Pedestrian Dynamics: Modeling and Analyzing Cognitive Processes and Traffic Flows to Evaluate Facility Service Level

Walking is the oldest and foremost mode of transportation through history and the prevalence of walking has increased. Effective pedestrian model is crucial to evaluate pedestrian facility service level and to enhance pedestrian safety, performance, and satisfaction. The objectives of this study were to: (1) validate the efficacy of utilizing queueing network model, which predicts cognitive information processing time and task performance; (2) develop a generalized queueing network based cognitive information processing model that can be utilized and applied to construct pedestrian cognitive structure and estimate the reaction time with the first moment of service time distribution; (3) investigate pedestrian behavior through naturalistic and experimental observations to analyze the effects of environment settings and psychological factors in pedestrians; and (4) develop pedestrian level of service (LOS) metrics that are quick and practical to identify improvement points in pedestrian facility design. Two empirical and two analytical studies were conducted to address the research objectives. The first study investigated the efficacy of utilizing queueing network in modeling and predicting the cognitive information processing time. Motion capture system was utilized to collect detailed pedestrian movement. The predicted reaction time using queueing network was compared with the results from the empirical study to validate the performance of the model. No significant difference between model and empirical results was found with respect to mean reaction time. The second study endeavored to develop a generalized queueing network system so the task can be modeled with the approximated queueing network and its first moment of any service time distribution. There was no significant difference between empirical study results and the proposed model with respect to mean reaction time. Third study investigated methods to quantify pedestrian traffic behavior, and analyze physical and cognitive behavior from the real-world observation and field experiment. Footage from indoor and outdoor corridor was used to quantify pedestrian behavior. Effects of environmental setting and/or psychological factor on travel performance were tested. Finally, adhoc and tailor-made LOS metrics were presented for simple realistic service level assessments. The proposed methodologies were composed of space revision LOS, delay-based LOS, preferred walking speed-based LOS, and ‘blocking probability’

Experimental study of thermal conductivity reduction of silicon-germanium nanocomposite for thermoelastic application

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 67-70).To improve the thermoelectric energy conversion efficiency of silicon germanium (SiGe), two methods were used to decrease the thermal conductivity by increasing phonon boundary scattering at interfaces. In the first method, SiGe alloys were annealed at a temperature higher than the melting point to increase the number of grain boundaries. In the second method, SiGe composites were made with nanosize silicon particles. For annealed SiGe alloys thermal conductivity decreased by a factor of two while power factor remained the same value. For SiGe nanocomposite thermal conductivity decreased by a factor of four to that of bulk alloy, but electrical conductivity deteriorated. Future work will focus on increasing electrical conductivity while reducing the thermal conductivity.by Hohyun Lee.S.M

Thermoelectric properties of SiGe nanocomposites

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Page 164 blank.Includes bibliographical references.Direct energy conversion between thermal and electrical energy based on thermoelectric effects is attractive for potential applications in waste heat recovery and environmentally-friendly refrigeration. The energy conversion efficiency is related to the thermoelectric figure of merit ZT, which is proportional to the electrical conductivity, the square of the Seebeck coefficient, and the inverse of the thermal conductivity. Currently, the low ZT values of available materials restrict the large scale applications of this technology. Recently, however, significant enhancements in ZT were reported in nanostructured materials such as superlattices mainly due to their low thermal conductivities. According to the studies on heat transfer mechanisms in nanostructures, the reduced thermal conductivity of nanostructures is mainly attributed to the increased scattering of phonons at interfaces. Based on this idea, nanocomposites are also expected to have a lower thermal conductivity than their bulk counterparts of the same chemical configuration. Nanocomposites are materials with constituents of less than 100 nm in size. They can be fabricated with a low cost just by mixing nano sized particles followed by consolidation of nano sized powders. In this thesis, SiGe nanocomposites are investigated for power generation at high temperature. The material properties are characterized at different temperatures, and the optimized process conditions are explored experimentally. In addition, theoretical studies are carried out for better understanding of transport phenomena and our experimental results.(cont.) Grain boundaries in nanocomposites can scatter phonons, when their mean free paths are longer than the grain size. Mean free paths of electrons are usually shorter than the grain size of nanocomposites, so that the electrical conductivities of nanocomposites are not expected to change significantly. However, the experimental results show that nanostructures indeed affect electron transport. The grain boundary effects on electron transport are investigated to explain the experiments. Furthermore, the effects of nanosized pores are explored. Our experimental results show that pores in nanocomposites degrade the electrical conductivity more than predicted by effective medium theories. A scattering model is developed to understand the transport phenomena in porous materials. These modeling studies can also be used to guide sample preparation conditions.by Hohyun Lee.Ph.D

Oncology trainee perceptions of the prior authorization process: A national survey

Purpose: The medical trainee perspective regarding the prior authorization process has not been previously assessed. Here we evaluate the perceptions of radiation and medical oncology trainees regarding the prior authorization process and its effect on their training and patient care. Methods and Materials: A 12-question, nonincentivized, electronic national survey of radiation and medical oncology trainees at all Accreditation Council for Graduate Medical Education accredited oncology programs was conducted. Participation, perspectives, and experiences with the prior authorization process were assessed by Likert scale, free response, and multiple response selection. Results: Between January and March of 2019, the survey was distributed to 1505 trainees at 76 institutions with responses from 174/616 radiation (28.2%) and 139/889 medical oncology trainees (15.6%). The majority (69.2%) reported participating in the prior authorization process (radiation: 78.2% vs medical: 57.6%; Conclusions: These data indicate that trainees in US oncology programs are active participants in the prior authorization process and report that prior authorization approvals negatively influence their medical training and the quality of patient care. Additional efforts to revise the insurance approval process are warranted

Herbal Extracts That Reduce Ocular Oxidative Stress May Enhance Attentive Performance in Humans

We used herbal extracts in this study to investigate the effects of blue-light-induced oxidative stress on subjects’ attentive performance, which is also associated with work performance. We employed an attention network test (ANT) to measure the subjects’ work performance indirectly and used herbal extracts to reduce ocular oxidative stress. Thirty-two subjects participated in either an experimental group (wearing glasses containing herbal extracts) or a control group (wearing glasses without herbal extracts). During the ANT experiment, we collected electroencephalography (EEG) and electrooculography (EOG) data and measured button responses. In addition, electrocardiogram (ECG) data were collected before and after the experiments. The EOG results showed that the experimental group exhibited a reduced number of eye blinks per second during the experiment and faster button responses with a smaller variation than did the control group; this group also showed relatively more sustained tension in their ECG results. In the EEG analysis, the experimental group had significantly greater cognitive processing, with larger P300 and parietal 2–6 Hz activity, an orienting effect with neural processing of frontal area, high beta activity in the occipital area, and an alpha and beta recovery process after the button response. We concluded that reducing blue-light-induced oxidative stress with herbal extracts may be associated with reducing the number of eye blinks and enhancing attentive performance

Assessment of the Suitability of Trauma Triage According to Physiological Criteria in Korea

Purpose A trauma center project for treating patients with trauma has been established in Korea. A trauma team is activated based on the Centers for Disease Control and Prevention (CDC) field triage Step 1 for patient triage. Here, we determined if the currently applied criteria were appropriate for the triage of patients with trauma in Korea. Methods This retrospective study included patients who were taken to the regional trauma center from January 1, 2016 to December 31, 2019, and were registered in the Korean Trauma database. The rates for undertriage and overtriage were calculated from the in-field and in-hospital triage according to the CDC guidelines Step 1. Results Among the 9,383 patients transferred to the trauma center, 3,423 were directly transferred from the site and were investigated. The overall rates for undertriage and overtriage of these patients were 28.13% and 30.35%, respectively. For the patients who received in-field triage and were directly transferred to the trauma center, the rates for undertriage and overtriage were 27.92% and 32.39%, and 25.92% and 29.11% for in-hospital triage, respectively. The concordance rate of triage was 87.09%. Conclusion The current use of in-hospital triage physiological criteria as set out in the CDC guidelines Step 1, indicated an undertriage rate which was high and an overtriage rate within the acceptable range. Further studies on triaging patients with trauma are warranted. Improvements in the guidelines of the trauma center project are necessary and this needs to be supported by resources and training for field personnel

Capacitance-voltage characteristics of Pt/hBN/WSe2 metal-insulator-semiconductor capacitor doped by charge-transfer process

Metal-insulator-semiconductor (MIS) capacitors composed of low-dimensional van der Waals (vdW) materials are of fundamental interest for understanding carrier transport properties at the atomic scale. Herein, we fabricated a Pt/hBN/WSe2 MIS low-dimensional capacitor, followed by UV/ozone-induced oxidation to form a WOX layer, which is an electron-withdrawing agent. Capacitance-voltage (C-V) characteristics before and after p-doping of the WSe2 layer were compared for different durations of UV/ozone treatments. The C-V behaviors in the pristine condition exhibited ambipolar transport characteristics at both high and low frequencies because of co-existence of electron and hole carriers, which are advantageous for next-generation complementary MIS architectures. When WSe2 was p-doped, a typical p-type C-V curve with a high-frequency inversion region was observed, because the minority carriers (electrons) were unavailable. The frequency dispersions and ratios of the current to pristine hole concentrations as well as holes to electrons at different p-doping concentrations were analyzed. Finally, the controllability of the charge-transfer doping method was confirmed by chemically removing the WOX layer. The understanding of controllable and damage-free doping mechanisms in ambipolar vdW semiconductors is expected to help enhance electronic device performances at the atomic thickness. Published under an exclusive license by AIP Publishing.N