Spatial Performance Analysis and Design Principles for Wireless Peer Discovery

In wireless peer-to-peer networks that serve various proximity-based applications, peer discovery is the key to identifying other peers with which a peer can communicate and an understanding of its performance is fundamental to the design of an efficient discovery operation. This paper analyzes the performance of wireless peer discovery through comprehensively considering the wireless channel, spatial distribution of peers, and discovery operation parameters. The average numbers of successfully discovered peers are expressed in closed forms for two widely used channel models, i.e., the interference limited Nakagami-m fading model and the Rayleigh fading model with nonzero noise, when peers are spatially distributed according to a homogeneous Poisson point process. These insightful expressions lead to the design principles for the key operation parameters including the transmission probability, required amount of wireless resources, level of modulation and coding scheme (MCS), and transmit power. Furthermore, the impact of shadowing on the spatial performance and suggested design principles is evaluated using mathematical analysis and simulations.Comment: 12 pages (double columns), 10 figures, 1 table, to appear in the IEEE Transactions on Wireless Communication

Epidemic models for U.S. financial subprime mortgage crisis in 2008 influencing on Korean corporations

Department of Management EngineeringA financial crisis can spread like a contagious disease to both domestic sectors including demand market and foreign markets which are linked to one country with various aspects. This work mainly focuses on contagious phenomenon which is observed in Korean corporations enlisted in KOSPI & KOSDAQ index right after U.S financial shock in 2008. To set up the model, we use SIR epidemic model to detect epidemic dynamics in Korean corporations after shock. In addition, EDF model is also applied to analyze the degree of contagion within individual business. Using corporate fundamental data from KRX and FSS, including stock price, total market value, and current liabilities from Jun. 2008 to Jun. 2010, we observe contagious features resulted from U.S. financial crisis - EDFs are rising or show sustained level within infected corporations. We also presume parameters including contact rate and recovery rate to identify epidemic model of U.S. financial crisis which especially affected business sector in Korea. Further research is needed to identify the individual movement of certain sector or individual corporations from a view of agent-based model.ope

Writing Sample

Includes Eel Stew

Group Based Trajectories Of Blood Pressure Components From Adulthood To Elderly In Chinese Workers

Objective: The study aimed to identify trajectories of systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure (PP) in Chinese adult workers from ages 18 to 81 years. Methods: Analysis was conducted with a longitudinal data from Qingdao Port Health and Nutrition Examination Survey. This is a prospective study of employees of China\u27s Qingdao Port Company that was initiated in 1999 and has been collecting annual measure of blood pressure. For our analysis, we focused on the cohort from 2000 to 2011. A group-based trajectory modeling was adopted to identify patterns of blood pressure over the lifespan. The dual model was used to jointly estimate the trajectories of two distinct, but related longitudinal outcome series. Results: Five trajectory patterns were identified from dual trajectory model of systolic blood pressure and pulse pressure, and diastolic blood pressure and pulse pressure. Systolic blood pressure kept increasing over time whereas diastolic blood pressure gradually increased then decreased in older ages. Pulse pressure began to increase in middle age and rose more steeply subsequently. In the dual model, the posterior probability of being assigned to a distinct group for one outcome was influenced by the membership in the group of the other outcome that was modeled simultaneously. The most interesting finding was that the group membership assignment in single trajectory model remained the same in dual trajectory model only for systolic blood pressure. Conclusion: Classifying individuals into unobserved latent trajectory groups allow us to gain a better understanding of the determinants of blood pressure patterns and lead to more personalized treatment and prevention plans among Chinese adult workers

Revisiting Multiplication Area Models for Whole Numbers

We argue that there are two conceptually different area models for whole number multiplication: area-to-area model and lengths-to-area model depending on how multiplication operation is conceived: action on / change of an initial quantity, or operation / coordination of two quantities. These models complement each other to promote students’ conceptual understanding of whole number multiplication and help students extend their understanding of whole number multiplication to fraction multiplication

Revisiting Multiplication Area Models for Whole Numbers

We argue that there are two conceptually different area models for whole number multiplication: area-to-area model and lengths-to-area model depending on how multiplication operation is conceived: action on / change of an initial quantity, or operation / coordination of two quantities. These models complement each other to promote students’ conceptual understanding of whole number multiplication and help students extend their understanding of whole number multiplication to fraction multiplication