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Workers in construction and transportation sectors are at increased risk for work-related injuries and fatalities by nearby traffic. Barricade-mounted warning lights meeting current specifications do not always provide consistent and adequate visual guidance to drivers and can contribute to glare and reduced safety. Through an implementation of sensors and wireless communications, a novel, intelligent set of warning lights and a tablet-based interface were developed. The lights modulate between 100% and 10% of maximum intensity rather than between 100% and off in order to improve visual guidance and adjust their overall intensity based on ambient conditions. The lights can be synchronized or operated in sequential flash patterns at any frequency between 1 and 4 Hz, and sequential patterns automatically update based on global positioning satellite (GPS) locations displayed in the control interface.

Present standards for vehicle forward lighting specify two headlamp beam patterns: a low beam when driving in the presence of other nearby vehicles, and a high beam when there is not a concern for producing glare to other drivers. Adaptive lighting technologies such as curve lighting systems with steerable headlamps may be related to increments in safety according to the Insurance Institute for Highway Safety, but isolating the effects of lighting is difficult. Recent analyses suggest that visibility improvements from adaptive curve lighting systems might reduce nighttime crashes along curves by 2%-3%. More advanced systems such as adaptive high-beam systems that reduce high-beam headlamp intensity toward oncoming drivers are not presently allowed in the U.S. The purpose of the present study is to analyze visual performance benefits and quantify potential safety benefits from adaptive high-beam headlamp systems.

This paper presents a method to reduce common-mode (CM) electromagnetic interference (EMI) emission from electric actuators powered from PWM rectifier-inverter drives for use on more electric aircraft. An EMI model is presented first from which a simplified system CM model is developed to serve as the basis for the analysis and the development of effective CM EMI reduction methods. The proposed method is to insert a high-impedance element in series with the CM EMI voltage source, and create a low-impedance path in parallel with the high-impedance element to bypass the CM current. The method effectively reduces the amplitude of the CM voltage that drives the input and output CM current such that less filtering would be required. Experimental results from a laboratory motor drive system are presented to verify the effects of the proposed method.

The performance enhancement of a vertical tail provided by aerodynamic flow control could allow for the size of the tail to be reduced while maintaining similar control authority. Decreasing tail size would create a reduction in weight, drag, and fuel costs of the airplane. The application of synthetic jet actuators on improving the performance of the vertical tail was investigated by conducting experiments on 1/9th and 1/19th scale wind tunnel models (relative to a Boeing 767 tail) at Reynolds numbers of 700,000 and 350,000, respectively. Finite-span synthetic jets were placed slightly upstream of the rudder hinge-line in an attempt to reduce or even eliminate the flow separation that commences over the rudder when it was deflected to high angles. Global force measurements on the 1/9th scale model showed that the flow control is capable of increasing side force by a maximum of 0.11 (19%). The momentum coefficient that created this change was relatively small (Cμ = 0.124%).

The purpose of this paper is to quantitatively compare the efficiency, of silicon and silicon carbide power devices in power circuit environments. Models developed for the MOSFET, PiN rectifier, Schottky rectifier, for both silicon and silicon carbide will be presented. These models have been implemented in the SABER circuit simulator and used to simulate power circuits, in order to determine the efficiency of the silicon and silicon carbide devices. It is essential for a fair comparison that the two devices are optimally designed, hence optimization of area has been performed and an analytical expression, for the optimum area as a function of operating conditions, determined. The efficiency for the optimum silicon and silicon carbide devices as a function of frequency, blocking voltages and operating currents is then presented. It has been shown that the 5000V SiC MOSFET has efficiencies comparable to the 300V Si counterpart.

This paper presents modeling and analysis of the harmonic performance of multi-pulse Transformer-Rectifier Units (TRU) and Autotransformer-Rectifier Units (ATRU) under different non-ideal operation conditions. Other than numerical simulations, the paper presents an analytical method to quantify and study the effects by describing the operation of the converters by the so-called mapping functions. Double-Fourier series method is applied to determine the Fourier representation of the mapping functions. Based on the analytical models in the frequency domain, the effects of harmonic voltage and load current harmonics are theoretically investigated.

Taking advantage of growing consumer interest in light emitting diode (LED) headlights, an increasing number of after-market LED replacement bulbs is available on the market. They are designed to have similar socket shapes and sizes as halogen bulbs, in order to fit into existing headlight housings. Although none of these LED replacement bulbs conform to present federal headlighting regulations, and some are labeled for "off road use" only, others claim to meet current regulations. Regardless, many different LED bulbs can be easily purchased and installed by vehicle owners, who may or may not be aware of their regulatory status. Several different LED replacement bulb kits, each designed to replace a conventional 55-W H11 halogen bulb, were purchased and tested in three different low-beam headlight units.

This paper examines the consequences of fabrication effects on the performance of injection molded plastic light pipes for distributive automotive lighting. It discusses the magnitude of these effects on propagating and output light. Molding errors, such as sinks, voids, flow lines, knit lines, and warpage, will be examined through computer modeling and measurement of sample distributive lighting systems. Two example light pipe systems will be presented, an instrument cluster pointer system and a regional distributive interior lighting system. For the pointer system, computer modeling results, such as total light output and output exitance distributions will be presented. Modeling results will be presented for both an error free system and system that include the aforementioned molding errors. These results will be compared to determine the output light loss and redistribution.

Vehicle headlamps are essential for driver safety at night, and technological evolution of headlamps over several decades has brought substantial improvements to driver visibility and comfort. Nonetheless, glare remains an important concern among many in the driving public, perhaps even more so in North America, where requirements for headlamps differ from those in much of the rest of the world. In most of the world, headlamps producing higher luminous flux are required to have automatic leveling and cleaning systems, thought to help reduce glare. The arrival of headlamp systems in the worldwide marketplace with luminous flux values just below those triggering requirements for leveling and cleaning systems will bring new questions about the causes of and countermeasures for glare.

Rear automotive lighting systems employing dynamic features such as sweeping or flashing are not commonly used on vehicles in North America, in part because they are not clearly addressed in vehicle lighting regulations. Nor is there abundant evidence suggesting they have a substantial role to play in driver safety. The results of a human factors investigation of the potential impacts of dynamic rear lighting systems on driver responses are summarized and discussed in the context of safety, visual effectiveness and the present regulatory context.

Flashing emergency lights on police cars, fire trucks, and ambulances need to be bright enough to alert otherwise unaware drivers about their presence on and near the roadway. Anecdotal evidence suggests that public safety agencies select emergency lighting systems with red or blue flashing lights based on their apparent brightness, with brighter lights judged as "better." With the advent of light emitting diodes (LEDs), emergency flashing lights are brighter and produce more highly saturated colors, thereby causing greater discomfort and disability glare. As a result, first response workers are at higher risk for being injured or killed in vehicle crashes because approaching drivers cannot see them. In the present study, participants viewed red and blue flashing lights on a scale model police vehicle, conforming to present recommended practices for emergency lights. Lights varied in intensity and optical power (intensity × duration).

The advent of light-emitting diode (LED) technology for automotive lighting allows flexibility of the spectral distribution of forward headlighting systems, while meeting current requirements for “white” illumination. As vehicle headlights have become whiter (with more short-wavelength light output) over the past several decades, their potential impacts on visual discomfort for oncoming and preceding drivers have been hotly debated. It is known that a greater proportion of short-wavelength energy increases discomfort glare, and that increasing the background light level (e.g., through roadway lighting) will decrease perceptions of discomfort. More recently it has been demonstrated that the visual system exhibits enhanced short-wavelength sensitivity for perceptions of scene brightness.

Vehicle forward lighting can use a multiplicity of light sources each varying in their spectral characteristics. Present standards for low beam headlight performance also allow variability in the peak intensities that drivers can be exposed to, as well as the durations of those exposures. Previous research has led to mixed results regarding whether the spectral distribution of a headlight source influences the length of time the visual system needs to recover the ability to see objects that might present hazards along the roadway. One recent study showed that the integrated light dose (intensity × duration) but not the spectral distribution impacted recovery times for targets presented in a constant, known location, where they would be viewed with the fovea. An experiment was carried out to assess whether the spectral distribution of a glare source might differentially impact one's ability to see a target using peripheral vision when the location of the target is not known.

Headlight glare is a major concern of the driving public. In the past couple of years there have been concerns expressed about the use of light emitting diode (LED) lighting technologies and possible impacts LEDs may have on people, including circadian disruption, retinal hazards, and glare. Under typical use cases, vehicle headlight exposures are insufficient to cause circadian disruption or retinal damage, but can result in disability and discomfort glare, as well as glare recovery. In general, white LEDs used for illumination have greater short-wavelength content than halogen lamps used in many headlights, and short wavelengths have been implicated in visual discomfort from bright lights at night. Previous literature is inconsistent regarding whether the spectral (color) content of a glare source affects the amount of recovery time needed to see objects, following exposure to a bright light such as a vehicle headlight.

Recent naturalistic driving studies provide a useful means for gathering information about the potential role of lighting in driving safety. The Naturalistic Driving Study carried out through the Strategic Highway Research Program 2 (SHRP2) includes real-time driving data for crashes, near-crashes and baseline driving events for more than 3000 drivers across the United States. Among the data collected are oncoming illuminance recordings that can be used to estimate glare exposure for the drivers in the study. Data for crash events occurring at night were compared to those for baseline driving under similar conditions and by drivers of similar ages. The resulting light exposure data indicate that oncoming glare is likely to be only a very small factor associated with nighttime crashes, but that the influence of glare may increase for older drivers.

Transportation safety agencies are working to consider how to best incorporate the potential safety benefits of intelligent vehicle lighting systems such as adaptive driving beam headlights and other systems on vehicles used by the general public. As these deliberations continue, additional data on the impacts of lighting technological developments are important to generate and share. An analytical study was performed to assess how different vehicle lighting configurations including ADB and other technologies can assist drivers in achieving visual acquisition of potential hazards along the road. The investigation also compared drivers varying in age and whose visual performance differs because of optical changes in the visual system. The importance of considering visibility for older drivers is critical because this group is an increasingly large proportion of the overall driving population.

Discomfort glare from vehicle lighting is more difficult to measure precisely than disability glare, but may have important implications for driver behavior, and in turn on driving safety. Many studies of discomfort glare have found that, as with disability glare, the illuminance at the eyes from a bright light is the primary determinant of the sensation of glare. Nonetheless, the luminance of a light source also can influence discomfort glare, especially when the source is close enough to subtend a relatively large visual angle on the order of a third of a degree or larger. In addition, interactions with the absolute illuminance from a light source are not well understood. The results of an experimental investigation of discomfort glare in terms of light source illuminance, luminance and size are presented and discussed along with implications for automotive lighting applications.

Nighttime driving cannot be accomplished without vehicle headlighting. A growing body of evidence demonstrates the role of lighting on visual performance and in turn on nightttime driving safety in terms of crashes. Indirect impacts of lighting via comfort or other factors are less well understood, however. A two-part field study using real-world drivers of an instrumented vehicle was conducted to assess the potential role of oncoming headlight glare as a factor in driving behaviors that might be related to increased crash risks. In the first part of the study, drivers' behaviors when navigating through roadway intersections having different levels of crash risk were recorded in order to identify responses that were correlated with the risk level. In the second part, drivers were exposed to different levels of glare from oncoming headlights; several of the same risk-related behaviors identified in the first part of the study were exhibited.

Photometric performance specifications for vehicle headlamp specifications in North America are given in terms of luminous intensity values at various angular locations with the objective of providing sufficient illumination for forward visibility while controlling for glare toward oncoming and preceding vehicle drivers. Abundant evidence suggests that luminous intensity is an appropriate metric for characterizing the degree to which a headlamp can produce disability glare through veiling luminances under a wide range of viewing conditions. Notwithstanding that discomfort glare exhibits a differential spectral sensitivity from the photopic luminous efficiency function used to characterize light, luminous intensity does not always predict discomfort glare. For example, the luminance of the luminous element(s) can be more predictive of discomfort when headlamps are viewed from relative close distances.

Aggressive use of microscopy and profilometry can expedite trouble shooting of a wide variety of friction/lubrication/surface quality problems. Recent research at Rensselaer has focused on physical modelling of the sheet stamping operation, in particular the binder-radius and draw bead regions. Friction models are examined in conjunction with workpiece surface quality and binder-radius tooling topography. The friction coefficient remains stable throughout a wide variety of test conditions. Area-of-contact measurements confirm the model, although appreciable scatter is noted. Profilometry measurements, taken from a variety of tooling finishes, demonstrate that alternative indices may correlate with friction better than the traditionally quoted Ra.