1,139 research outputs found
Employment-Based Health Insurance and Job Mobility: Is There Evidence ofJob-Lock?
No full textThis paper assesses the impact of employer-provided health insurance on job mobility by exploring the extent to which workers are 'locked' into their jobs because preexisting conditions exclusions make it expensive for individuals with medical problems to relinquish their current health insurance. I estimate the degree of job-lock by comparing the difference in the turnover rates of those with high and low medical expenses for those with and without employer-provided health insurance. Using data from the 1987 National Medical Expenditure Survey, I estimate that job-lock reduces the voluntary turnover rate of those with employer-provided health insurance by 25 percent, from 16 percent to 12 percent per year.
Navigation Conditions at Mitchell Lock and Dam, Coosa River, Alabama: Hydraulic Model Investigation
No full textSource: https://erdc-library.erdc.dren.mil/jspui/Mitchell Lock is the second navigation structure proposed for the development of navigation in the Coosa River waterway. The 84- by 600-ft lock will be located at Mitchell Dam and powerhouse about 37.3 miles upstream of the mouth of the Coosa River near Verbena, Alabama. A fixed-bed model reproducing about 4 miles of the Coosa River and adjacent overbank areas to an undistorted scale of 1:120 was used to provide some general information on navigation conditions with the proposed designs and to develop such modifications as might be required to eliminate conditions that would adversely affect navigation. Results of the investigation revealed: (A.) With medium to high flows, navigation conditions at the Highway 22 Bridge were hazardous for both upbound and downbound tows due to the high velocities and limited width provided through the navigation span with the existing piers and low superstructure. Navigation conditions were acceptable at the bridge for low flows. (B.) With the first lock alignment (Plans A and A-1), navigation conditions were acceptable with the 35,000-cfs flow only. With flows greater than 35,000 cfs, navigation conditions were hazardous in the upper pool due to the upstream guard wall perpendicularly intersecting the currents. (C.) With the second lock alignment (Plans B, B- 1, B-2, and B- 3) , navigation conditions were acceptable for the 35,000- cfs flow. With flows higher than 35,000 cfs, navigation conditions were hazardous in the lower pool due to the current alignment, high velocities, and the short maneuvering distance between the lock approach and the Highway 22 Bridge. (D.) With the third lock alignment (Plans C and C-1), navigation conditions were acceptable for all flows evenly distributed through the gated dam up to and including the 90,000-cfs flow. With the modifications in Plan C-1, the navigation conditions were improved in the lower lock approach with the low flows and the 65,000- cfs unevenly distributed flow. Navigation conditions were hazardous with flows greater than 90,000 cfs due to the current alignment, high velocities, and the limited clearance at the Highway 22 Bridge. (E.) Flows unevenly distributed through the gated dam could cause navigation problems in the lower pool. (F.) Navigation conditions would be hazardous for tows in the upper lock approach canal during lock filling. (G.) Navigation conditions would be hazardous for tows at the end of the lower guard wall when emptying the lock into the lower approach with no riverflow. The problem was eliminated by a riverflow of 35,000 cfs or by emptying the lock into the river
Lock Nut.
No full textPatent for a new and improved lock nut design, including illustrations, that efficiently and reliably "locks the nut against rotation upon the bolt" (lines 14-15)
Lock capacity and traffic resistance of locks
No full textLock capacity and traffic resistance are factors which play an important part in the assessment of future traffic through existing locks and in the determination of the number and size of new ones. In this context lock capacity means the maximum quantity of shipping which can be locked per unit of time in the prevailing conditions, if a lock is operating continuously with full chamber(s). The resistance is reflected in the time lost by shipping due to locking. The present publication deals with methods of determining lock capacity and resistance. The methods relate to eargo-carrying inland waterway vessels of the type operating on Western European waterways
Technical feasibility of the Tilting Lock: Structural and morphological analysis of the trench required for the Tilting Lock in a case study at the Haringvliet bridge
No full textThe Tilting Lock is an innovative solution for locations where road traffic crosses marine traffic overhead by a bridge. The occurrence of traffic jams at a bridge during the passage of vessels can be reduced by the construction of a Tilting Lock. By 'submerging' the vessels in the Tilting Lock underneath the bridge, the Tilting Lock increases the available air draft for vessels. Due to the Tilting Lock, vessels can pass a fixed bridge span underneath without hindrance for the road traffic on top of the bridge. The main challenge of the Tilting Lock is the large depth that is required for the implementation of the Tilting Lock. Due to the circular shape of the Tilting Lock, excavations are required up to 30 meter below the current bottom surface of the Haringvliet estuary. These large excavations will interfere with the pile foundation of the Haringvliet bridge piers. In the case study, the feasibility of the excavations that are required for the Tilting Lock was evaluated.Civil Engineering and GeosciencesHydraulic EngineeringHydraulic Structure
GPS loss of lock statistics over Brazil during the 24th solar cycle
No full textA statistical analysis of Loss of Lock (LoL) over Brazil throughout the 24th solar cycle is performed. Four geodetic GPS dual-frequency (L1, L2) receivers, deployed at different geographic latitudes ranging from about 25° to 2° South in the eastern part of the country, are used to investigate the LoL dependence on time of the day, season, solar and geomagnetic activity. The results of the analysis show that LoL is most likely in the post-sunset hours during summer and equinox, especially within the southern crest of the Equatorial Ionospheric Anomaly (EIA), in a region between about 10°S and 25°S of geographic latitude, matching the typical behaviour of scintillation over Brazil. This is confirmed by the correlation found between the relative occurrence of LoL (LoL (%)) and the Rate Of TEC Index (ROTI), used as a proxy of scintillation index and calculated for each receivers along the entire period of investigation. The LoL (%) for given solar and geomagnetic indices show some correlation with increasing the severity of the index. This correlation is strongest in the area of the southern crest of the EIA, while there is little to no apparent impact closer to the equator, depending on the index. LoL (%) increases with increasing geomagnetic disturbances, varying between ~1% and ~10% for AE ranged between 400 and 1200 nT, and exceeding 3% when Dst is around −100 nT, both related to moderate-severely disturbed conditions
Conceptual design of the Guard Lock for Strandeiland Flood Defence
No full textIn response to Amsterdam’s housing shortage, IJburg on the east side of Amsterdam, is being devel- oped. IJburg consists of six artificial islands in total on which about 20,000 homes for 50,000 residents are being built. Strandeiland (Beach island in English), located in the lake called IJmeer, is one of these artificial islands which is currently being developed to accommodate approximately 20,000 residents. This project aims to introduce approximately 8,000 homes. However, the establishment of Strandei- land presents hydraulic safety concerns, especially with the presence of extreme low water levels and fluctuations due to wind set-up and set-down.Strandeiland will feature an inland water with high recreational value for residents. This inland water will also provide access for recreational boating. Wind set-down and set-up can create extreme water level differences in this inner water. These water level differences are unfavorable and create danger to the stability of the island. These fluctuations pose a severe challenge to the stability and functionality of the island’s water infrastructure. Two primary solutions were evaluated: the adaptation of the inner quay wall or the implementation of a guard lock. Making the inner quay wall suitable for the water level differences brings several implications:• Restrictions on utilities: Because the inner quay wall would be marked as primary flood defence, no pipes and cables would be allowed inside the wall.• Design constraints: When the quay wall serves as the primary flood defence, construction on its inner slope and tree planting is prohibited. This would negatively impact the aesthetics of the waterfront and limit the housing construction space.• Increased height requirements: The inner wall has to be higher according to primary flood defence regulations, this would escalate construction costs.• Higher strength sheet piles: A higher strength of sheet piles has to be used to withstand ex- tremely low water levels which would also lead to escalating construction costs.Adapting the Inner Quay Wall, while feasible, introduces significant design and functional constraints. Because of these constraints, this option is less desirable and implementing a guard lock is the favor- able solution to solve the water level fluctuations.The guard lock as part of the primary flood defence controls extreme water level variations, ensuring Strandeiland’s water infrastructure’s integrity. The Guard Lock not only modifies the primary flood de- fence location, reducing its length considerably but also mitigates the constraints associated with an adapted inner quay wall. The water level spread is set from the program of requirements at NAP -0.6 meters and NAP +0.1. The current estimate is that this will require the lock to close 10 times a year, which is considered acceptable. A movable bridge is integrated which functions both as a neighbor- hood connector and a part of the beachside boulevard.The main objective during the design phase is to develop a Guard Lock concept for Strandeiland that facilitates the management of water level fluctuations while accounting for potential failure mechanisms. Dimensions for the Guard Lock were determined based on the standard vessel, leading to lock cham- bers measuring 22 meters in length and 7.6 meters in width. Anticipating approximately ten annual guard lock closures in extreme scenarios, the F/E system is not included initially. To facilitate a possi- ble future inclusion of a F/E system, the core dimensions are based on two lock chambers resulting in an overall structural length of 36.46 meters.Different gate designs were evaluated for the guard lock design: Mitre Gates, Rolling/Sliding gates, Lift gate (submersible), Lift gate (upward direction), Radial gates and Single-leaf gates. The first step was to check whether the different gate types were suitable for the situation in which Strandeiland is, looking at space and and vertical clearance. The lift gate in upward direction and the rolling sliding gate were considered unsuitable for this purpose. The elevator gate limits vertical clearance and the rolling sliding gates takes to much space besides to the lock. The remaining gate types were measured in a multi-criteria analysis, which resulted in a double set of mitre gates ensuring both-way retention. Because of safety and energy efficiency, but especially because of local knowledge and possibilities for maintenance, electromechanical driving mechanisms were chosen for the gates instead of an hydraulic driving mechanism.Key design elements of the core construction of the guard lock consist of the concrete structure con- sisting of the walls and the floor slab. After performing the stability checks for the bearing capacity, overturning and piping the strength calculations are done for the floor slab and the walls of the con- crete structure. The reinforcement calculations are providing detailed reinforcements for the floor slab and walls.The pile foundation is another main component of the structure. The vertical bearing capacity check indicates that no pile foundation is needed, but because non uniform settlement is expected a pile foun- dation will be included. Three different layers were evaluated to check which one was the best fit for the guard lock of Strandeiland. As the first layer is determined to be suitable to bear the load of the structure, this layer has been used. This is the most cost effective for the pile foundation design, as there is less material needed for the pile foundation design. The calculations show that 45 piles with an diameter of 0.8 m each satisfies the need to prevent non-uniform settlements under the structure.The last component which has been determined is the gate height. The process for determining gate height utilized Reliability-Based Design (RBD) principles. Reliability-Based Design (RBD) ensures the gate height is optimal in terms of cost and safety. In this way an effective design for the gate height is obtained. A comprehensive fault tree analysis, combined with a Monte Carlo analysis, established the final gate height at 5.05 meters corresponding to NAP + 1.55 m, as shown in Figure 1.Civil Engineering | Hydraulic Engineerin
Technology transfer and sustainable development in emerging economies
No full text(WP 01/03 Clave pdf) This paper aims to show how the process of diffusion of "clean technologies" confronts a variety of forces at the macro level that create systematic, technological and institutional barriers to their adoption. There is abundant literature on the role of technology transfer in the development of emerging economies, but this perspective is clearly new. What needs to be borne in mind is the possibility that the transferred dominant technology may be subject to a techno-institutional lock-in at its source that does not allow the diffusion of environmentally superior alternative technologies.Developing economies, Sustainable development, Techno-institutional lock-in, Technology transfer
Perceived risk of lock-in in the front-end phase of major transportation projects
No full textLock-in is defined as the tendency to continue with an inefficient decision or project proposal. The front-end phase is critical to project success, yet most studies have focused on lock-in in the implementation phase. Moreover, little is known about the way in which decision-makers perceive the risk of lock-in. In this paper we identify determinants of lock-in in the front-end phase and we reveal decision-makers’ perceptions of risk of lock-in. Our findings show that risk attitudes towards lock-in vary with the level of risk aversion. However, this is not sufficiently acute to drive the level of regret needed to avoid lock-in. This implies that decision-makers do not accurately assess the risk of lock-in and as such their risk perceptions are a mediating factor in the formation of lock-in. Based on escalation of commitment, path dependency, and prospect theory, the main contribution lies in providing a more comprehensive understanding of lock-in in the front-end phase
Phase-lock interference microscopy
No full textThesis (M.S.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1977. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at [email protected]. Other contact information for the Institute is available at http://www.optics.rochester.eduThe basic interference microscope uses two beams, one of which passes through or is reflected off the specimen under investigation and the other which does not. If the two wavefronts are coherent with respect to each other, then upon being recombined they will interfere. The resulting intensity pattern yields a contour map of the object where the contours represent lines of constant optical path (i.e. equal optical phase). In conventional interference microscopy, the position of these fringes is determined by visual techniques, photography, or microdensitometry. Because of the difficulty in establishing exact maxima or minima in intensity, none of these techniques can measure fringe position to better than 1/10 of the fringe spacing.
The basic concept of phase-lock interference microscopy is the introduction of a known temporal phase modulation in one arm of the interferometer. The intensity output of a detector located in the fringe pattern is used as part of an optical feedback control which can be monitored to provide a measure of optical path difference. The spatial distribution of phase is determined by scanning the interference pattern across a stationary detector.
This thesis describes the design and operation of an incident light phase-lock interference microscope. It will be shown that the system provides state-of-art accuracy in phase measurement with the provision for
scanning rates faster than other A. C. interferometers presently in operation
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