Kyunghan Lee

This paper presents a quantitative study on the performance of 3G mobile data offloading through WiFi networks. We recruited 97 iPhone users from metropolitan areas and collected statistics on their WiFi connectivity during a two-and-a-half-week period in February 2010. Our trace-driven simulation using the acquired whole-day traces indicates that WiFi already offloads about 65% of the total mobile data traffic and saves 55% of battery power without using any delayed transmission. If data transf

Simulating human mobility is important in mobile networks because many mobile devices are either attached to or controlled by humans and it is very hard to deploy real mobile networks whose size is controllably scalable for performance evaluation. Lately various measurement studies of human walk traces have discovered several significant statistical patterns of human mobility. Namely these include truncated power-law distributions of flights, pause-times and inter-contact times, fractal way-poin

This is a quantitative study on the performance of 3G mobile data offloading through WiFi networks. We recruited about 100 iPhone users from a metropolitan area and collected statistics on their WiFi connectivity during about a two and half week period in February 2010. We find that a user is in WiFi coverage for 70% of the time on average and the distributions of WiFi connection and disconnection times have a strong heavy-tail tendency with means around 2 hours and 40 minutes, respectively. Usi

Many empirical studies of human walks have reported that there exist fundamental statistical features commonly appearing in mobility traces taken in various mobility settings. These include: 1) heavy-tail flight and pause-time distributions; 2) heterogeneously bounded mobility areas of individuals; and 3) truncated power-law intercontact times. This paper reports two additional such features: a) The destinations of people (or we say waypoints) are dispersed in a self-similar manner; and b) peopl

This is by far the first paper considering joint optimization of link scheduling, routing and replication for disruption-tolerant networks (DTNs). The optimization problems for resource allocation in DTNs are typically solved using dynamic programming which requires knowledge of future events such as meeting schedules and durations. This paper defines a new notion of optimality for DTNs, called snapshot optimality where nodes are not clairvoyant, i.e., cannot look ahead into future events, and t

UNLABELLED: Small-animal PET has opened the way for imaging (18)F-FDG uptake in murine tumor models, but the need for anesthesia raises concern over its potential influence on (18)F-FDG kinetics. We thus investigated such effects on cultured cells and on tumor-bearing mice after short- and long-term fasting. METHODS: Lewis lung carcinoma (LLC) cells and cardiomyoblasts were treated for 2 h with a 100 micromol/L concentration of xylazine, ketamine, xylazine plus ketamine (Xy/Ke), or pentobarbital

This paper presents a quantitative study on the performance of 3G mobile data offloading through WiFi networks. We recruited about 100 iPhone users from metropolitan areas and collected statistics on their WiFi connectivity during about a two and half week period in February 2010. Our trace-driven simulation using the acquired traces indicates that WiFi already offloads about 65% of the total mobile data traffic and saves 55% of battery power without using any delayed transmission. If data trans

PURPOSE: We investigated the capacity of F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) to differentially diagnose immunoglobulin G4-related disease (IgG4-RD) in clinically suspected patients. MATERIALS AND METHODS: Subjects were 94 clinically suspected patients who had tissue IgG4 staining (n = 85) or serum IgG4 greater than 135 mg/dL (n = 9) and underwent FDG PET/CT within 40 days. Clinical, serologic, pathological, and PET/CT findings were analyzed.

To fully understand the glycolytic behavior of cancer cells, it is important to recognize how it is linked to pH dynamics. Here, we evaluated the acute effects of mild acidification and alkalization on cancer cell glucose uptake and glycolytic flux and investigated the role of hexokinase (HK). Cancer cells exposed to buffers with graded pH were measured for 18F-fluorodeoxyglucose (FDG) uptake, lactate production and HK activity. Subcellular localization of HK protein was assessed by western blot

PURPOSE: This study investigated 18F-FDG PET/CT features of adenovirus-vectored vaccination against COVID-19 in healthy subjects. PATIENTS AND METHODS: Thirty-one health care workers had been vaccinated Vaxzevria and underwent FDG PET/CT as an optional test for a cancer screening program. Size and FDG uptake of the hypermetabolic lymph nodes were measured. Uptake value of spleen was also measured with liver for comparison. RESULTS: All examinees who underwent FDG PET/CT within 14 days' interval

Breast cancers that express epidermal growth factor (EGF) receptors (EGFRs) are associated with poor prognosis. Our group recently showed in breast cancer patients that EGFR expression is strongly correlated with high tumor uptake of the glucose analogue, 18F-fluorodeoxyglucose (FDG). Here, we explored the cellular mechanism and signaling pathways that can explain the relation between EGFR and breast cancer cell glucose metabolism. FDG uptake, lactate production and hexokinase (HK) activity were