2019
  • The weight of pig is one of the main factors in determining the health and growth state of pigs, their shipment, the breeding environment, and the ration of feed, and thus measuring the pig's weight is an important issue in productivity perspective. In order to estimate the pig's weight by using the number of pig's pixels from images, acquired from a Top-view camera, the posture determining and the head removal from images are necessary to measure the accurate number of pixels. In this research, we propose the fast and accurate method to determine the pig's posture by using a fast image processing technique, find the head location by using a fast deep learning technique, and remove pig's head by using light weighted image processing technique. First, we determine the pig's posture by comparing the length from the center of the pig's body to the outline of the pig in the binary image. Then, we train the location of pig's head, body, and hip in images using YOLO(one of the fast deep learning based object detector), and then we obtain the location of pig's head and remove an outside area of head by using head location. Finally, we find the boundary of head and body by using Convex-hull, and we remove pig's head. In the Experiment result, we confirmed that the pig's posture was determined with an accuracy of 0.98 and a processing speed of 250.00fps, and the pig's head was removed with an accuracy of 0.96 and a processing speed of 48.97fps.

Estimation of genetic correlations and genomic prediction accuracy for reproductive and carcass traits in Hanwoo cows

  • Md Azizul Haque;Asif Iqbal;Mohammad Zahangir Alam;Yun-Mi Lee;Jae-Jung Ha;Jong-Joo Kim
    • Journal of Animal Science and Technology
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    • v.66 no.4
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    • pp.682-701
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    • 2024
  • This study estimated the heritabilities (h2) and genetic and phenotypic correlations between reproductive traits, including calving interval (CI), age at first calving (AFC), gestation length (GL), number of artificial inseminations per conception (NAIPC), and carcass traits, including carcass weight (CWT), eye muscle area (EMA), backfat thickness (BF), and marbling score (MS) in Korean Hanwoo cows. In addition, the accuracy of genomic predictions of breeding values was evaluated by applying the genomic best linear unbiased prediction (GBLUP) and the weighted GBLUP (WGBLUP) method. The phenotypic data for reproductive and carcass traits were collected from 1,544 Hanwoo cows, and all animals were genotyped using Illumina Bovine 50K single nucleotide polymorphism (SNP) chip. The genetic parameters were estimated using a multi-trait animal model using the MTG2 program. The estimated h2 for CI, AFC, GL, NAIPC, CWT, EMA, BF, and MS were 0.10, 0.13, 0.17, 0.11, 0.37, 0.35, 0.27, and 0.45, respectively, according to the GBLUP model. The GBLUP accuracy estimates ranged from 0.51 to 0.74, while the WGBLUP accuracy estimates for the traits under study ranged from 0.51 to 0.79. Strong and favorable genetic correlations were observed between GL and NAIPC (0.61), CWT and EMA (0.60), NAIPC and CWT (0.49), AFC and CWT (0.48), CI and GL (0.36), BF and MS (0.35), NAIPC and EMA (0.35), CI and BF (0.30), EMA and MS (0.28), CI and AFC (0.26), AFC and EMA (0.24), and AFC and BF (0.21). The present study identified low to moderate positive genetic correlations between reproductive and CWT traits, suggesting that a heavier body weight may lead to a longer CI, AFC, GL, and NAIPC. The moderately positive genetic correlation between CWT and AFC, and NAIPC, with a phenotypic correlation of nearly zero, suggesting that the genotype-environment interactions are more likely to be responsible for the phenotypic manifestation of these traits. As a result, the inclusion of these traits by breeders as selection criteria may present a good opportunity for developing a selection index to increase the response to the selection and identification of candidate animals, which can result in significantly increased profitability of production systems.

Ecosysteme de I′Etang de Berre (Mediterranee nord-occidentale) : Caracteres Generales Physiques, Chimiques et Biologiques

  • Kim, Ki-Tai
    • Korean Journal of Environmental Biology
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    • v.22 no.2
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    • pp.247-258
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    • 2004
  • Climatological, hydrological and planktonical research studies, measurements of primary production and photosynthetic efficiency from December 1976 to December 1978 have been carried out in two brackish lakes: Lake Etang de Berre and Lake Etang de Vaine located in the French Mediterranean coast, in the region of Carry-le-Rouet located on the north-west Mediterranean near Marseilles, and in fresh water inflows from 4 Rivers (Touloubre, Durance, Arc, Durancole) to Lake Etang de Berre. Physico-chemical parameters were measured for this study: water temperature, salinity, density, pH, alcalinity, dissolved oxygen (% saturation), phosphate, nitrate, nitrite, silicate etc. Diverse biological parameters were also studied: photosynthetic pigments, phaeopigments, specific composition and biomass of phytoplankton, primary pelagic production etc. Climatical factors were studied: air-temperature, solar-radiation, evaporation, direction (including strength) of winds, precipitation and freshwater volume of the four rivers. The changes in Lake ‘Etang de Berre’ ecosystem depend on the quality of the water in the Durance River, and on the effects of seawater near the entrance of the Caronte Canal. The water quality of the lake varies horizontally and vertically as a result of atmospheric phenomena, maritime currents and tides. The distribution of water temperatures is generally heterogeneous. Southeasterly winds and the Northeasterly Mistral wind are important in the origins of circulated and mixed water masses. These winds are both frequent and strong. They have, as a result, a great effect on the water environment of Lake Etang de Berre. In theory, the annual precipitation in this region is well over eight times the water mass of the lake. The water of the Durance River flows into Lake Etang de Berre through the EDF Canal, amounting to 90% of the precipitation. However, reduction of rainfall in dry seasons has a serious effect on the hydrological characteristics of the lake. The temperature in the winter is partially caused by the low temperature of fresh water, particularly that of the Durance River. The hydrological season of fresh and brackish water is about one month ahead of the hydrological season of sea water in its vicinity. The salinity of Lake Etang de Berre runs approximately 3$\textperthousand$, except at lower levels and near the entrance to the Caronte Canal. However, when the volume of the Durance River water is reduced in the summer and fall, the salinity rises to 15$\textperthousand$. In the lake, the ratio of fresh water to sea water is six to one (6:1). The large quantities of seston conveyed by rivers, particularly the Durance diversion, strongly reduce the transparency in the brackish waters. Although the amount of sunshine is also notable, transparency is slight because of the large amount of seston, carried chiefly by Tripton in the fresh water of the Durance River. Therefore, photosynthesis generally occurs only in the surface layer. The transparency progressively increases from freshwater to open seawater, as mineral particles sink to the bottom (about 1.7kg $m^{-2}a^{-1}$ on the average in brackish lakes). The concentration of dissolved oxygen and the rate of oxygen saturation in seawater (Carry-le-Rouet) ranged from 5.0 to 6.0 $m\ell$ㆍ.$1^{-1}$, and from 95 to 105%, respectively. The amount of dissolved oxygen in Etang de Berre oscillated between 2.9 and 268.3%. The monographs of phosphate, nitrate, nitrite and silicate were published as a part of a study on the ecology of phytoplankton in these environments. Horizontal and vertical distributions of these nutriments were studied in detail. The recent diversion of the Durance River into Lake Etang de Berre has effected a fundamental change in this formerly marine environment, which has had a great impact in its plankton populations. A total of 182 taxa were identified, including 111 Bacillariophyceae, 44 Chlorophyceae, and 15 Cyanophyceae. The most abundant species are small freshwater algae, mainly Chlorophyceae. The average density is about $10^{8}$ cells $1^{-1}$ in Lake Etang de Berre, and about double that amount in Lake Etang de Vaine. Differences in phytoplankton abundance and composition at the various stations or at various depths are slight. Cell biovolume V (equivalent to true biomass), plasma volume VP (‘useful’ biomass) and, simultaneously. the cell surface area S and S/V ratio through the measurement of cell dimensions were computed as the parameters of phytoplankton productivity and metabolism. Pigment concentrations are generally very high on account of phytoplankton blooms by Cyanophyceae, Chlorophyceae and Cryptophyceae. On the other hand, in freshwaters and marine waters, pigment concentrations are comparatively low and stable, showing slight annual variation. The variations of ATP concentration were closely related to those of chlorophyll a and phytoplankton blooms only in marine waters. The carbon uptake rates ranged between 38 and 1091 mg$Cm^{-2}d^{-1}$, with an average surface value of 256 mg; water-column carbon-uptake rates ranged between 240 and 2310 mg$Cm^{-2}d^{-1}$, with an average of 810, representing 290 mg$Cm^{-2}$, per year 45 000 tons per year of photosynthetized carbon for the whole lake. Gross photosynthetic production measured by the method of Ryther was studied over a 2-year period. The values obtained from marine water(Carry-le-Rouet) ranged from 23 to 2 337 mg$Cm^{-2}d^{-1}$, with a weighted average of 319, representing about 110 gCm$^{-2}$ per year. The values in brakish water (Etang de Berre) ranged from 14 to 1778 mg$Cm^{-2}d^{-1}$, with a weighted average of 682, representing 250 mg$Cm^{-2}$ per year and 38 400 tons per year of photosynthesized carbon for the whole lake.

Recent updated diagnostic methods for esophageal motility disorders (식도의 운동장애에 관한 최신지견)

  • Yoon, Seok-Hwan
    • Journal of radiological science and technology
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    • v.27 no.4
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    • pp.11-16
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    • 2004
  • Classification of esophageal motility disorders not yet finalized and is still ongoing as the new disorders are reported, and the existing classification is changed or removed. In terms of radiology, the primary peristalsis does not exist, and the lower end of the esophagus show the smooth, tapered, beak-like appearance. The esophageal motility disorder, which mostly occurs in the smooth muscle area, show the symptoms of reduction or loss (hypomotility) or abnormal increase (hypermotility) of peristalsis of the esophagus. It is important to understand the anatomy and physiology of the esophagus for the appropriate radiological method and diagnosis. Furthermore, the symptom of the patient and the manometry finding must be closely referred for the radiological diagnosis. The lower esophageal sphincter can be normally functioning and open completely as the food moves lower. Sperandio M et al. argues that the name diffuse esophageal spasm must be changed to distal esophageal spasm (DES) as most of the spasm occurs in the distal esophagus, composed of the smooth muscle. According to Ott et al., usefulness of barium method for diagnosing the esophageal motility disorder is Achalasia 95%, DES 71% and NEMD 46%, with the overall sensitivity of 56%. However, excluding the nutcracker esophagus or nonspecific disorder which cannot be diagnosed with the radiological methods, the sensitivity increases to 89%. Using videofluoroscopy and 5 time swallows, the average sensitivity was over 90%. In conclusion, the barium method is a simple primary testing method for esophageal motility test. Using not only the image but also the videofluoroscopy with good knowledge of the anatomy and physiology, it is believed that the method will yield the accurate diagnosis.

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Methodology of Selecting Criteria for Pedestrian only Street (차없는 거리 선정기준 수립을 위한 방법론 정립 연구)

  • Kim, Yoomi;Park, Jejin;Lee, Junyoung;Ha, Taejun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.5
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    • pp.867-879
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    • 2016
  • Since the 1970s, the region of its own pedestrian center and environmental pollution caused by exhaust gases have been reduced gradually in a continuous increase of the vehicle, school route the central business district, around the school, the sidewalk where the vehicle do not pass, facilities of minimum for the safety of pedestrians and systematic management of an area where an unspecified number and alleys impassable is insufficient. Recently, in response to the "Law for convenience enhancing safety and walking" is enforced in Korea, research on Pedestrian only Street has been actively about the government, the standard for calculating the weights of evaluation associated with it. it is a actuality, however, there are insufficient, evaluation for business promotion is being conducted evaluation polite manner by using, for example, scale residence time and purpose of the passengers as there is no car that has been carried out on a voluntary basis through the municipality have. In this study, by suggesting a method for the selection of the street without a car, make a survey by placing a purpose in the selection method presentation of the street with no car to be construction future, was researching. F.G.I (Focus Group Interview) survey, professors, staff in urban, traffic field of experts in order to present the weights for the evaluation of the Pedestrian only Street by using the evaluation index by type of Pedestrian only Street, was interviewed about the evaluation index for the conducted for professionals engaged in the engineering company, and randomly selected 200 peoples, weighted evaluation of the street with Pedestrian only Street was proposed. By classifying the items purpose and goals of the evaluation type by this by applying the weight, and present the weight of the detailed indicators each corresponding to each item, and scored on the basis of the result, in this paper it can be so that one methodology for the selection standard for the construction as Pedestrian only Street, and the weight of the evaluation of the type that has been derived, the selection and evaluation methods and then added to these criteria to settle careful study of the reference should be performed further.

Problems in the Korean National Family Planning Program (한국가족계획사업(韓國家族計劃事業)의 문제점(問題點))

  • Hong, Jong-Kwan
    • Clinical and Experimental Reproductive Medicine
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    • v.2 no.2
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    • pp.27-36
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    • 1975
  • The success of the family planning program in Korea is reflected in the decrease in the growth rate from 3.0% in 1962 to 2.0% in 1971, and in the decrease in the fertility rate from 43/1,000 in 1960 to 29/1,000 in 1970. However, it would be erroneous to attribute these reductions entirely to the family planning program. Other socio-economic factors, such as the increasing age at marriage and the increasing use of induced abortions, definitely had an impact on the lowered growth and fertility rate. Despite the relative success of the program to data in meeting its goals, there is no room for complacency. Meeting the goal of a further reduction in the population growth rate to 1.3% by 1981 is a much more difficult task than any one faced in the past. Not only must fertility be lowered further, but the size of the target population itself will expand tremendously in the late seventies; due to the post-war baby boom of the 1950's reaching reproductive ages. Furthermore, it is doubtful that the age at marriage will continue to rise as in the past or that the incidence of induced abortion will continue to increase. Consequently, future reductions in fertility will be more dependent on the performance of the national family planning program, with less assistance from these non-program factors. This paper will describe various approaches to help to the solution of these current problems. 1. PRACTICE RATE IN FAMILY PLANNING In 1973, the attitude (approval) and knowledge rates were quite high; 94% and 98% respectively. But a large gap exists between that and the actual practice rate, which is only 3695. Two factors must be considered in attempting to close the KAP-gap. The first is to change social norms, which still favor a larger family, increasing the practice rate cannot be done very quickly. The second point to consider is that the family planning program has not yet reached all the eligible women. A 1973 study determineded that a large portion, 3096 in fact, of all eligible women do not want more children, but are not practicing family planning. Thus, future efforts to help close the KAP-gap must focus attention and services on this important large group of potential acceptors. 2. CONTINUATION RATES Dissatisfaction with the loop and pill has resulted in high discontinuation rates. For example, a 1973 survey revealed that within the first six months initial loop acceptance. nearly 50% were dropouts, and that within the first four months of inital pill acceptance. nearly 50% were dropouts. These discontinuation rates have risen over the past few years. The high rate of discontinuance obviously decreases the contraceptive effectiveness. and has resulted in many unwanted births which is directly related to the increase of induced abortions. In the future, the family planning program must emphasize the improved quality of initial and follow-up services. rather than more quantity, in order to insure higher continuation rates and thus more effective contraceptive protection. 3. INDUCED ABORTION As noted earlier. the use of induced abortions has been increase yearly. For example, in 1960, the average number of abortions was 0.6 abortions per women in the 15-44 age range. By 1970. that had increased to 2 abortions per women. In 1966. 13% of all women between 15-44 had experienced at least one abortion. By 1971, that figure jumped to 28%. In 1973 alone, the total number of abortions was 400,000. Besides the ever incre.sing number of induced abortions, another change has that those who use abortions have shifted since 1965 to include- not. only the middle class, but also rural and low-income women. In the future. in response to the demand for abortion services among rural and low-income w~men, the government must provide and support abortion services for these women as a part of the national family planning program. 4. TARGET SYSTIi:M Since 1962, the nationwide target system has been used to set a target for each method, and the target number of acceptors is then apportioned out to various sub-areas according to the number of eligible couples in each area. Because these targets are set without consideration for demographic factors, particular tastes, prejudices, and previous patterns of acceptance in the area, a high discontinuation rate for all methods and a high wastage rate for the oral pill and condom results. In the future. to alleviate these problems of the methodbased target system. an alternative. such as the weighted-credit system, should be adopted on a nation wide basis. In this system. each contraceptive method is. assigned a specific number of points based upon the couple-years of protection (CYP) provided by the method. and no specific targets for each method are given. 5. INCREASE OF STERILIZA.TION TARGET Two special projects. the hospital-based family planning program and the armed forces program, has greatly contributed to the increasing acceptance in female and male sterilization respectively. From January-September 1974, 28,773 sterilizations were performed. During the same time in 1975, 46,894 were performed; a 63% increase. If this trend continues, by the end of 1975. approximately 70,000 sterilizations will have been performed. Sterilization is a much better method than both the loop and pill, in terms of more effective contraceptive protection and the almost zero dropout rate. In the future, the. family planning program should continue to stress the special programs which make more sterilizations possible. In particular, it should seek to add the laparoscope techniques to facilitate female sterilization acceptance rates. 6. INCREASE NUMBER OF PRIVATE ACCEPTORS Among the current family planning users, approximately 1/3 are in the private sector and thus do not- require government subsidy. The number of private acceptors increases with increasing urbanization and economic growth. To speed this process, the government initiated the special hospital based family planning program which is utilized mostly by the private sector. However, in the future, to further hasten the increase of private acceptors, the government should encourage doctors in private practice to provide family planning services, and provide the contraceptive supplies. This way, those do utilize the private medical system will also be able to receive family planning services and pay for it. Another means of increasing the number of private acceptors, IS to greatly expand the commercial outlets for pills and condoms beyond the existing service points of drugstores, hospitals, and health centers. 7. IE&C PROGRAM The current preferred family size is nearly twice as high as needed to achieve a stable poplation. Also, a strong boy preference hinders a small family size as nearly all couples fuel they must have at least one or more sons. The IE&C program must, in the future, strive to emphasize the values of the small family and equality of the sexes. A second problem for the IE&C program to work. with in the: future is the large group of people who approves family planning, want no more children, but do not practice. The IE&C program must work to motivate these people to accept family planning And finally, for those who already practice, an IE&C program in the future must stress continuation of use. The IE&C campaign, to insure highest effectiveness, should be based on a detailed factor analysis of contraceptive discontinuance. In conclusion, Korea faces a serious unfavorable sociodemographic situation- in the future unless the population growth rate can be curtailed. And in the future, the decrease in fertility will depend solely on the family planning program, as the effect of other socio-economic factors has already been maximumally felt. A second serious factor to consider is the increasing number of eligible women due to the 1950's baby boom. Thus, to meet these challenges, the program target must be increased and the program must improve the effectiveness of its current activities and develop new programs.

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Functional MRI of Visual Cortex: Correlation between Photic Stimulator Size and Cortex Activation (시각피질의 기능적 MR 연구: 광자극 크기와 피질 활성화와의 관계)

  • 김경숙;이호규;최충곤;서대철
    • Investigative Magnetic Resonance Imaging
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    • v.1 no.1
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    • pp.114-118
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    • 1997
  • Purpose: Functional MR imaging is the method of demonstrating changes in regional cerebral blood flow produced by sensory, motor, and any other tasks. Functional MR of visual cortex is performed as a patient stares a photic stimulation, so adaptable photic stimulation is necessary. The purpose of this study is to evaluate whether the size of photic stimulator can affect the degree of visual cortex activation. Materials and Methods: Functional MR imaging was performed in 5 volunteers with normal visual acuity. Photic stimulator was made by 39 light-emitting diodes on a plate, operating at 8Hz. The sizes of photic stimulator were full field, half field and focal central field. The MR imager was Siemens 1.5-T Magnetom Vision system, using standard head coil. Functional MRI utilized EPI sequence (TR/TE= 1.0/51. Omsec, matrix $No.=98{\times}128$, slice thickness=8mm) with 3sets of 6 imaging during stimulation and 6 imaging during rest, all 36 scannings were obtained. Activation images were obtained using postprocessing software(statistical analysis by Z-score), and these images were combined with T-1 weighted anatomical images. The activated signals were quantified by numbering the activated pixels, and activation a index was obtained by dividing the pixel number of each stimulator size with the sum of the pixel number of 3 study using 3 kinds of stimulators. The correlation between the activation index and the stimulator size was analysed. Results: Mean increase of signal intensities on the activation area using full field photic stimulator was about 9.6%. The activation index was greatest on full field, second on half field and smallest on focal central field in 4. The index of half field was greater than that of full field in 1. The ranges of activation index were full field 43-73%(mean 55%), half field 22-40 %(mean 32%), and focal central field 5-24%(mean 13%). Conclusion: The degree of visual cortex activation increases with the size of photic stimulator.

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Comparative Analysis of GNSS Precipitable Water Vapor and Meteorological Factors (GNSS 가강수량과 기상인자의 상호 연관성 분석)

  • Jae Sup, Kim;Tae-Suk, Bae
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.33 no.4
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    • pp.317-324
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    • 2015
  • GNSS was firstly proposed for application in weather forecasting in the mid-1980s. It has continued to demonstrate the practical uses in GNSS meteorology, and other relevant researches are currently being conducted. Precipitable Water Vapor (PWV), calculated based on the GNSS signal delays due to the troposphere of the Earth, represents the amount of the water vapor in the atmosphere, and it is therefore widely used in the analysis of various weather phenomena such as monitoring of weather conditions and climate change detection. In this study we calculated the PWV through the meteorological information from an Automatic Weather Station (AWS) as well as GNSS data processing of a Continuously Operating Reference Station (CORS) in order to analyze the heavy snowfall of the Ulsan area in early 2014. Song’s model was adopted for the weighted mean temperature model (Tm), which is the most important parameter in the calculation of PWV. The study period is a total of 56 days (February 2013 and 2014). The average PWV of February 2014 was determined to be 11.29 mm, which is 11.34% lower than that of the heavy snowfall period. The average PWV of February 2013 was determined to be 10.34 mm, which is 8.41% lower than that of not the heavy snowfall period. In addition, certain meteorological factors obtained from AWS were compared as well, resulting in a very low correlation of 0.29 with the saturated vapor pressure calculated using the empirical formula of Magnus. The behavioral pattern of PWV has a tendency to change depending on the precipitation type, specifically, snow or rain. It was identified that the PWV showed a sudden increase and a subsequent rapid drop about 6.5 hours before precipitation. It can be concluded that the pattern analysis of GNSS PWV is an effective method to analyze the precursor phenomenon of precipitation.

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.


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