The volume of highway traffic in the United States continues to increase. In the face of this there is a concomitant need to improve and repair transportation infrastructure. Construction frequently requires a reducti...The volume of highway traffic in the United States continues to increase. In the face of this there is a concomitant need to improve and repair transportation infrastructure. Construction frequently requires a reduction in capacity during construction activity; consequently road users as well as adjacent businesses must endure the delays and inconveniences associated with transportation construction. Recognizing the problems that construction can produce, state highway agencies （SHAs） have continually sought ways to minimize the negative impact from their construction operations. Incentive contracting has played an important role in this effort to improve project performance. The Florida Department of Transportation （FDOT） is one of the leading SHAs using such innovative contracting methods as Incentive/Disincentive （I/D）, A＋B （cost plus time bidding） combined with I/D, No Excuse Bonus, and Liquidated Savings. This paper analyzes the traffic impact on incentive project time performance using highway construction projects recently completed in Florida. Project data obtained from FDOT were evaluated using time performance indices. A survey of traffic impact on project work types was performed in Florida in order to evaluate the relationship between construction project types and road traffic influence during construction. Based on the survey results, the 38 most frequently used work types in Florida during the study period were categorized into three traffic impact levels： （1） high traffic impact, （2） medium traffic impact, and （3） low traffic impact. Statistical analysis was performed. The results show that there are significant differences on project time performance between low and high impact levels as well as low and medium impact levels.展开更多
When an aircraft moves under a low carrier-to-noise ratio （CNR） or at a high speed, increasing the sensitivity of global navigation satellite system （GNSS） receiver is a goal quite hard to achieve. A novel acquisi...When an aircraft moves under a low carrier-to-noise ratio （CNR） or at a high speed, increasing the sensitivity of global navigation satellite system （GNSS） receiver is a goal quite hard to achieve. A novel acquisition scheme assisted with micro-electro-mechanical-sensor （MEMS） inertial navigation system （INS） is presented to estimate the Doppler caused by user dynamics relative to each satellite ahead of time. Based on tightly coupled GNSS/INS estimation algorithm, MEMS INS Doppler error that can be achieved is first described. Then, by analyzing the mean acquisition time and signal detection probability, the MEMS INS-assisted acquisition capabilities in cold, warm and hot starts are quantitatively determined and compared with the standard GNSS acquisition capability. The simulations and comparisons have shown that： the acquisition time in cold start can be shortened by at least 23 s, the time in warm start can be shortened to i s and the acquisition capability is improved 95%, and the reaequisition time in hot start can be shortened by around 0.090 s and the capability can be enhanced 40%. The results demonstrate the validity of the novel method.展开更多
文摘The volume of highway traffic in the United States continues to increase. In the face of this there is a concomitant need to improve and repair transportation infrastructure. Construction frequently requires a reduction in capacity during construction activity; consequently road users as well as adjacent businesses must endure the delays and inconveniences associated with transportation construction. Recognizing the problems that construction can produce, state highway agencies （SHAs） have continually sought ways to minimize the negative impact from their construction operations. Incentive contracting has played an important role in this effort to improve project performance. The Florida Department of Transportation （FDOT） is one of the leading SHAs using such innovative contracting methods as Incentive/Disincentive （I/D）, A＋B （cost plus time bidding） combined with I/D, No Excuse Bonus, and Liquidated Savings. This paper analyzes the traffic impact on incentive project time performance using highway construction projects recently completed in Florida. Project data obtained from FDOT were evaluated using time performance indices. A survey of traffic impact on project work types was performed in Florida in order to evaluate the relationship between construction project types and road traffic influence during construction. Based on the survey results, the 38 most frequently used work types in Florida during the study period were categorized into three traffic impact levels： （1） high traffic impact, （2） medium traffic impact, and （3） low traffic impact. Statistical analysis was performed. The results show that there are significant differences on project time performance between low and high impact levels as well as low and medium impact levels.
基金the National High Technology Research and Development Program (863) of China(No.2009AA12Z322)
文摘When an aircraft moves under a low carrier-to-noise ratio （CNR） or at a high speed, increasing the sensitivity of global navigation satellite system （GNSS） receiver is a goal quite hard to achieve. A novel acquisition scheme assisted with micro-electro-mechanical-sensor （MEMS） inertial navigation system （INS） is presented to estimate the Doppler caused by user dynamics relative to each satellite ahead of time. Based on tightly coupled GNSS/INS estimation algorithm, MEMS INS Doppler error that can be achieved is first described. Then, by analyzing the mean acquisition time and signal detection probability, the MEMS INS-assisted acquisition capabilities in cold, warm and hot starts are quantitatively determined and compared with the standard GNSS acquisition capability. The simulations and comparisons have shown that： the acquisition time in cold start can be shortened by at least 23 s, the time in warm start can be shortened to i s and the acquisition capability is improved 95%, and the reaequisition time in hot start can be shortened by around 0.090 s and the capability can be enhanced 40%. The results demonstrate the validity of the novel method.
