Search

This paper is concerned with developing mean-field game models for the evolution of epidemics. Specifically, an agent's decision -- to be socially active in the midst of an epidemic -- is modeled as a mean-field game with health-related costs and activity-related rewards. By considering the fully and partially observed versions of this problem, the role of information in guiding an agent's rational decision is highlighted. The main contributions of the paper are to derive the equations for the mean-field game in both fully and partially observed settings of the problem, to present a complete analysis of the fully observed case, and to present some analytical results for the partially observed case.

본 연구는 노인의 인지기능 변화 형태와 영향요인을 파악하기 위하여 한국고령화패널 (Korean Longitudinal Study of Aging: KLoSA)의 4차년도부터 7차년도의 자료를 사용하였으며, 다변량 잠재성장모형으로 자료를 분석하였다. 분석대상은 4차(2012년) 기준 65세이상 85세이하 노인으로 최종 분석 대상자는 2012년부터 2018년까지의 추적조사에 응답한 노인 5,503명이다. 본 연구의 주요 결과는 다음과 같다. 노인의 인지기능은 선형으로 감소하는 것으로 나타났다. 노인의 인지기능변화에 영향을 미치는 요인은 성별, 연령, 혼인상태, 규칙적 운동참여, 운동횟수, 종교, 여가스포츠활동 이었다. 성별이 남성일 때 연령이 낮을수록, 배우자가 있을수록 인지기능 초기치가 높았다. 규칙적 운동참여와 운동횟수는 인지기능에 초기치와 변화율에 모두 유의미한 영향을 미쳤다. 즉 규칙적인 운동을 참여한 노인일수록 운동횟수가 높은 노인일수록 인지기능저하와 예방에 도움을 주는 변수로 나타났다. 종교가 있고, 여가스포츠활동 횟수가 높은 노인일수록 인지기능 초기치에 유의미한 영향을 미치는 것으로 나타났다. 연구결과를 바탕으로 노인의 인지기능저하 예방과 규칙적인 운동과 횟수, 여가스포츠활동의 활성화를 위한 이론적, 실천적 함의를 논의하였다.

The purpose of this study is to analyze how university students" leisure has changed before and after COVID-19, and whether leisure motivation and health belief have influenced leisure change. For this, data were collected from 235 university students in the Seoul and Gyounggi area. The research results analyzed through cross-analysis and hierarchical logistic regression are as follows. First, there were differences in leisure of university students before and after COVID-19. Compared to before, sports participation activities, cultural and arts viewing activities decreased, and recreational activities increased significantly. Based on the research results, the characteristics of leisure change of university students after COVID-19 can be called "game and media". Second, physical leisure motivation and social leisure motivation have been associated with changes in leisure of university students since COVID-19. Third, perceived benefit of health beliefs has influenced the leisure change of university students after COVID-19. Fourth, physical leisure motivation and perceived susceptibility of health belief showed an interaction effect on leisure changes of university students after COVID-19.

In this study, Bacillus sp. SRCM 112835 was isolated from soybean paste (Doenjang, Korean Fermented Soy Paste). Bacillus sp. SRCM 112835 showed biosorption of the Cu (II) in aqueous solution. The strain effectively absorbed 30.2% of the Cu (II) from a 52.3 mg/L within 60 min. The properties of the Bacillus sp. SRCM 112835 were investigated by Fourier transform infrared spectroscopy (FT-IR), point of zero charge (pHpzc), and phylogenetic analysis. The influence of initial pH (2.08-9.98) and biomass dosage (0.005-0.07 g) were likewise probed. Isotherm and kinetic experiment results suggested that the Langmuir isotherm and pseudo-second-order kinetic models well-fitted the experimental data, respectively.

This thesis is concerned with the stochastic filtering problem for a hidden Markov model (HMM) with the white noise observation model. For this filtering problem, we make three types of original contributions: (1) dual controllability characterization of stochastic observability, (2) dual minimum variance optimal control formulation of the stochastic filtering problem, and (3) filter stability analysis using the dual optimal control formulation. For the first contribution of this thesis, a backward stochastic differential equation (BSDE) is proposed as the dual control system. The observability (detectability) of the HMM is shown to be equivalent to the controllability (stabilizability) of the dual control system. For the linear-Gaussian model, the dual relationship reduces to classical duality in linear systems theory. The second contribution is to transform the minimum variance estimation problem into an optimal control problem. The constraint is given by the dual control system. The optimal solution is obtained via two approaches: (1) by an application of maximum principle and (2) by the martingale characterization of the optimal value. The optimal solution is used to derive the nonlinear filter. The third contribution is to carry out filter stability analysis by studying the dual optimal control problem. Two approaches are presented through Chapters 7 and 8. In Chapter 7, conditional Poincar\'e inequality (PI) is introduced. Based on conditional PI, various convergence rates are obtained and related to literature. In Chapter 8, the stabilizability of the dual control system is shown to be a necessary and sufficient condition for filter stability on certain finite state space model., Comment: Ph.D. Thesis of the author

This paper is concerned with the development and use of duality theory for a nonlinear filtering model with white noise observations. The main contribution of this paper is to introduce a stochastic optimal control problem as a dual to the nonlinear filtering problem. The mathematical statement of the dual relationship between the two problems is given in the form of a duality principle. The constraint for the optimal control problem is the backward stochastic differential equation (BSDE) introduced in the companion paper. The optimal control solution is obtained from an application of the maximum principle, and subsequently used to derive the equation of the nonlinear filter. The proposed duality is shown to be an exact extension of the classical Kalman-Bucy duality, and different from other types of optimal control and variational formulations given in literature.

This paper revisits the classical question of the stability of the nonlinear Wonham filter. The novel contributions of this paper are two-fold: (i) definition of the stabilizability for the (control-theoretic) dual to the nonlinear filter; and (ii) the use of this definition to obtain conclusions on the stability of the Wonham filter. Specifically, it is shown that the stabilizability of the dual system is necessary for filter stability and conversely stabilizability implies that the filter asymptotically detects the correct ergodic class. The formulation and the proofs are based upon a recently discovered duality result whereby the nonlinear filtering problem is cast as a stochastic optimal control problem for a backward stochastic differential equation (BSDE). The control-theoretic proof techniques and results may be viewed as a generalization of the classical work on the stability of the Kalman filter., 60th IEEE Conference on Decision and Control (CDC)

Introduction and Hypothesis: Photoactivation has emerged as an innovative therapeutic strategy for coronary high-risk plaque without metallic remnants, however, limited targetable ability of photoactivator and lack of imaging guidance hinders its application to clinics. To solve these unmet needs, we developed intravascular photoactivation strategy guided by dual-modal OCT-NIRF structural-molecular imaging using a novel theranostic NIRF-emitting photoactivator. Methods and Results: Photoactivatable NIRF-emitting theranostic agent targeting scavenger receptors on macrophages was newly synthesized. The intravascular photoactivation system based on fiber type cylindrical diffuser was newly fabricated for the therapeutic light delivery to the plaques. Forty-eight hours after intravenous injection of scale-up NIRF-emitting photoactivator (equivalent Ce6 dose of 2 mg/kg), OCT-NIRF imaging was able to exactly identify the highly inflamed targets in OCT-delineated plaques of rabbit arteries. Two weeks after therapeutic light irradiation through the catheter to the NIRF enhanced macrophages, the inflammatory NIRF signals of targeted atheroma markedly decreased as compared to the controls (Figure). By comprehensive immunofluorescence analysis, photoactivation produced a prominent increase in macrophage-associated apoptotic bodies and also induced autophagy with an enhanced efferocytosis, resulting in stabilization of the atheroma. Conclusions: Intravascular photoactivation using targeted NIRF emitting photosensitizer could stabilize the inflamed plaque under the guidance of OCT-NIRF imaging. This imaging guided therapeutic innovation will be a promising theranostic strategy for the high-risk coronary plaques.

This paper build on our recent work where we presented a dual stochastic optimal control formulation of the nonlinear filtering problem [1]. The constraint for the dual problem is a backward stochastic differential equations (BSDE). The solution is obtained via an application of the maximum principle (MP). In the present paper, a dynamic programming (DP) principle is presented for a special class of BSDE-constrained stochastic optimal control problems. The principle is applied to derive the solution of the nonlinear filtering problem.

Additional file 1.

Additional file 1: Figure S1. FT-IR spectra of (1) DS and (2) DS-Ce6. Figure S2. a Representative confocal microscopic images and quantification of dose-dependent cellular uptake of DS-Ce6 in the activated macrophages. *P

Game streaming technology allows users to play games by connecting to the cloud without separate installation and to play various games on any device, providing a convenient gaming environment for the user. As the 5G environment has been recently established, slow data transmission and reception speeds, which were disadvantages of game streaming, have been accelerated, and as a result, game streaming services are being actively provided. In this paper, we designed a game platform that would become the basis of the development of game streaming platform and implemented it using Android Studio.

The aim of this study was to investigate the optimal conditions for increasing the growth yield of Bacillus subtilis SRCM102046, a strain possessing potential biopreservative properties. B. subtilis SRCM102046 showed remarkable antibacterial activity against a wide range of bacterial foodborne pathogens that cause serious food spoilage, as well as high antioxidant capacity. Response-surface methodology (RSM) was used to optimize medium composition to enhance B. subtilis SRCM102046 biomass. The effects of 14 different components on biomass production were investigated and three significant positive factors, molasses, sucrose, and peptone, were selected as the main factors for improving biomass based on a Plackett-Burman design (PBD). Next, we optimized the concentrations of these three factors using a central composite design. The predicted optimized concentrations were 7 g/L molasses, 7 g/L sucrose, and 2 g/L peptone. The coefficient of determination (R2, 0.9755) for the model and probability value showed that our model was highly significant. Finally, an overall approximate 9-fold increase in dry cell weight yield (22.03 g/L) was achieved using the optimized medium compared with the non-optimized medium (2.47 g/L). Furthermore, we confirmed that the antibacterial activity and antioxidant activity also increased by 140% and 100.41%, respectively. These research is expected to be useful data for the production of food preservatives by establishing optimal conditions for increasing the growth yield of microorganisms possessing excellent antimicrobial activity.

In this study, we tried to screen the Bacillus strain having safety probability by isolation of strains from traditional fermented food, measurement of probiotic properties, and the fermentative characteristics of Cheonggukjang. We isolated 400 Bacillus-like isolates from traditional fermented foods. Selected strains examined on the prevalent characteristic such as extracellular enzyme and antibacterial activities, and their safety probability was confirmed by biogenic amine productivity, hemolytic, and harmful substances and enzyme productivity. We selected the 5 strains by analysis of biogenic amine, antibacterial and B. cereus toxic associated gene. Five selected strains were examined on cell surface hydrophobicity, and bile and acid tolerance, and we selected the SRCM100730 as the final strain. SRCM100730 was confirmed B. amyloliquefaciens by 16S rRNA sequencing, and named the B. amyloloquefaciens SRCM100730 (KCCM11966P). Finally, we manufactured Cheonggukjang using SRCM100730 for confirmation of fermentation properties. Manufactured Cheonggukjang did not contain B. cereus, and showed that γ-PGA and extracellular enzyme activities were superior to commercial Chunggukjang. Amino nitrogen content was 544.02 mg% and 26 free amino acid were detected, and the bitterness-related amino acid content was lower than commercial Cheonggukjang. Especially, the amount of GABA was 3 fold higher than commercial Cheonggukjang. These results suggest that SRCM100730 have high availability in commercial probiotics market and fermented food industry.

본 연구는 최근 가족이 함께하는 활동으로서 주목받고 있는 가족식사활동의 빈도, 식생활 가사노동 분담수준, 가족식사활동에 대한 가족의례적 의미부여, 가족의사소통 등의 측면을 살펴보고, 이 변수들 과 기혼여성의 가정생활만족도와의 관계를 분석함으로써 실천적 함의를 제공하는 데 목적이 있다. 이를 위해 서울·경기 지역의 초등학생 자녀를 둔 기혼여성 318명에 대한 설문조사 자료를 토대로 중다 회귀분석 및 상호작용 효과 분석을 실시하였다. 주요 결과는 다음과 같다. 첫째, 가족내식의 빈도, 식 생활 가사노동 분담수준, 가족식사활동에 대한 가족의례적 의미부여 정도는 가정생활만족도에 통계적으로 의미 있는 정적(+) 영향을 미치는 것으로 나타났다. 둘째, 가정생활만족도에 영향을 미치는 가족 내식의 빈도와 가족의사소통 유형의 상호작용 효과는 통계적으로 의미가 있었다. 구체적으로 가족의사 소통 유형이 순기능적일 때, 가족내식 빈도가 증가할수록 기혼여성의 가정생활만족도는 높게 나타났다. 이러한 결과를 바탕으로 본 연구의 함의와 제언이 제시되었다.

The possibility of using hyphomycete fungi as suitable biocontrol agents against greenhouse whitefly has led to the isolation of various insect pathogenic fungi. Among them is Beauveria bassiana, one of the most studied entomopathogenic fungi. The objective of this study was to use B. bassiana M130 as an insecticidal agent against the greenhouse whitefly. M130 isolated from infected insects is known to be a biocontrol agent against greenhouse whitefly. Phylogenetic classification of M130 was determined according to its morphological features and 18S rRNA sequence analysis. M130 was identified as B. bassiana M130 and showed chitinase (342.28 units/ml) and protease (461.70 units/ml) activities, which were involved in the invasion of the host through the outer cuticle layer, thus killing them. The insecticidal activity was 55.2% in petri-dish test, 84.6% in pot test, and 45.3% in field test. The results of this study indicate that B. bassiana has potential as a biological agent for the control of greenhouse whitefly to replace chemical pesticides.

The greenhouse whitefly, Bemisia tabaci, is considered one of the most destructive pests of crops. In this study, we aimed to determine the optimal liquid culture conditions in shake flasks for maximal sporulation of Beauveria bassiana M130 using rice bran. The optimal initial pH for the spore production of B. bassiana using extracted rice bran medium was 5.2 and . The screening in shake flasks of carbon and nitrogen sources resulted in the identification of an optimal medium based on 0.5% , with extracted rice bran 8:1. Using this medium, a production level of spores per ml was obtained after six days from culture inoculation at in a rotary shaking incubator at 130 rpm. In addition, the specific activities of extracellular enzymes of chitinase and protease were and , respectively. These results suggest that Beauveria bassiana M130 could be a bio-controller for the greenhouse whitefly.

This paper shows that the OFDM(Orthogonal Frequency Division Multiplex) system is robust to multipath than CDMA (Code Division Multiple Access) system and it has a strong possibility to be utilized as a supplementing wireless location system for the forthcoming portable internet network. The OFDM system based on IEEE 802.16e is a wireless TDD (Time Division Duplex) OFDMA (Orthogonal Frequency Division Multiple Access) system providing portable internet services in 2.3 GHz frequency band and is scheduled in service in Korea starting in 2006. In this paper, multipath error is calculated using a two-ray model and compared with that of a CDMA system which is following IS-95. The OFDM system shows a maximum multipath error of 3 m while a CDMA system shows a maximum multipath error of 61 m. For this simulation, an early-late technique is used. This technique is usually used to match synchronization of signal in DLL(Delay Lock Loop).

The global ultrasonic system for the self-localization of a mobile robot consists of several ultrasonic transmitters fixed at some reference positions in the global coordinates of robot environment. By activating the ultrasonic transmitters, the mobile robot is able to get the distance to the ultrasonic transmitters and compute its own position in the global coordinate. Due to the limitation on the ultrasonic signal strength and beam width as well as the environmental obstacles however, the ultrasonic signals from some generator may not be transmitted to the robot. Thus, instead of activating the all ultrasonic transmitters, it is necessary to select some ultrasonic generators to activate based on the current robot position. In this paper, we propose a selective activation algorithm for self-localization with the global ultrasonic system. The selective activation algorithm gets the meaningful ultrasonic data at every sampling instants, which results in the faster and more accurate response of the self-localization than the conventional sequential activation. Through the self-localization and path following control, we verify the effectiveness of the proposed selective activation algorithm.

Variability in rapid response system (RRS) characteristics based on the admitted wards is unknown. We aimed to compare differences in the clinical characteristics of RRS activation between patients admitted to medical versus surgical services. We reviewed patients admitted to the hospital who were detected by the RRS from October 2012 to February 2014 at a tertiary care academic hospital. We compared the triggers for RRS activation, interventions performed, and outcomes of the 2 patient groups. The RRS was activated for 460 patients, and the activation rate was almost 2.3 times higher for surgical services than that for medical services (70% vs. 30%). The triggers for RRS activation significantly differed between patient groups (P = 0.001). They included abnormal values for the respiratory rate (23.2%) and blood gas analysis (20.3%), and low blood pressure (18.8%) in the medical group; and low blood pressure (32.0%), low oxygen saturation (20.8%), and an abnormal heart rate (17.7%) in the surgical group. Patients were more likely classified as do not resuscitate or required intensive care unit admission in the medical group compared to those in the surgical group (65.3% vs. 54.7%, P = 0.045). In multivariate analysis, whether the patient belongs to medical services was found to be an independent predictor of mortality after adjusting for the modified early warning score, Charlson comorbidity index, and intervention performed by the RRS team. Our data suggest that RRS triggers, interventions, and outcomes greatly differ between patient groups. Further research is needed to evaluate the efficacy of an RRS approach tailored to specific patient groups., Graphical Abstract