Pooling stated and revealed preference data in the presence of RP endogeneity

Pooled discrete choice models combine revealed preference (RP) data and stated preference (SP) data to exploit advantages of each. SP data is often treated with suspicion because consumers may respond differently in a hypothetical survey context than they do in the marketplace. However, models built on RP data can suffer from endogeneity bias when attributes that drive consumer choices are unobserved by the modeler and correlated with observed variables. Using a synthetic data experiment, we test the performance of pooled RP–SP models in recovering the preference parameters that generated the market data under conditions that choice modelers are likely to face, including (1) when there is potential for endogeneity problems in the RP data, such as omitted variable bias, and (2) when consumer willingness to pay for attributes may differ from the survey context to the market context. We identify situations where pooling RP and SP data does and does not mitigate each data source’s respective weaknesses. We also show that the likelihood ratio test, which has been widely used to determine whether pooling is statistically justifiable, (1) can fail to identify the case where SP context preference differences and RP endogeneity bias shift the parameter estimates of both models in the same direction and magnitude and (2) is unreliable when the product attributes are fixed within a small number of choice sets, which is typical of automotive RP data. Our findings offer new insights into when pooling data sources may or may not be advisable for accurately estimating market preference parameters, including consideration of the conditions and context under which the data were generated as well as the relative balance of information between data sources.This work was supported in part by a grant from the Link Foundation, a grant from the National Science Foundation # 1064241 , and a grant from Ford Motor Company. The opinions expressed are those of the authors and not necessarily those of the sponsors.Accepted manuscrip

Gains, Losses, and Life Goals Identified by Caregivers of Individuals with Disabilities in the United States

It is often reported that caregivers of individuals with disabilities experience stress as they manage caregiving responsibilities while they make the effort to balance family and work. Thirty-one caregivers of individuals with an array of disabilities in the United States completed a qualitative survey in this pilot study that asked them to identify their gains and losses from providing care and to identify their life goals. The gains from caregiving were identified as enhanced empathy and compassion, and the losses as strained family relationships, and less personal time. The most commonly identified life goals were experiencing happiness and achieving financial stability. The implications of these results on professionals’ attempts to support caregivers and their families are discussed

Space Weather Application Using Projected Velocity Asymmetry of Halo CMEs

Halo coronal mass ejections (HCMEs) originating from regions close to the center of the Sun are likely to be responsible for severe geomagnetic storms. It is important to predict geo-effectiveness of HCMEs using observations when they are still near the Sun. Unfortunately, coronagraphic observations do not provide true speeds of CMEs due to the projection effects. In the present paper, we present a new technique allowing estimate the space speed and approximate source location using projected speeds measured at different position angles for a given HCME (velocity asymmetry). We apply this technique to HCMEs observed during 2001-2002 and find that the improved speeds are better correlated with the travel times of HCMEs to Earth and with the magnitudes ensuing geomagnetic storms.Comment: accepted for [publication in Solar Physic

Pročišćavanje čelika optimiranjem konfiguracije međulonca

In continuous casting process, liquid steel flows through the tundish, which is supposed to operate as a continuous refining finisher. To provide a functionality of such a device, a pack of tundish metallurgy techniques must be applied, whose efficiency is conditioned especially with optimal symmetrical and dynamical melt flow. Flow optimizing can be achieved through the shaping of inside tundish configuration, using flow control devices such as turbulence inhibitors, impact pads, baffles, weirs, dams, etc. The theme of the present paper is the precise employment of a turbulence inhibitor, commercially known as TURBOSTOPTM, together with a pair of baffles & a flat impact pad in slab custer to improve steel cleanliness and a fluid flow phenomenon in a two strands tundish.Tijekom procesa kontinuiranog lijevanja tekući čelik prolazi kroz međulonac koji funkcionira kao kontinuirani uređaj za završnu doradu rafiniranjem. Za osiguranje funkcioniranja takvog uređaja mora se primijeniti tehnika metalurgije međulonca čija učinkovitost je uvjetovana naročito optimalnim simetrijskim i dinamičkim tečenjem taline. Optimalizacija protoka se može postići oblikovanjem unutrašnje konfiguracije međulonca uporabom takvih uređaja za kontrolu protoka kao što su inhibitori turbulencije, zadebljanje za ublažavanje udaraca, pregradne ploče, brane itd. Tema ovog rada je točna primjena inhibitora turbulencije poznatog pod trgovačkim nazivom TURBOSTOPTM, zajedno s parom skretnih pregrada i ravnim zadebljanjem za ublažavanje udaraca u lijevanom slabu radi poboljšanja čistoće čelika i fenomena toka fluida u dvije žile međulonca

The Laryngeal Mask Airway (LMA) as an alternative to airway management in mentally retarded patients during dental procedures: research

Background: To evaluate the possibility of airway management using a laryngeal mask airway (LMA) during dental procedures on mentally retarded (MR) patients and patients with genetic diseases. Design: A prospective pilot study. Setting: University Hospital. Methods: A pilot study was designed to induce general anaesthesia for dental procedures in 15 mentally retarded patients, with airway management using a laryngeal mask airway (LMA). The parameters assessed during the pilot study included ease of LMA insertion and its seal, inspiratory pressures with controlled ventilation, visibility of the operating field and surgical comfort, recovery from anaesthesia, LMA tolerability and postoperative complications. Results: LMA insertion was successful in all of the patients, operating field visibility was good in most patients, as was tolerability, and awakening was uneventful. Serious postoperative complications bleeding, prolonged coughing and eating disorders were not observed. Conclusions: In this pilot study, the LMA was a suitable tool for airway management during dental procedures on the mentally retarded and on patients with genetic diseases. Keywords: Dental care, Mentally disabled persons, Genetic diseases, Laryngeal mask airway Southern African Journal of Anaesthesia & Analgesia Vol.10(4) 2004: 15-1

Automated condition monitoring of mill ball size distribution and grate open area

Grinding media in coarse grinding tumbling mills constitute the biggest consumable cost to a comminution processing plant, therefore it is critically important to minimize associated wear. Secondly, efficient grinding is dependent on tight control of the desired ball size distribution, or else optimum impact breakage cannot be assured. Despite the significance of minitoring ball size distribution for mill operation, no practically deployable systems are currently in industry use to measure it. This paper describes a new method for highly accurate, comprehensive, and rapid determination of ball size distribution.Accurate SAG and AG mill product size control is dependent on appropriate Grate Open Area dimensions. Wear of the grate hole edges or in the plate thickness results in an increase of the open area due to the tapered hole cross section, which can result in oversize product exiting the mill. Conversely, some grate castings feature peening of the edges during mill operation, thereby decreasing open area, and therefore preventing the desireed top size product from exiting the mill.SAG mill throughput requires grate holes to remain open or else throughput is restricted. Many grates in operation are pegged by grinding media to varying degrees of severity. This paper introduces a comprehensive, accurate and rapid method to measure and track the size and pegging status of each and all grate holes in situ, and therefore provides tracking information on the Open Area of a SAG mill. This enables operators to control the primary mill product size and therefore the opportunity to stabilize downstream processes

Digital Power Network Parameters Measurement

Exact measurement of the parameters of a power network is now possible by digital methods. The description of the proposed and realized instrument based on the digital sampling method is given. It can measure basic parameters of the three-phase power network such as rms values of voltages and currents, powers, energies, power factors and the network frequency. Questions concerning the accuracy of measurement, error sources, and error correction are also given. A method of calibration based on the frequency output is proposed and its calculation accuracy evaluated by MATLAB

Prediction of qualitative parameters of slab steel ingot using numerical modelling

The paper describes the verification of casting and solidification of heavy slab ingot weighing 40 t from tool steel by means of numerical modelling with use of a finite element method. The pre-processing, processing and post-processing phases of numerical modelling are outlined. Also, the problems with determination of the thermodynamic properties of materials and with determination of the heat transfer between the individual parts of the casting system are discussed. The final porosity, macrosegregation and the risk of cracks were predicted. The results allowed us to use the slab ingot instead of the conventional heavy steel ingot and to improve the ratio, the chamfer and the external shape of the wall of the new design of the slab ingot

Prediction Space Weather Using an Asymmetric Cone Model for Halo CMEs

Halo coronal mass ejections (HCMEs) are responsible of the most severe geomagnetic storms. A prediction of their geoeffectiveness and travel time to Earth's vicinity is crucial to forecast space weather. Unfortunately coronagraphic observations are subjected to projection effects and do not provide true characteristics of CMEs. Recently, Michalek (2006, {\it Solar Phys.}, {\bf237}, 101) developed an asymmetric cone model to obtain the space speed, width and source location of HCMEs. We applied this technique to obtain the parameters of all front-sided HCMEs observed by the SOHO/LASCO experiment during a period from the beginning of 2001 until the end of 2002 (solar cycle 23). These parameters were applied for the space weather forecast. Our study determined that the space speeds are strongly correlated with the travel times of HCMEs within Earth's vicinity and with the magnitudes related to geomagnetic disturbances