A new architecture for a mobile ad-hoc communication network is developed, and simulation results show that the proposed MAC protocol can enhance transmission success probability from 0 to 97%. Two novel applications of vehicle-to-vehicle networks are then developed and simulated. The first application is a \Cooperative Adaptive Cruise Con- trol" which uses communicated information to improve on ordinary cruise control systems. Communicating a \virtual brake light" between vehicles is shown to decrease the accelerations required to maintain safe following distances in cut-in and hard braking situations. The second application is a \Cooperative Estimation" algorithm. The idea behind this algorithm is that each vehicle on the road is potentially a driving condition \sensor." By combining data communicated from many vehicles on the roadway, the cooperative estimation algorithm is able to produce estimates of driving time and road condition that are significantly better than those that any one vehicle could produce on its own. While developing the cooperative road condition estimation algorithm, it is found that the problem's crux is at the vehicle level, so the friction estimation problem is then investigated at a vehicle/tire level through exten- sive experimentation. An exciting new type of \slip-based" road condition estimator is developed and experimentally shown to be able to distinguish between wet and dry roads using no dedicated road condition sensors sen- sors. In-depth literature review complements our own results and shows that \slip-based" estimators of the type developed may be very useful to help solve the AHS road condition estimation problem.

Apolipoprotein (apo) E4 is a risk factor for heart disease, Alzheimer's disease, and other forms of neurodegeneration, but the underlying mechanisms are unknown. Domain interaction, a structural property that distinguishes apoE4 from apoE2 and apoE3, results in more rapid turnover and lower plasma levels of apoE4. To determine whether domain interaction affects brain apoE levels, we analyzed brain homogenates from human apoE3 and apoE4 knock-in mice, wild-type mice, and Arg-61 apoE mice, in which domain interaction was introduced by gene targeting. As determined on Western blots, the hemibrain, cortex, hippocampus, and cerebellum of knock-in mice had 30 - 40% lower levels of apoE4 than apoE3, and Arg-61 mice had 25 - 50% lower apoE levels than wild-type mice. In the CSF, Arg-61 apoE level was 40% lower than the wild-type level. Arg-61 apoEmRNA levels were similar to or slightly higher than wild-type apoEmRNA levels. Thus, the lower Arg-61 apoE levels were not attributable to decreased mRNA levels. In culture medium from heterozygous Arg-61/wild-type and apoE4/apoE3 primary astrocytes, Arg-61 apoE and apoE4 levels were lower than wild-type apoE and apoE3, respectively, suggesting that primary astrocytes secrete lower amounts of Arg-61 apoE and apoE4. These results demonstrate that domain interaction is responsible for the lower levels of both human apoE4 and mouse Arg-61 apoE in mouse brain. Cells may recognize apoE4 and Arg-61 apoE as misfolded proteins and target them for degradation or accumulation. Thus, degradation/accumulation or lower levels of apoE4 may contribute to the association of apoE4 with Alzheimer's disease.

We comparatively assess the influence of adaptive cruise control (ACC) and cooperative adaptive cruise control (CACC) systems on highway traffic behaviors. The primary goal is to study the design and implementation of vehicle-vehicle/roadside-vehicle communication, which enhances an ACC system to a CACC one. In addition, the impact of market penetration of ACC/CACC vehicles and controller aggression are also evaluated. Two simulation works are presented. The microscopic work simulates a single ACC/CACC vehicle using MATLAB/SIMULINK. A cut-in scenario and a braking scenario are tested. Vehicle-vehicle communication saves control effort in the former scenario, while shows little effect in the latter. In the macroscopic work we simulate ACC/CACC controlled highway merging with SHIFT language. The results show beneficial effects of communication in terms of braking effort, average velocity, waiting-to-merge queue length, and main lane traffic shock wave caused by merging. The higher the market penetration of controlled vehicles the better the system performs. The aggressiveness of controller has mixed influence, which provides a tradeoff between efficiency and safety. We study the wireless communication among highway vehicles. A vehicle- vehicle Location-Based Broadcast (LBB) communication protocol is designed to meet highway safety applications' communication requirements. The analytical expressions of the performance of the protocol in terms of probability of transmission failure and channel occupancy are derived with commonly satisfied assumptions. The optimal relation between the performance and design parameters is obtained from the expressions. The sensitivity of the protocol performance is tested for various communication conditions as well as highway traffic conditions. Feasible combinations of the communication and highway traffic parameters are found for certain requirements on protocol performance. The analysis is conducted in accordance to the communication condition in the newly-assigned 5.9 GHz Dedicated Short Range Communication (DSRC) spectrum. More experiments are done to find out the factors that influence the slip measurements in order to refine our results of friction coefficient estimation. To obtain the circumferential velocity of the wheel, the exact tire radius is needed. The change in the spring constant based on tire air pressure is obtained, and also the increase in tire radius due to the faster velocity is considered. The normal force applied on each wheel due to the vehicle pitch motion resulting from acceleration and deceleration is also estimated using static vehicle model. Brake torque sensor and accelerometer are used to find the normal force. Using the estimated normal force and road force, the tire-road friction coefficient is obtained. The characteristics of the friction coefficient and slip curve are studied on different road conditions with the refined slip measurements. An originally proposed slip-based controller does not seem to work very well in an practical situation due to actuator time delay. However, experimental results show that the existing nonlinear controller with the limited slip assumption shows good performance even in an emergency braking situation. Therefore, instead of using different control algorithm, this research focuses on the control strategies dedicated to emergency situation for the platoon. In order to integrate the benefits from the communication and friction coefficient estimation technique, a safe control strategy is considered in the situation when the platoon of vehicles needs to decelerate rapidly. It is assumed that we have the knowledge of friction coefficients between road and tire and our vehicles are equipped with proper communication methods. Then, the theoretical bounds for the reference trajectory accelerations are calculated that do not cause the actuator saturation using linear vehicle and controller model.

In fiscal year 2002/2003 we finished the study of the effect of vehicle-vehicle/vehicle-roadside communication on the performance of adaptive cruise control (ACC) systems. Two simulation studies were finished. The first is a single ACC vehicle simulation using MATLAB/SIMULINK. A cut-in scenario and a braking scenario are tested. Communication greatly saves control effort in the former scenario, while it has little effect in the latter. The other work simulates ACC controlled highway merging using SHIFT language. The results show the beneficial effects of communication in terms of the braking effort, the waiting-to-merge queue length, and the main lane traffic shock wave caused by merging.