Effects of competing environmental variables and signage on route-choices in simulated everyday and emergency wayfinding situations

This study examined the relative influence of environmental variables (corridor width and brightness) and signage (directional and exit signs), when presented in competition, on participants' route-choices in two situational variables (everyday vs. emergency), during indoor wayfinding in virtual environments. A virtual reality-based methodology was used. Thus, participants attempted to find a room (everyday situation) in a virtual hotel, followed by a fire-related emergency egress (emergency situation). Different behaviours were observed. In the everyday situation, for no-signs condition, participants choose mostly the wider and brighter corridors, suggesting a heavy reliance on the environmental affordances. Conversely, for signs condition, participants mostly complied with signage, suggesting a greater reliance on the signs rather than on the environmental cues. During emergency, without signage, reliance on environmental affordances seems to be affected by the intersection type. In the sign condition, the reliance on environmental affordances that started strong decreases along the egress route.     

Improved Prony algorithm to identify multipath components

An improved Prony algorithm, code-named SVDP (singular value decomposition Prony), is proposed for identifying discrete multipath components. The new technique has been applied to data obtained from both laboratory and field experiments. The superiority of the algorithm in determining the number of rays present, and also in resolving close rays, is demonstrated.     

Optimum utilization of the channel capacity of a satellite link inthe presence of amplitude scintillations and rain attenuation

By considering the global fading process on the link caused by rain attenuation and amplitude scintillations, particularly at K_a band, it is possible to derive a long-term statistical model of the satellite channel capacity. The four-parameter distribution, which combines amplitude scintillations and rain fade within an up/down link system, is presented. Also presented are the degradation (and improvement) of bit error rate (BER) in the presence of amplitude scintillations, thus complementing the flat fade effect due to rain only. By implementation of adaptive communication systems, a more efficient channel capacity utilization is possible. The concepts and the use of novel analytical expressions combining a log-normal model of rain fade with a Moulsley-Vilar distribution for scintillations are illustrated. These are then applied to a very-small-aperture terminal (VSAT) example of a 29/19-GHz digital communications link through the Olympus satellite using M-ary phase shift keying (PSK) modulation schemes     

Analysis of Moderate and Intense Rainfall Rates Continuously Recorded Over Half a Century and Influence on Microwave Communications Planning and Rain-Rate Data Acquisition

This paper is concerned with the statistical investigation of a massive data bank of 49 years of rainfall rateRcontinuously recorded in Barcelona using a rain-rate gauge with ten seconds response time. With radio communications in mind, the paper addresses and reviews in detail: 1) reliable statistical model forR, 2) number of years required to obtain a database from which to derive a reliableR-distribution, and 3) the CCIR worst-month concept. The research has shown that the generalized Paretoaexp(-muR)/R^{b}gives nearly perfect fit for all ranges ofRfollowed closely by the gamma distribution, and the simpler square root (R^{1/2}) normal distribution gives excellent fit too. The log-normal distribution was unsatisfactory forR geq 60mm/h. The spread of the yearly distribution ofP(R)is cube root normally distributed([P(R)]^{1/3})and between 7 and 10 years are required before a reliable average distributionP(R)can be obtained. The study of theP(R)return time in years is also presented. High resolution ofP(R)is presented looking at the evolution of the annualP(R)in terms of the hourly and monthly contributing parts revealing statistical features such as the location in time of rain rates above 50 mm/h. Finally, the study shows that the calendar month contribution toP(R)remains at all times well below the synthetic CCIR worst month and recommendations are then given about its use.     

Determination of cyclodextrin inclusion constant for aromatic carbonyl compounds through spectrophotometric and electrochemical methods

α- and β-Cyclodextrins cavity inclusion constants (K_i) were determined for a series of benzaldehydes and acetophenones by using two different methods: Benesi-Hildebrand (BH) UV/vis spectroscopic method and electrochemical current (EC) method, determined by cyclic voltammetry. The values determined in the group of benzaldehydes varied from 322 ± 27 to 5688 ± 317 mol⁻¹ dm³ for UV/vis method, and 342 ± 19 to 7386 ± 142 mol⁻¹ dm³ for EC method. The values determined in the group of acetophenones varied from 2201 ± 88 to 9125 ± 251 mol⁻¹ dm³ for UV/vis method, and 1473 ± 33 to 7555 ± 187 mol⁻¹ dm³ for EC method. The equilibrium time estimated for UV/vis spectroscopic (BH) method was 240 min and for the cyclic voltammetry (EC) method was 310 min. Notably, despite their limitations, both methods were suitable and reliable for inclusion constant measurement, if the equilibrium time of the system is well established.     

Characterization of hydroxyl-terminated polybutadiene

¹H and ¹³C NMR spectra were used to study the structure of hydroxyl-terminated polybutadiene (HTPB) obtained by using hydrogen peroxide as initiator and an alcohol as solvent. This alcohol was introduced into the polymer chain, forming a hydroxylated end group. The subject has aroused some argument in the literature and is considered further in our discussion of reaction mechanisms. Received: 29 November 1996/Revised: 4 December 1996/Accepted: 9 December 1996     

Comparison of endoscopy, radiology and scintigraphy with Tc-99m-exametazine labeled leukocytes and In-111 labeled human polyclonal immunoglobulin G in the diagnosis of inflammatory bowel disease

BACKGROUND: To assess the prognostic value of dipyridamole stress echocardiography in survivors of a first uncomplicated acute myocardial infarction. PATIENTS AND METHODS: A total of 75 patients (68 men, 7 women) aged 58 years (range, 37-77) were studied 3-5 days after a first acute myocardial infarction and followed up for a mean of 10 months. Dipyridamole infusion was administered at high doses: 0.56 mg/kg, adding 0.28 mg/kg if the test was still negative. Two-dimensional echocardiography was continuously recorded during infusion and the test was considered positive if a decrease in regional contractile function appeared and negative if no assynergy was observed up to 15 min after the beginning of dipyridamole administration. A wall motion score index of regional function was derived by summation of individual segment scores divided by the number of interpreted segments. This was calculated for rest and peak dipyridamole echocardiograms. Fifty of 75 patients underwent coronary angiography based on clinical criteria. RESULTS: There were 31 coronary events: 4 deaths, one reinfarction, 13 angina. Thirteen patients underwent coronary revascularization (9 bypass and 4 angioplasty). Dipyridamole echocardiography was positive in 29 patients (39%) and negative in 46 patients (61%). Twenty patients (69%) presented coronary events in the group of positive test versus only 11 (24%) of negatives (p = 0.0001). Four patients died in the positive group while none in the negative group. Sensitivity, specificity and accuracy for all cardiac events were 65, 80 and 73%, respectively. Significant variables from univariate analysis were dipyridamole stress echocardiography response, wall motion score index at peak dipyridamole, ischemic changes in ECG and treatment with two or more antianginal drugs. Multivariate analysis showed positive dipyridamole echocardiography as the only independent prognostic factor to predict cardiac events in postmyocardial infarction patients (RR = 2.56; 95% CI = 1.12-5.84). Four of 19 patients with one vessel disease and 17 of 22 patients with 2-3 vessel disease presented a positive dipyridamole test; whereas the test was negative in the remaining nine patients with normal coronary angiography. CONCLUSION: Dipyridamole stress echocardiography is a safe and feasible pharmacologic stress imaging method to stratify postmyocardial infarction patients at risk of cardiovascular events.     

A new analytical–experimental method for the identification of stability lobes in high-speed milling

Increased working speeds and accelerations of high-speed machining produce excitation of oscillations and cause dynamic problems. These problems affect the tool life (tool wear and tool failure), produce shoddy end surface, reduce productivity, produces scrap parts and affect the environment. A chatter’s analytical prediction method was combined with experimental multidegree-of-freedom systems modal analysis to achieve the objective of generating a new method to obtain the stability lobes information. This paper describes the development of this new method which obtains the stability information for some vibration modes that can be used to graph the stability lobes for high-speed milling, and these to help in the selection of parameters for chatter free operations. Some tests were carried out to demonstrate the quality of this method and the accomplishment of the proposed goals.