박상인 교수

We develop a dynamic structural model of consumers' choices and producers' pricing in an oligopolistic market for newly introduced durable products with network externalities. The model is then applied to empirically analyze the de facto standardization of the VHS format in the U.S. home VCR market during 1981–1988. We find: (i) the network advantage of VHS explains at least 70.3% to 86.8% of (the logarithm of) relative sales of VHS to Betamax in each year; (ii) an increase in the network advant

In this paper, a two-step homogenization method is proposed and implemented for evaluating effective mechanical properties of lattice structured material fabricated by the material extrusion additive manufacturing process. In order to consider the characteristics of the additive manufacturing process in estimation procedures, the levels of scale for homogenization are divided into three stages — the levels of layer deposition, structural element, and lattice structure. The method consists of two

An integrated multiscale modeling framework that incorporates a simulation-based upscaling technique is developed and implemented for the material characterization of additively manufactured cellular structures in this paper. The proposed upscaling procedure enables the determination of homogenized parameters at multiple levels by matching the probabilistic performance between fine and coarse scale models. Polynomial chaos expansion (PCE) is employed in the upscaling procedure to handle the comp

To obtain weight reduction and high performance, using level set based topology optimization in magnetic fields is promising for the design of magnetic actuators where the precise boundary shape and topological changes are required. This paper addresses a novel scheme to design the optimal configuration of a magnetic actuator for maximizing the actuating force applied at the location where the motion being controlled. Level set function is introduced to represent ferromagnetic material boundarie

The e-readiness indexes measured by accessibility and content have typically been employed in e-government website evaluations. We present empirical evidence from four e-readiness indexes (such as accessibility, e-information, e-petition and e-participation) and the clickstream website usage data of the Korean central government units from 2003 to 2005 to evaluate whether better e-readiness induces more use of e-government websites. We find that only the e-information index was significantly cor

The motor imagery (MI)-based brain-computer interface (BCI) is an intuitive interface that provides control over computer applications directly from brain activity. However, it has shown poor performance compared to other BCI systems such as P300 and SSVEP BCI. Thus, this study aimed to improve MI-BCI performance by training participants in MI with the help of sensory inputs from tangible objects (i.e., hard and rough balls), with a focus on poorly performing users. The proposed method is a hybr

Abstract Based on sensory conflict theory, motion sickness is strongly related to the information processing capacity or resources of the brain to cope with the multi-sensory stimuli experienced by watching virtual reality (VR) content. The purpose of this research was to develop a method of measuring motion sickness using the heart-evoked potential (HEP) phenomenon and propose new indicators for evaluating motion sickness. Twenty-eight undergraduate volunteers of both genders (14 females) parti

The phenomena of brain-computer interface-inefficiency in transfer rates and reliability can hinder development and use of brain-computer interface technology. This study aimed to enhance the classification performance of motor imagery-based brain-computer interface (three-class: left hand, right hand, and right foot) of poor performers using a hybrid-imagery approach that combined motor and somatosensory activity. Twenty healthy subjects participated in these experiments involving the following

2003년 말 현재 한국의 지방상수도사업은 167개 지방자치단체별로 운영되고 있으며, 7대 특별ㆍ광역시를 제외할 경우 평균 급수인구 약 10만 명 내외의 영세규모이다. 본 논문은 한국 상수도산업의 적정 광역화 범위에 대한 실증적 단초를 제공하고자 한다. 본 논문은 상수도물 생산과정에 대한 고찰에서 출발해 노동투입함수를 유도한 후, 행정자치부에서 발행하는 “지방 공기업 결산 및 경영평가(2001년)”와 환경부에서 발행하는 “상수도통계 (2001년)”의 자료를 이용해 노동투입함수를 추정한다. 분석결과 노동투입에 규모의 경제가 존재하며, 이는 주로 취ㆍ정수장 운영이나 중앙관리, 그리고 관로의 유지 및 보수에 고정적 노동투입이 필요하고, 사업규모가 큰 경우 규모가 큰 취ㆍ정수장을 사용하거나 급수가구 밀집지역에 직경이 큰 관로를 사용함으로써 상수도물 산출량 단위당 노동 투입량이 감소하는데 따른 것으로 보인다. 이러한 규모의 경제의 존재는 동일 수계 내 인접한 소규모 지역들에 있어 사업 광역화

Pupillary responses are associated with affective processing, cognitive function, perception, memory, attention, and other brain activities involving neural pathways. The present study aimed to develop a noncontact system to measure brain activity based on pupillary rhythms using an infra-red web camera. Electroencephalogram (EEG) signals and pupil imaging of 70 undergraduate volunteers (35 female, 35 male) were measured in response to sound stimuli designed to evoke arousal, relaxation, happine