Simulation study of helicopter ship landing procedures incoporating measured flow data

The aim of this article is to investigate the use of inverse simulation to help identify those regions of a ship's flight deck which provide the safest locations for landing a rotorcraft in various atmospheric conditions. This requires appropriate information on the wind loading conditions around a ship deck and superstructure, and for the current work, these data were obtained from wind tunnel tests of a ship model representative of a typical helicopter carrier/assault ship. A series of wind tunnel tests were carried out on the model in the University of Glasgow's 2.65 × 2.04 m wind tunnel and three-axis measurements of wind speed were made at various locations on the ship deck. Measurements were made at four locations on the flight deck at three different heights. The choice of these locations was made on the basis of preliminary flow visualization tests which highlighted the areas where the most severe wind effects were most likely to occur. In addition, for the case where the wind was from 30 to starboard, measurements were made at three further locations to assess the extent of the wake of the superstructure. The generated wind profiles can then be imposed on the inverse simulation, allowing study of the vehicle and pilot response during a typical landing manoeuvre in these conditions. The power of the inverse simulation for this application is demonstrated by a series of simulations performed using configurational data representing two aircraft types, a Westland Lynx and a transport helicopter flying an approach and landing manoeuvre with the worst atmospheric conditions applied. It is shown from the results that attempting to land in the area aft of the superstructure in a 30° crosswind might lead to problems for the transport configuration due to upgusts in this area. Attempting to perform the landing manoeuvre in an aggressive manner is also shown to lead to diminished control margin in higher winds

Adjusting lactation milk yield of Zimbabwean Holstein dairy cows for the joint effects of age at calving and month of calving

A research paper on adjusting lactation milk yield of Zimbabwean Holstein dairy cows.Milk yield is influenced by both genetic and non-genetic factors. For accurate genetic evaluations there is need to account for these factors and quantify their effects on milk yield. The main objective of this study was to quantify the joint effects of age at calving and month of calving on lactation milk yield and to compute appropriate adjustment factors for milk yield. A total of 29 315 edited lactation records of Zimbabwean Holstein dairy cows collected from 1979 to 1994 by the Zimbabwe Dairy Herd Improvement Association (ZDHIA) were used. The data were divided into two sub-sets. The first set of 16 073 records was used to develop multiplicative age-month adjustment factors and for determination of genetic parameters. The second data set with 13 242 records was used for verification of the adjustment factors. This was done to test the effectiveness of multiplicative age-month adjustment factors which were developed in this study. An Animal Model was run in the Average Information — Restricted Maximum Likelihood (AIREML) software package. The multiplicative adjustment factors for lactation milk yield varied with age at calving and month of calving. The factors were highest in young cows (1.21), decreasing with increasing age at calving and were lowest (0.89) at mature age (72 to 84 months). After 72 to 84 months the adjustment factors started increasing. The adjustment factors were also highest (1.21) in summer (December, January and February) and lowest (0.89) in winter (May, June and July). Heritability estimates were highest for first lactation cows and were low for later lactation cows. The heritability estimates were similar for both adjusted and unadjusted records. The heritability estimates for the unadjusted records were 0.38, 0.26, 0.24 and 0.21 for first, second, second and over, and all combined lactations, respectively. The corresponding estimates for the adjusted records were 0.45, 0.25, 0.25 and 0.24. This study showed that age-month adjustments were effective. The local Holstein dairy industry is recommended to use these age-month adjustment factors developed using local data to eliminate biases in genetic evaluations. Heritabilities are high enough to practise an effective progeny test and selection scheme for milk yield

Mesiodistal crown diameters and tooth size discrepancy of permanent dentition in thalassemic patients

Objectives: To provide a description of mesiodistal crown diameters (MD) and tooth-size discrepancy (TSD) of the permanent dentition in patients with thalassemia major (TM) and to compare the results with those of unaffected control group. Study design: The sample consisted of 46 thalassemic patients, 25 males and 21 females aged 7.3 to 23.7 years (mean ± SD = 11.2 ± 3.9 years) and control group matched by age and sex. Dental casts of the participants were measured for MD, using a digital sliding caliper. Descriptive statistics were computed for each individual tooth. Student t-test was used for comparison of mean values between males and females as well as between thalassemic and control groups. The differences between sets of data were evaluated by analysis of variance (ANOVA). Results: All means for MD of thalassemic males and females were smaller than their controls, with 20 of the 24 comparisons being statistically significant (ranged from P<0.05 to P<0.001). In both thalassemic and control groups, males exhibited significantly larger MD than females in most instances. Canines displayed the most sexual dimorphic teeth in the dentition. Lateral incisors showed the greatest variability indicated by the coefficient of variation, while the first molars were the least variable teeth (7.6% vs. 5.3%). There were no statistically significant differences in the anterior and overall tooth-size discrepancy ratios between sexes or between thalassemic and control groups. The mean anterior ratio (79.5%) and overall ratio (92.4%) of the control group were significantly larger than of Bolton ratios; P<0.001 and P<0.05, respectively. Conclusions: The present study demonstrated that thalassemic males and females exhibited significantly smaller MD than the control group. The TSD ratios in both thalassemic and control groups were significantly larger than those of Bolton sample. These findings should be taken into account when planning orthodontic treatment for thalassemic patients

Comparison of a modified log-logistic distribution with established models for tree height prediction

The complexity of data structure from different forest stands across the world has necessitated the continuous introduction of new models in forestry. No single model is expected to provide accurate fit to all data sets. Therefore, in this study, the cumulative distribution function (cdf) of the Log-Logistic distribution was modified to construct a new height-diameter (h-d) model for Gmelina arborea Roxb plantation in Omo Forest Reserve, Nigeria. A total of 60 sample plots of 0.04 ha were used in this study. Tree diameters and heights measurement were taken on 1,189 trees. The new h-d model was termed M. LogL and its performance was compared with five established traditional h-d models that have been used in quantitative forestry study. These include: Logistic h-d, Chapman-Richards (C-R) h-d, Weibull h-d, Näslund h-d and Curtis h-d. Model assessment was based on adjusted R2, root mean squared error (RMSE), Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC) and Hannan-Quinn Criterion (HQC). The result showed that the performance of the new M. LogL h-d was comparable to other traditional h-d models used in forestry. The adjusted R2, RMSE, AIC, BIC and HQC were 0.629, 3.343, 2555.599, 2565.527 and 2555.480, respectively. However, the Logistic h-d model had the overall best fit to the data set. The order of ranking was: Logistic &gt; M. LogL &gt; Curtis &gt; C-R &gt; Weibull &gt; Näslund. Therefore, the M. LogL model can be used to predict tree height for the Gmelina arborea plantation.Keywords: Modified Log-Logistic, height-diameter, Gmelina arborea, Omo forest reserv

PRELIMINARY DIAGNOSES OF NEW BIRDS FROM MALAYSIA.

abstract not availabl