Feeder Mechanism Research Articles

Categorisation of northern California rainfall for periods with and without a radar brightband using stable isotopes and a novel automated precipitation collector

During landfall of extratropical cyclones between 2005 and 2011, nearly 1400 precipitation samples were collected at intervals of 30-min time resolution with novel automated collectors at four NOAA sites in northern California [Alta (ATA), Bodega Bay (BBY), Cazadero (CZD) and Shasta Dam (STD)] during 43 events. Substantial decreases were commonly followed hours later by substantial increases in hydrogen isotopic composition (δ2HVSMOW where VSMOW is Vienna Standard Mean Ocean Water) and oxygen isotopic composition (δ18OVSMOW) of precipitation. These variations likely occur as pre-cold frontal precipitation generation transitions from marine vapour masses having low rainout to cold cloud layers having much higher rainout (with concomitant brightband signatures measured by an S-band profiling radar and lower δ2HVSMOW values of precipitation), and finally to shallower, warmer precipitating clouds having lower rainout (with non-brightband signatures and higher δ2HVSMOW values of precipitation), in accord with ‘seeder–feeder’ precipitation. Of 82 intervals identified, a remarkable 100.5 ‰ decrease in δ2HVSMOW value was observed for a 21 January 2010 event at BBY. Of the 61 intervals identified with increases in δ2HVSMOW values as precipitation transitioned to shallower, warmer clouds having substantially less rainout (the feeder part of the seeder–feeder mechanism), a remarkable increase in δ2HVSMOW value of precipitation of 82.3 ‰ was observed for a 10 February 2007 event at CZD. All CZD and ATA events having δ2HVSMOW values of precipitation below −105 ‰ were atmospheric rivers (ARs), and of the 13 events having δ2HVSMOW values of precipitation below −80 ‰, 77 % were ARs. Cloud echo-top heights (a proxy for atmospheric temperature) were available for 23 events. The mean echo-top height is greater for higher rainout periods than that for lower rainout periods in 22 of the 23 events. The lowest δ2HVSMOW of precipitation of 28 CZD events was −137.9 ‰ on 16 February 2009 during an AR with cold precipitating clouds and very high rainout with tops >6.5 km altitude. An altitude effect of −2.5 ‰ per 100 m was measured from BBY and CZD δ2HVSMOW data and of −1.8 ‰ per 100 m for CZD and ATA δ2HVSMOW data. We present a new approach to categorise rainfall intervals using δ2HVSMOW values of precipitation and rainfall rates. We term this approach the algorithmic-isotopic categorisation of rainfall, and we were able to identify higher rainout and/or lower rainout periods during all events in this study. We conclude that algorithmic-isotopic categorisation of rainfall can enable users to distinguish between tropospheric vapour masses having relatively high rainout (typically with brightband rain and that commonly are ARs) and vapour masses having lower rainout (commonly with non-brightband rain).

Force Analysis and Experimental Study of Separator Cam of Feeder

Aimed at the stability problem of feeder, we study distribution characteristics of separator shaft torque. By a kinematic and dynamics analysis of typical feeder Mechanism, we get the force of feeder camshaft and distribution characteristics of separator torque. We study the fluctuation of separator torque using the developed feeder torque test platform. The study shows that: the theoretical analysis and experimental research of separator torque distribution is basically consistent.

Quantification of the importance of wind drift to the surface distribution of orographic rain on the occasion of the extreme Cockermouth flood in Cumbria

AbstractThe 1.5 km grid length version of the Met Office Unified Model has been used to investigate a case of persistent orographic rain. The event gave up to almost 400 mm of rain locally in 48 h and led to severe flooding in the vicinity of the Cumbrian hills of northwest England in November 2009. A strong and moist low‐level jet (LLJ) was responsible for the heavy rain by the Bergeron seeder–feeder mechanism. The LLJ led to strong ascent and high liquid water content in the low‐level feeder cloud above the hills. The LLJ also caused the raindrops to drift a considerable horizontal distance as they fell through the feeder cloud. The version of the model that was used incorporates prognostic rain and it was run with and without the effect of wind drift. This showed that the area of rainfall exceeding 250 mm in 48 h was displaced some 8 km, taking it from a position largely upwind of a major watershed to a position largely downwind of it. Although there was flooding on both the windward and leeward sides of the hills, the most severe flooding occurred on the leeward side, notably in the catchments feeding the rivers through Cockermouth. The shift in the position of the maximum rainfall gave a 70% increase in the rainfall in these catchments when wind drift was included.

Mountain–valley precipitation differences in the northern Alps: an exemplary high-resolution modeling study

This paper investigates the dependence on environmental conditions of altitudinal precipitation differences in the northern Alps, based on high-resolution numerical simulations with the MM5 model for a selected region in the Bavarian Alps (Zugspitze mountain and surrounding valley stations). Three exemplary precipitation events representing climatological regimes with different orographic enhancement characteristics are selected. After validating the MM5 precipitation fields against the available surface observations, the model results are used to analyse the interactions of atmospheric dynamics and cloud microphysics with the local orography. The first two cases (19–22 March 1997, 05–09 February 1999) are characterized by a strong northwesterly or northerly flow, associated with large precipitation differences between the mountain and the surrounding valley stations. For these cases, the model results indicate a dominance of the classical seeder–feeder mechanism, with strong orographic lifting generating dense orographic clouds over each individual mountain ridge, which in turn intensify precipitation. The related surface precipitation maxima can be found near the mountain peaks or somewhat in the lee due to hydrometeor drifting. The third case (05–07 December 1992) represents conditions with relatively small (i.e. below climatological average) precipitation differences between the Zugspitze and the surrounding valley stations. For this event, the model results indicate that relatively weak ambient winds at and below Alpine crest level (700 hPa) were primarily responsible for the lack of substantial precipitation enhancement. Precipitation was nevertheless moderately intense because of strong frontal lifting at higher levels. In all three cases, the agreement between simulated and observed precipitation patterns is so high that there is good reason to expect that mountain–valley precipitation differences will be quantitatively predictable for nonconvective events once a sufficiently high model resolution is computationally affordable.

Use of high‐resolution NWP rainfall and river flow forecasts for advance warning of the Carlisle flood, north‐west England

AbstractOn the 8 January 2005 the city of Carlisle in north‐west England was severely flooded following 2 days of almost continuous rain over the nearby hills. Orographic enhancement of the rain through the seeder–feeder mechanism led to the very high rainfall totals. This paper shows the impact of running the Met Office Unified Model (UM) with a grid spacing of 4 and 1 km compared to the 12 km available at the time of the event. These forecasts, and forecasts from the Nimrod nowcasting system, were fed into the Probability Distributed Model (PDM) to predict river flow at the outlets of two catchments important for flood warning. The results show the benefit of increased resolution in the UM, the benefit of coupling the high‐resolution rainfall forecasts to the PDM and the improvement in timeliness of flood warning that might have been possible. Copyright © 2008 Royal Meteorological Society, © Crown Copyright 2008.

Small‐scale precipitation variability in the Alps: Climatology in comparison with semi‐idealized numerical simulations

AbstractThis study examines small‐scale precipitation patterns in a north‐Alpine region, and their dependence on the freezing level and on the crest‐level (700 hPa) wind direction and speed. On the one hand, measurements from a uniquely dense operational rain‐gauge network are analyzed for a period of 15 years (1991‐‐2005). Information on the ambient atmospheric fields was extracted from climate‐mode MM5 simulations driven with ECMWF (re‐analysis data. On the other hand, high‐resolution semi‐idealized MM5 simulations have been conducted, combining realistic topography with idealized atmospheric fields. The atmospheric flow parameters have been chosen to be representative of those used to classify the observational data, focusing on atmospheric conditions conducive to stratiform, orographically enhanced precipitation in the region under consideration.The results of the data analysis indicate a pronounced tendency for local precipitation maxima in the lee of individual mountain ridges, whereas the variability between stations in the centre of wider valleys and stations on the windward foot of individual ridges is comparatively small. This points towards a strong contribution of local precipitation enhancement due to the seeder‐‐feeder mechanism, combined with downstream advection of the precipitating hydrometeors by the ambient winds. The data analysis also reveals that strong winds and high temperatures tend to shift the precipitation field towards the interior of the Alps, whereas low temperatures and weak winds favour precipitation maxima near the northern edge of the Alps. The semi‐idealized simulations are consistent with these findings, but their quantitative agreement with the observed precipitation patterns depends on the ambient flow conditions. The closest agreement is found for atmospheric conditions conducive to strong orographic lifting, for which our present idealized flow fields were designed. Lower skill is obtained for conditions not dominated by orographic lifting, which implies that future work should include a generalization of the idealized flow fields. Nevertheless, precipitation patterns generated with semi‐idealized simulations seem to be very promising to support the spatial interpolation of point measurements (such as are needed for precipitation climatologies), which currently is usually based on statistical methods rather than physically motivated structures. Copyright © 2008 Royal Meteorological Society

Small‐scale variability of orographic precipitation in the Alps: Case studies and semi‐idealized numerical simulations

AbstractThis study presents high‐resolution numerical simulations in order to investigate the small‐scale precipitation variability in a north Alpine region with an extraordinarily high density of operational rain‐gauge stations. Some of the simulations have been conducted with realistic analysis data, considering two heavy‐precipitation cases that occurred in July and August 2005. Both cases were related to cyclonic northeasterly flow and exhibited a small‐scale precipitation distribution differing substantially from the climatological mean. Most notably, a station lying on the southwestern flank of a major mountain massif recorded precipitation amounts far exceeding all surrounding stations in both cases, although its precipitation climatology does not show outstanding values. Despite some quantitative differences, all real‐case simulations exhibit a precipitation pattern consistent with the observed one. They indicate that the small‐scale precipitation variability, including the unusual local maximum, was dominated by the classical seeder–feeder mechanism combined with downstream drift of the precipitation hydrometeors.In addition, a large number of semi‐idealized simulations have been performed, combining realistic topography with synthetic large‐scale flow conditions. Their main purpose is a systematic investigation of the factors controlling the structure and amplitude of the small‐scale precipitation variability. It is found that the ambient wind direction has the largest impact on the small‐scale precipitation patterns. Selecting a 700 hPa wind direction that differs by about 60° from the actual one yields a precipitation pattern that is completely uncorrelated with the observed data. The pattern correlation with the observed data is also degraded when the ambient wind speed is moved away from its real value, but the impact is not as large as for the wind direction. A less systematic impact is found for temperature, or freezing level, but the most realistic precipitation pattern is still obtained when the specified values approximately match those observed in the real cases. Interestingly, when choosing large‐scale flow conditions that approximately match the real ones, the pattern correlation with the observed rain‐gauge data becomes in both cases at least as high as for the best real‐case simulation. Copyright © 2007 Royal Meteorological Society

Modelling the operations of a component placement machine with rotational turret and stationary component magazine

Two major problems faced in the automated assembly of printed circuit boards are the determination of a component placement sequence and the internal arrangement of the component tapes in the feeder mechanism. The forms of these problems depend mainly on the physical design of the placement machine. The definition and solution of these optimization problems are attempted by many researchers and it is possible to find lots of relevant papers in the literature. However, most of these studies are concentrated on certain machine designs. In this study, the focus is on a particular machine type that has a rotational turret and a stationary component magazine. So far, this type of machine has received little attention among the researchers. The definition of the placement sequencing and feeder configuration problems are given and solution procedures are suggested. The performance of the suggested procedures are tested on real and randomly generated PCB assembly data.

Radar evidence of orographic enhancement due to the seeder feeder mechanism

AbstractThere are many cases where observed orographic enhancement has been plausibly attributed to the seeder feeder mechanism. To date, however, there have been few examples of radar data that clearly illustrate the concept of process, in the manner that the data presented here do. In this case study, vertical pointing radar data collected on the windward side of New Zealand's Southern Alps show two separated precipitating systems, with shallow rainfall enhanced by snowfall from aloft. Simple analysis of the synoptic conditions and rainfall data showed that this interaction did result in orographic enhancement. Further evidence of a seeder feeder event is given by simultaneous scanning radar data, which show a marked increase in raining area at the onset of the snowfall. Copyright © 2005 Royal Meteorological Society

The Design and Testing of a Cutter and Feeder Mechanism for the Mechanical Harvesting of Lentils

Although lentil is a valuable source of protein for humans and its straw is a highly valued animal feed, its production in West Asia and North Africa (WANA) is limited due to harvesting difficulties, including uneven ripening, lodging, growing of pods close to the ground, and shattering of seeds and leaves at maturity. Existing mechanical harvesting systems cause excessive seed (up to 55%) and leaf losses. Harvesting is therefore still commonly done by hand, but manual labour is becoming increasingly scarce and expensive. The objective of this study was to design and test a cutter/feeder mechanism for mechanical harvesting of lentils. A self-propelled experimental harvester, which cuts and collects shoots without threshing, was developed for this purpose. Its performance was compared to hand harvesting, in rolled and unrolled fields, using a split plot design. Lentils with 22% moisture (wet basis) were harvested, and then threshed using a stationary thresher. The experimental harvester was operated at 5 km h −1 and a cutting height of 59 mm above the ground. Shattering losses of seed and straw were not significantly different from that which occurred in hand harvesting ( F-statistic F<1). Residue losses were those left in the stubble, representing 2% of the seed and 20% of the straw, which can be partially recovered by grazing.

Development of a Fully Automated Circulating Letter Sorting Machine.

We have developed a machine that can sequence 2 000 letters into a specified order in 15 minutes. It singles out a letter from a stack of letters supplied into the feeder, transports it to a bar code reader that reads the address information, and stacks it in a bin according to the address. To increase the throughput, we have developed downward feeder, instead of upward feeder and switchback mechanism. As sorting algorithm, we have applied the radix sorting method, because of the higher throughput and simple arrangement. To sequence letters based on the method, it is necessary to repeat the sorting. After all letters have been stacked into bins, the letters are transferred from the bins to the feeder automatically. An interchanging bin / feeder mechanism makes circulating possible.

Spatial variations of wet deposition rates in an extended region of complex topography deduced from measurements of 210Pb soil inventories

The radionuclide 210Pb derived from gaseous 222Rn present in the atmosphere becomes attached to the same aerosols as the bulk of the main pollutants sulphur and nitrogen. When scavenged from the atmosphere by precipitation, the 210Pb is readily attached to organic matter in the surface horizons of the soil. Inventories of 210Pb in soil can thus be used to measure the spatial variations in wet (or cloud) deposition due to orography averaged over many precipitation events (half-life of 210Pb is 22·3 year). Measurements of soil 210Pb inventories were made along a transect through complex terrain in the Scottish Highlands to quantify the orographic enhancement of wet deposition near the summits of the three mountains Ben Cruachan, Beinn Dorain and Ben Lawers, which, respectively, lie at distances of approximately 30, 55 and 80 km from the coast in the direction of the prevailing wind. The inventory of 210Pb on the wind-facing slopes of Ben Cruachan shows an increase with altitude that rises faster than the precipitation rate, which is indicative of seeder-feeder scavenging of orographic cloud occurring around the summit. Results for Beinn Dorain show a smaller rise with altitude whereas those for Ben Lawers give no indication of a rise. It is concluded that the seeder–feeder mechanism in regions of complex topology decreases in effectiveness as a function of distance inland along the direction of the prevailing wind.

High resolution studies of rainfall on Norfolk Island, Part III: A model for rainfall redistribution

A dense network of high resolution rain gauges has provided data on spatial scales of about 1.5 km and time scales of 15 sec on Norfolk Island, where the topography is dominated by a 300 m hill that is found to modify the spatial distribution of rainfall depending on wind direction. A correlation method is used to track coherent storm motion so as to identify the dominant wind direction and speed. Transects are selected across the island in the wind direction and the rainfall interpolated along each transect. It is found that there is often a decrease in rainfall upwind of the hill, followed by an increase downwind of the peak. The ratio of downwind to upwind catches increases linearly with wind speed. These observations do not accord with the often accepted explanation using a seeder–feeder mechanism. A simple wind drift model is proposed, in which raindrops follow trajectories modified by the perturbed wind flow over the hill. The transects are approximated by bell-shaped hill profiles. Analytic solutions for potential flow over a cylinder are then used to find a streamline with a bell shape similar to a topography transect through the hill and aligned with the wind direction. This streamline is used as the solid surface boundary, thereby giving a direct analytic flow field for the bell-shaped hill. A streamfunction is found for drop motion, allowing rainfall variations to be predicted. A parameterisation is developed that explains the shape and magnitude of the observed rainfall variations along a transect. Agreement between the rudimentary model and observations is found possible to within a few percent. This indicates that the wind drift process is viable as the dominating mechanism for determining rainfall distribution in the presence of low hills when low level moisture is absent.

Effect of Added Processed Poultry Waste on Dairy Heifers’ Preference for Concentrates

Operant conditioning procedures were used to assess preference for a standard dairy concentrate containing either 0, 9, 23, or 34% processed poultry excreta. Eight 8-mo-old Holstein heifers were trained to operate a two-choice feeder in an operant chamber. When heifers pressed the muzzle plate that activated the feeder mechanism, they had access to one of the paired feeds for 3s every 15s on an average. Heifer responses were recorded electronically during daily 20-min sessions. All concentrates were fed in the operant chamber. Between sessions daily and on weekends and holidays heifers received alfalfa hay for ad libitum consumption. Data from the last five sessions, when response had stabilized, were analyzed. An average of 21 sessions was required to reach stability for a choice comparison test, but this was highly variable for individuals and ranged from 9 to 44 sessions. Data from each heifer were corrected for any bias for the right or left side, based on a comparison of responses with control sessions. There were no differences among heifers in the number of choices made during the five sessions or in deviations from random responses (.5). The number of responses and homogeneity of response differed among heifers. Heifers preferred concentrate containing less processed poultry waste; ranking of preference was 0>9>23>34% processed poultry excreta. Heifers usually rejected concentrate containing 34% processed poultry excreta.

On the modelling of warm orographic rain by the seeder-feeder mechanism

A two-dimensional model of the seeder–feeder mechanism for the orographic enhancement of rain is presented. It satisfactorily reproduces observed rainfall rate distributions and is helpful in studying some aspects of the physics of orographic rain. The modelling approach is based on the principle of continuity of the water substance and on the two-dimensional theory of small perturbations of airflow over topographical ridges of modest dimensions. The model is significantly different from those found in the literature and is used to clarify two major points. Firstly, it emphasizes that there is a range of hill dimensions for which the seederfeeder mechanism plays a major role. That is, the model predicts that a change of regime occurs for larger hills (half length > 20 km) where the seeder-feeder mechanism is no longer dominant because of the possibility of rain development within the feeder cloud and also because the horizontal scale of rain drift becomes small compared with that of the topography. Secondly, it is also suggested that the difference of wind curvature below and above a low-level jet may be important in determining the intensity of orographic rain. The physical process behind the latter finding is closely linked to partial reflection of upward propagating gravity waves which may lead to ‘resonance’ of the orographically induced vertical velocity.

On the modelling of warm orographic rain by the seeder‐feeder mechanism

AbstractA two‐dimensional model of the seeder–feeder mechanism for the orographic enhancement of rain is presented. It satisfactorily reproduces observed rainfall rate distributions and is helpful in studying some aspects of the physics of orographic rain. The modelling approach is based on the principle of continuity of the water substance and on the two‐dimensional theory of small perturbations of airflow over topographical ridges of modest dimensions. The model is significantly different from those found in the literature and is used to clarify two major points. Firstly, it emphasizes that there is a range of hill dimensions for which the seederfeeder mechanism plays a major role. That is, the model predicts that a change of regime occurs for larger hills (half length &gt; 20 km) where the seeder‐feeder mechanism is no longer dominant because of the possibility of rain development within the feeder cloud and also because the horizontal scale of rain drift becomes small compared with that of the topography. Secondly, it is also suggested that the difference of wind curvature below and above a low‐level jet may be important in determining the intensity of orographic rain. The physical process behind the latter finding is closely linked to partial reflection of upward propagating gravity waves which may lead to ‘resonance’ of the orographically induced vertical velocity.

Experimental Automatic Feeder for Seedling Transplanter

AUTOMATIC seedling transplanters have been under development for more than 20 years by various individuals and groups. With the exception of the Japanese rice transplanters, no particular automatic machine has been widely accepted by growers. Thus, a need still exists for a successful automatic transplanter design. Generally, automatic transplanters transfer seedlings from a source of supply to a planting mechanism via a feeder mechanism. This paper describes a laboratory bench model of a new feeder mechanism for free-cell seedlings. It transferred 90% of the seedlings at a rate of 30 to 60/min. Both the percentage successfully transfered and the rate of transfer will need to be increased for a successful field machine.

Numerical Simulation of Orographic Enhancement of Rain with a Mesoscale Model

Abstract Orographic precipitation enhancement associated with the feeder mechanism proposed by Bergeron has been simulated using a two dimensions model based upon primitive equations including detailed parameter microphysics. A case-by-case comparison is made between model results and each of 14 well-documented precipitation episodes in southern Wales. The model reproduces the observed strong dependence of the precipitation enhancement on the low-level wind speed, as well as the weak dependence on the upwind precipitation rate. Model results also demonstrate that a satisfactory treatment of orographically enhanced precipitation requires the linking of the dynamical, thermodynamical and microphysical processes.

Prototype of Apparatus for Supplying Powder in Minute Portions

In planning a feeder of fine powder it is necessary to study the characteristics of the powder to supply in order to ensure stable feeding. Especially it is the case with sticky or agglomerative powder which will often bring up feeding problems, and of which feeding in minute portions with high degree of accuracy is extremely difficult.This prototype apparatus has been developed with a view to coping with the fact that neither the conventional method of stabilizing bulk density, nor the method of packing the powder relying on gravity into feeder mechanism, is adequate by itself for processing the supply of powder in minute portions.By means of this prototype apparatus the powder is compressed into the groove on the roller by the rotating blade, and then it is scraped off by means of a scraper. This mechanism is employed to reduce or eliminate a large fluctuation of bulk density by packing the powder with constant rate of force.As a result a very fine feeding rate as low as from one tenth gram to hundreds of grams per minute with accuracy of 1-3% has been obtained. Much finer and more accurate feeding rate will be achieved with further improvement of mechanism.

Cue selection in discriminative operant conditioning

Stimulus conditions involved in a discriminative operant learning situation were manipulated to determine which cues were being responded to in order to solve the problem. In a situation where the SD and SΔ periods were of equal length and where a bar press resulted in a click of the feeder mechanism only during the SD period it was found that time interval and/or whether or not a bar press resulted in a pellet of food were utilized by S more so than the cue light or the click of the feeder mechanism.