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김용수(Yong Soo Kim),염봉진(Bong-Jin Yum),Norman Kim 대한산업공학회 2010 대한산업공학회지 Vol.36 No.3
The recommender system is a typical software solution for personalized services which are now popular in e-commerce sites. Most of the existing recommender systems are based on customers’ explicit rating data on items (e.g., ratings on movies), and it is only recently that recommender systems based on implicit ratings have been proposed as a better alternative. Implicit ratings of a customer on those items that are clicked but not purchased can be inferred from the customer’s navigational and behavioral patterns. In this article, a dimensionality reduction (DR) technique is newly applied to the implicit rating-based recommender system, and its effectiveness is assessed using an experimental e-commerce site. The experimental results indicate that the performance of the proposed approach is superior or at least similar to the conventional collaborative filtering (CF)-based approach unless the number of recommended products is ‘large.’ In addition, the proposed approach requires less memory space and is computationally more efficient.
Gas holdup and hydrodynamic flow regime transition in bubble columns
Dong Hyun Lee,Jun Young Kim,Bongjun Kim,Nam-Sun Nho,Kang-Seok Go,Woohyun Kim,Jong Wook Bae,Sung Woo Jeong,Norman Epstein 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.56 No.-
The homogeneous-to-heterogeneousflow regime transition point dependence on gas and liquidproperties was investigated in a semi-cylindrical bubble column of 1.8 m height and 0.21 m innerdiameter operating as a semi-batch system. He, air, and CO2 gases were injected at superficial gasvelocities of up to 239 mm/s. The batch liquids included water, aqueous ethanol solutions, and aqueousglycerol solutions, all with a gas-free liquid height settled at 1 m. When the gas density increased, the gasholdup increased at all superficial gas velocities, delaying theflow regime transition. The gas holdups inthe liquid mixtures were higher than those for tap water. The transition gas holdup for the ethanolsolutions increased to a sharp maximum and then decreased as the surface tension increased. Also, theglycerol solutions showed similar behavior with respect to increasing liquid viscosity, but with ashallower maximum. The transition gas holdup was empirically correlated as a function of the gasdensity, surface tension, and liquid viscosity, employing dimensional constants. The measured transitiongas holdups for liquid mixtures, as well as some data from the literature, werefitted by the correlation.
소화성 궤양 환자의 혈중 및 요중 aluminum과 silicon
신해림,김정일,김두희,최석렬,서정일,김준연,Shin, Hae-Rim,Kim, Jung-Il,Kim, Doo-Hee,Choi, Suk-Ryol,Seoh, Jung-Il,Roberts, Norman B.,Kim, Joon-Youn 대한예방의학회 1999 Journal of Preventive Medicine and Public Health Vol.32 No.2
Objectives: This study was carried out to investigate the aluminum concentrations in blood, urine and drinking water, the factors which affect the concentrations and the role of silicon in patients who were taking antacid containing aluminum. Methods: We selected 122 peptic ulcer patients as cases and 144 healthy examinees as controls. Blood, urine, and drinking water were collected from the each study subject and we measured aluminum concentrations as well as silicon concentrations in the specimens. The factors including silicon affect on the aluminum concentrations were also analyzed, Results: 1. The mean duration of antacid administration was 12 months, and the mean daily and total amount of aluminum administration were 0.9 g and 304 g per each patient, respectively. 2. The blood and urine aluminum concentrations were significantly higher in the case. 3. The blood silicon concentration was significantly lower in the control group, and the urine silicon concentration was significantly higher in the case. 4. Urine aluminum concentration was significantly correlated with blood aluminum concentration (r=0.18), and urine silicon concentration was correlated with blood aluminum (r=0.19) and urine aluminum concentrations (r=0.13). 5. The longer the duration of antacid administration and the larger the total and daily amount of aluminum in the antacid were, the higher urine aluminum and silicon concentrations were, but not to a statistically significant degree. Conclusions: Blood and urine aluminum concentrations were higher in the ulcer patients. The authors suggest that follow-up studies of the patients who administered antacid with high aluminum content for long duration should be done.
SEP Performance Using Equivalence in Nakagami- <tex> $m$</tex> Fading Channels
Kim, Young Gil,Beaulieu, Norman C.,Woo-Kyung Lee IEEE 2016 IEEE Transactions on Vehicular Technology VT Vol.65 No.5
<P>We show that an L-branch maximal ratio combining (MRC) receiver with an average signal-to-noise ratio (SNR) (gamma) over bar in Nakagami-m fading channels is equivalent to an mL-branch MRC receiver with average SNR (gamma) over barm in Rayleigh fading channels in terms of symbol error probability (SEP) when mL is an integer. Moreover, the orthogonal space-time block code (OSTBC) employing M-t transmit antennas and M-r receive antennas with the average SNR (gamma) over bar in Nakagami-m fading channels is shown to be equivalent to an mM(t)M(r)-branch MRC single-input-multiple-output (SIMO) receiver with the average SNR (gamma) over bar mM(t) in Rayleigh fading channels.</P>
Kim, Young Gil,Beaulieu, Norman C. IEEE 2011 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.59 No.9
<P>The exact average bit error probability (BEP) performance of decode-and-forward (DF) cooperative systems for binary phase shift keying (BPSK) signals in Nakagami-m fading channels for integer values of m is analyzed. Two types of receivers, a λ-maximal ratio combining (λ-MRC) receiver and a piecewise linear (PL) receiver are examined. Closed-form, integral-free, expressions for the BEPs of the λ-MRC receiver and the PL receiver are obtained.</P>
소프트웨어 불법 다운로드와 청소년 소비자의 지위비행 및기타 비행행동 간의 차별화된 종단적 관계 고찰
김정은(Kim, Jung Eun),노만 B. 엡스틴(Norman B. Epstein) 한국소비문화학회 2017 소비문화연구 Vol.20 No.3
본 연구는 일반범죄이론과 문제행동이론에 근거하여 청소년의 소프트웨어 불법 다운로드에 미치는 두 가지 비행행동, 즉 지위비행과 기타 비행의 영향에 대해 알아보았다. 이 이론들에 기초하여 다른 변수들도 연구모 형에 투입되었다. 분석을 위해 2003년 이후로 매년 조사가 이루어진 한국청소년패널의 1차~4차년도 자료가 이용되었고, 시간에 따른 개인내 변화(within-individual changes)를 살펴보기 위해 고정효과모형에 초점을 둔 패널분석이 이루어졌다. 분석 결과, 소프트웨어 불법 다운로드와 지위비행 간에는 유의한 관계가 있었 으나, 기타의 비행행동들은 유의하지 않았다. 자아통제력과 자아존중감은 유의하였으나, 비행친구는 유의한 효과를 보이지 않았다. 부모애착과 심리적 건강문제는 유의하게 나타난 반면, 하루 컴퓨터 사용시간은 p < .08 수준에서 유의하였다. 남녀 각각에 대한 분석을 실시하여 성별차를 발견하였다. 연구결과는 한국의 사회 문화적 맥락에 근거하여 논의되고, 함의와 연구의 한계점에 대해서 언급하였다. This study examines influences of two types of offenses, juvenile status and other delinquent offenses, in adolescent software piracy, based on the General Theory of Crime and Problem Behavior Theory. Other variables were added to the model based on the theories. The 1 st to 4 th waves from the Korea Youth Panel Survey collected since 2003 were utilized for the analysis, and panel logistic analysis focusing on a fixed effects model was performed to examine within-individual changes over time. Findings showed a significant association of software piracy with juvenile status offense but not with other delinquent offenses. Self-control and self-esteem were significant influences, while delinquent friends showed no significant effect. Parental attachment and mental health problems were significant, while daily computer use was marginally significant (p < .08). Gender differences were discovered through gender-specific analyses. Results are discussed within the social and cultural context of South Korea, and implications and limitations are addressed.
Relay Advantage Criterion for Multihop Decode-and-Forward Relaying Systems
Young Gil Kim,Beaulieu, Norman C. IEEE 2014 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.13 No.4
<P>We define a symbol transition matrix (STM) as a matrix whose entries are the symbol transition probabilities of a relay in a decode-and-forward (DF) relaying system. Using the STM as a state transition matrix of a discrete-time Markov chain, the source-to-destination STM is shown to be the product of intermediate STMs in multihop DF relaying systems. We show that the probability of correct decision at the destination is the trace of the source-to-destination STM divided by the modulation order. The symbol error probabilities (SEPs) of multihop DF relaying systems with any modulation scheme in any independent and nonidentically distributed (ind) channels are derived using the STM. For multihop DF relaying systems in independent and identically distributed (iid) channels, the eigenvalues of the single link STM are used to simplify the calculation of the SEP for any modulation scheme. Also, the SEP of multihop DF relaying systems with 16-quadrature amplitude modulation (QAM) signals in ind Rayleigh fading channels is derived using the STM. A relay advantage criterion is derived for multihop DF relaying systems in iid Nakagami-m fading channels with both the total transmitted energy and the source-to-destination distance fixed. The relay advantage criterion can be used for deciding whether putting more relays between the source and the destination increases or decreases the SEP.</P>