Low Draft Research Articles

Tailoring Conservation Agriculture to the Needs of Small Farmers in Developing Countries

Conservation agriculture (CA) is characterized by surface crop residue retention and minimal soil movement. It is a complex technology that involves not only a change in many of the farmer's cultural practices, but also a change in mind-set to overcome the use of the plow. CA is knowledge-intensive, and success with the system may depend more on what the farmer does than the level of inputs applied. However, smallholder farmers are generally characterized by weak links to information systems outside those of the community, while close community linkages tend to reinforce traditional activities. They commonly manage complex crop-livestock systems, where crop residues play an important role in animal nutrition. This, coupled with communal grazing rights, makes the retention of sufficient surface residues a difficult practice for small farmers, especially in rain-fed systems where residue production levels are low. Smallholders often have weak links to input and output markets, as well as limited access to capital and credit. These factors complicate access to non-traditional inputs, and to crop diversification and the establishment of crop rotations: an important practice to overcome pest and disease carryover in CA. Adequate equipment for direct seeding is a prerequisite for successful CA, but comparatively few resources have been dedicated to the development of direct-seeding equipment for low draught power conditions, given the relatively small profit margins associated with small equipment. All of these factors stress the need for the catalysis and development of innovation systems focusing on the development of CA in smallholder farming communities, and supporting the efforts of innovative farmers within these. Strategies for the successful adoption and management of CA practices need to address the issue of an enhanced knowledge base of individual farmers and the community.

조선시대 해선과 강선의 선형특성

A name of `Sea Ship` and `River Ship` had been used based on the comprehension for the difference of ship`s hull form in Chosun period. We can find a number of literature describing the situation which transferred the cargo from Sea Ship to River Ship because Sea Ship could not go upstream in the river of which the current is fast and the water depth is low. The reason why Sea Ship could not go upstream was that the bottom of Sea Ship was narrow, it means the non-flat bottom. Generally Sea Ship had short length, wide breadth, so L/B of 2.2∼3.0, and high draft and depth. River Ship has long length, narrow breadth, so L/B of 5.0∼6.3, and low draft and the flat bottom in order to adapt to the low water depth of the river.

초기설계 단계에서의 스트럿 설계 고찰

For passenger vessels, twin shaft types in propulsion system is generally adopted to provide a high-speed performance in low draught due to restricted operating condition in harbors or water channels. Struts of twin open shaft type support the shafts, bearings, and propellers. Therefore, strut design is needed to consider not only hydrodynamic performance but also structural and noise/vibration performance, In this paper, considerations in strut design at the initial design stage have been discussed based on existing references, numerical calculations, and their comparisons. Also, the strut design of a RoPax ferry has been carried out at the initial design stage, for an example.

The Influence of Shallow Injector Design on Ammonia Emissions and Draught Requirement under Different Soil Conditions

Incorporation of manure into soil can effectively reduce ammonia emissions after spreading. This study was aimed at finding an appropriate tine design, which shallowly injects slurry in closed slots on grassland, with relatively low draught forces and minimal emissions of ammonia. Hollow ‘tubulator’ tines were developed in six different designs and compared with a double disc tine. Horizontal and vertical forces were measured in an indoor sand bin and in field experiments. In some field tests slurry placement and ammonia emissions were also measured. With the sharp tip of the smallest tubulator (application rate of 25 t ha–1; depth of 5 cm) the draught forces in the field were from 520 to 1080 N, depending on soil. Draught forces for the double disc tine were similar or slightly lower. However, under all soil conditions, the tubulator required significantly lower vertical forces to penetrate the soil than the double disc tine. For an application rate of 35 t ha–1, draught and vertical forces for the medium-sized tubulators were about half those for the double disc tine at 8 cm depth. Ammonia losses after injection with the tubulator were 1·6% and for the double disc tine 27% of applied ammonia nitrogen. Thus, appropriate tine design can minimise ammonia losses while maintaining similar energy requirements to a conventional injector.

Effect of red clover ( Trifolium pratense L.) kill with glyphosate on tillage implement draft

Forages are often used in crop rotations in eastern Canada to both improve soil structure, add soil organic matter, and provide livestock feed. After the last cut of forage has been harvested in the forage year, the forage regrowth is usually killed with the non-selective herbicide glyphosate prior to fall tillage. Producers have noticed lower tractor power requirements for primary tillage for areas treated with glyphosate compared to non-treated areas. Field experiments were conducted over 2 years on a fine sandy loam soil near Charlottetown, PEI, Canada to measure the effect of red clover ( Trifolium pratense L.) kill by glyphosate on implement draft requirements in a subsequent tillage operation. Plots were established in a field of red clover, with three glyphosate treatments, early, late, and control (none). The glyphosate was applied with a field sprayer at the recommended rate of 0.9 kg a.i. ha −1. Draft measurements for a chisel plow at three nominal depths, 70, 140 and 210 mm, and for a moldboard plow at nominal 170 mm depth were made using an instrumented research tractor. In 2000, results showed a reduction in draft of 20, 25 and 18% for a chisel plow operating at 70, 140 and 210 mm nominal depths, respectively, and a 12% reduction in draft for a moldboard plow following the glyphosate treatment. In 1999, the treatment effect was not significant ( P>0.05) for the moldboard plow, and all but one chisel plow depth. However, there was a trend towards lower draft for both plows accompanying the glyphosate treatment. It is suggested that the reduction in tillage implement draft was due to breakdown of tissue structure and loss of mechanical strength of the plant roots accompanying translocation of glyhposate into the plant roots.

Injecting Bio Solids into Grass and Arable Crops, Part I: Design and Evaluation of a Shallow Injector

Shallow injection of liquid bio solids at depths of 50–70 mm into grass and arable crops offers many advantages over existing application methods. However, current shallow injection equipment only places the sludge or slurry into slots leaving it exposed with a high runoff risk. The objective of this study was to determine the benefits and limitations of injecting digested sewage sludge into land growing arable crops using shallow injection techniques. It is documented in two parts. One part describes the agronomic trials undertaken to determine the effect of application technique and timing on combinable crops. This part describes the work undertaken to understand the mechanics of shallow injection and develop an improved injector design. Here, laboratory and field studies were undertaken to compare both existing and new winged shallow injector designs. These showed that a winged injector penetrated better with an equal or lower draught than existing designs. The design also incorporated the sludge into the soil with minimal crop damage at rates of at least of 50 m 3 ha −1 when working 50 mm deep.

High performance tool for liquid manure injection

Injection has been recognised as the most effective method for land application of liquid manure, in terms of reducing nuisance odour and nutrient losses. A high performance liquid manure injection tool (prototype) was designed, based on a number of pre-set design criteria, including minimising the draft force requirement and soil surface disturbance, and maximising the manure–soil mixed zone. The range of manure application rates sought was up to 100 m 3 ha −1. The prototype featured an open sweep, leading tip, manure deflector and manure delivery tube. Tests of the prototype with different tool cutting widths (200, 300 and 400 mm) were performed at different injection depths (50, 100 and 150 mm) in both field and laboratory conditions. To reduce the draft force and soil surface disturbance, a tool cutting width of 200 or 300 mm should be used and injecting should be performed as shallow as practical. As compared with two commercial injection tools, the prototype required lower draft force, caused less soil surface disturbance and produced a larger manure–soil mixed zone.

A LIQUID MANURE INJECTION TOOL ADAPTED TO DIFFERENT SOIL CONDITIONS

Injection of liquid manure into soil can reduce nutrient loss through volatilization, reduce odor emission, reduce surface runoff pollution, and increase plant uptake of nutrients. A liquid manure injection tool was developed based on the following design criteria: easy adaptation, low draft force and surface exposure of injected manure, and suitability for different soil conditions and for variable manure application rates. The tool featured a chisel with a sweep and a shank. The first prototype was tested using swine manure in a field with clay soil and wheat stubble to examine the draft forces and the resultant manure exposure indices under different injection depths and manure application rates. Based on the field test results of the first prototype, a second prototype was designed with a narrower tool cutting width and a smaller rake angle, and was compared with the first prototype in an indoor soil bin (loamy sand soil and no residue cover). The tool geometry and features implemented in the design met the proposed design criteria. The second prototype required lower draft force and caused less soil disturbance when compared with existing injection tools reported in the literature.

COMPUTATION OF COBBLESTONE EFFECT WITH UNSTEADY VISCOUS FLOW UNDER A STERN SEAL BAG OF A SES

The concept of a surface effect ship (SES) is to lift the hull partly by the air cushion enclosed within two side hulls, a bow skirt and a stern seal. Consequently, it results in lower draft, resistance and motions than equivalent length catamarans in most sea states. In very low sea states, however, there is a significant design problem, which is high vertical accelerations, referred to as the cobblestone effect. The oscillations are based on resonance phenomena and are caused by the change of the cushion volume due to the incident waves. The resonance oscillations have an important damping mechanism which is derived from the air leakage flow under the stern seal bag of a SES. Hence, the accurate prediction of the leakage flow is required for the estimation of the cobblestone effect. In order to solve the unsteady flow field under the stern seal bag, a viscous flow code for numerically simulating two-dimensional incompressible flows has been developed. The governing equations to be solved are the time-dependent Navier–Stokes equations, using the artificial compressibility approach. The spatial discretization is based on a cell-centred finite volume formulation. The inviscid fluxes are evaluated by Roe's scheme with the third-order-accurate MUSCL approach. Time integration is conducted by the second-order accurate backward Euler formula and the linear equation system is solved by an approximate Newton relaxation scheme with the symmetric Gauss–Seidel iteration approach. For the resulting time integration to be conservative on a moving grid system, a geometric conservation law is introduced. A numerical procedure is presented and contributions of the viscous effects to the cobblestone effect problem are discussed.

Drafting Force of Fine Denier Polyester Fibers

In this paper, we use fine denier polyester fibers (0.8 denier) as the test material to measure drafting force in the break draft zone. The fundamental relationships between drafting conditions (such as drafting ratio, roller gauge, twist multiplier, and fiber mass) and drafting force follow the same trend as for cotton fibers. However, the drafting force curves reveal some differences between them. The character of the former reveals that it has a high drafting force value and a broader peak range. The force variation in the lower drafting ratio before the peak is low and steady, a very important parameter that is better correlated to the properties of spun yarn than the mean drafting force. In actual spinning, better quality yam is obtained with a suitably lower draft.

The marine digital terrain model of the Panarea caldera (Aeolian Islands, Southern Italy)

A Marine Digital Elevation Model (MDEM) of the still active volcanic area of Panarea caldera is presented in this paper. A fast and accurate survey was performed by means of the Differential Global Positioning System (DGPS) geodetic technique coupled with an echo-sounding gear and a real time navigation software. The instrumentation was installed on board of a low draught boat in order to collect data starting from the bathymeter of one meter. Planar positions and depths were obtained with average accuracies of 30 cm and 10 cm respectively providing a 3D map of the seafloor useful for geomorphological, geophysical and volcanic hazard applications.

Performance and management of draught animals in agriculture in sub-Saharan Africa: a review.

Use of animal power generally enables farmers in sub-Saharan Africa to increase agricultural production and improve the quality of life. Effective use of working animals depends on an understanding of the capabilities of the animals for work, their husbandry requirements and the factors which can influence their performance. These issues are reviewed in this paper in the context of the use of animal power in agriculture in sub-Saharan Africa. The type of animal used for work determines power available to the farmer. The performance of donkeys, horses and cattle have been compared in work tests. Equids are more suited to rapid low draught activities where their faster speed can be used to advantage. At higher draught forces, where speed is less important, the additional weight and power of cattle are an advantage. Use of heart rate recovery after work gives a reasonable indication of fatigue and fitness of equids, when test conditions are standardized. Although feed requirements for work are generally low, feed quality can be so poor that animals are unable to eat enough to meet energy needs for work, and so lose weight during the work season. However, improvements in work performance are not always seen following supplementary feeding in the dry season and the economics need to be considered in each case. Food availability, diseases and heat stress, the major constraints to performance of draught cattle and donkeys working in sub-Saharan Africa, are discussed.

Effect of design parameters of flat tillage tools on loosening of a clay soil

Very little research has been done to investigate soil loosening as a function of the geometry of the tillage tool and of the original soil properties and moisture content. A field experiment was conducted to observe the effects of the geometric parameters of flat tillage tools on their draft, cutting efficiency and loosening of a moist clay soil. The test tool variables included rake angles to the horizontal of 30, 60 and 90°, widths of 75 and 150 mm and depths of operation of 100, 150 and 200 mm. Measurements were taken of draft, disturbed soil cross sectional profiles and the initial area of soil disturbed by the tools. The resulting draft requirement increased with width, depth and rake angle of the tool. The cross sectional area of soil disturbed did not change appreciably with rake angle, but the significant increase in draft with angle resulted in markedly diminished soil cutting efficiency (area divided by draft). The degree of soil loosening was generally smaller at a rake angle of 60° than at 30 or 90°, and tended to be higher at greater depths of operation. In addition, a larger depth to width ratio generally increased the degree of loosening. Results for the soil studied indicate that the best implement design for low draft, high cutting efficiency and superior soil loosening should have a rake angle of about 30° and should be fairly narrow with a depth to width ratio of 2 or more.

Viscosity and Surface-Tension Effects on Wave Generation by a Translating Body

Various theoretical and experimental studies have been carried out to examine the generation of waves ahead of a translating body. Not all issues pertaining to this wave-motion problem are, however, fully resolved. In particular, mechanisms pertaining to generation of white-water instability and inception of vortices in the bow region are not fully understood. In this paper, the two-dimensional, unsteady, nonlinear, viscous-flow problem associated with a translating surface-piercing body is solved by means of finite-difference algorithm based on boundary-fitted coordinates. Effects of surface tension and surfactants are examined. Results of this work resolve certain classic issues pertaining to bow flows. A continuous generation of short and steepening bow waves is observed at low (draft) Froude number, a nonlinear phenomenon uncovered recently in the case of inviscid fluid also. This indicates that, steady-state nonlinear bow-flow solution may not exist, even at low speed. It is postulated that these short bow waves are responsible for the white-water instability commonly observed ahead of a full-scale ship. The amplitudes of these short bow waves are suppressed by surface tension, which is, possibly, the reason why white-water instability is not distinctly observed in laboratory-scale experiments. The presence of surfactants on the free surface is found to intensify the generation of free-surface vorticity, thus resulting in the formation of bow vortices. The accumulation of surface-active contaminants at the bow is hence responsible for the generation of bow vortices observed in laboratory experiments at low Froude number. At high Froude number, an impulsive starting motion of the body results in the generation of a jet-like splash at the bow and a gentle start an overturning bow wave, as previously observed in the case of inviscid bow flow.

Structures and Mechanical Properties of Cellulose Filament Spun from Cellulose/Aqueous NaOH Solution System

An attempt was made to disclose super-molecular structure and mechanical properties of new cellulose filament prepared from cellulose-aqueous alkali solution system. X-Ray crystallinity index χc(X) of the new cellulose filament was far higher than those of other commercial rayons, such as viscose including polynosic and cupro and was slightly lower than the organic spun rayon. The new cellulose filament showed the lowest degree of crystal orientation among these three kinds of cellulose fibers, because of its lowest draft and stretching ratio during the spinning process. In the new filament degree of the intramolecular hydrogen bondings (1−χam(C3)) estimated by 13C NMR method was highly developed. The mechanical loss tangent (tanδ) vs. temperature T curves of the new filament exhibited α relaxation (from higher temperature side; α2, αsh) attributed to micro-Brownian motion of the cellulose chains, two β (βa1, βa2), local mode of the chains, and γ, rotational mode of primary alcohol group at C6 position of pyranose rings, in the regions of T=250–100°C and −30∼−100°C, and near −100°C, respectively. Judging from the co relationships of these relaxation peak temperature Tmax to χc(X) and 1−χam(C3), we concluded that there exist two amorphous regions with well-developed intramolecular hydrogen bonds but less advanced intermolecular hydrogen bonds and vice-versa in the new filament. The results of thermally stimulated currency (TSC) measurements suggested that the hydrophobic interaction among cellulose chains is tightly formed in the region with the well-developed intramolecular hydrogen bonds. In this regard, χTSC peak named here was found to correspond to mechanical relaxation αsh. The tensile strength and elongation of the new filament were comparable to those of the regular viscose rayon. The new filament showed less swelling ratio and low fibrillation nature in water. Woven fabrics made from the filament gave some softness and high abrasion, compared with other commercial ones and were hard to wrinkle.

Andrew Jackson Higgins and the Boats that Won World War II by Jerry E. Strahan

858 Book Reviews TECHNOLOGY AND CULTURE nized, and thoroughly researched, this book should be useful to any scholar interested in the world history of medicine and disease. W. Wayne Farris Dr. Farrjs is currently professor of history at the University ofTennessee at Knox­ ville. He has written extensively on disease in premodernJapan, especially in Papula­ tion, Disease, and Land in EarlyJapan, 645-900 (Cambridge, Mass.: Harvard University Press, 1985). AndrewJackson Higgins and the Boats that Won World War II. By Jerry E. Strahan. Baton Rouge: Louisiana State University Press, 1994. Pp. xvi+382; illustrations, notes, bibliography, index. $29.95 (cloth). Historians of technology should know more, much more, about Andrewjackson Higgins (1886-1952). Higgins was probably the pre­ mier American designer and builder of small boats from the 1920s through World War II, best known for his design of shallow-draft landing craft used in large numbers by the U.S. Marine Corps and the U.S. Army in amphibious operations during World War II. Hig­ gins’s design entailed a tunnel stern and an unusual keel that pro­ vided considerable propulsion efficiency despite its extremely shal­ low draft. It was a marvel of low-tech engineering and played a central role in the Marine Corps’s doctrinal and bureaucratic strug­ gles to secure amphibious operations as its raison d’être during the 1930s. Jerry E. Strahan’s study is the first book-length biography of Hig­ gins. Through personal acquaintance with members of the Higgins family, Strahan has assembled and organized the bulk of Higgins’s personal papers and conducted an extensive set oforal histories with many of the principal players in Higgins Industries. Tojudge from Strahan’s narrative, which follows Higgins’s career from the 1930s through the Korean War, Higgins was an extremely driven and shrewd businessman who possessed a flair for promoting his products and himself. Higgins’s use of media to pitch his designs with the military, for example, was extremely sophisticated for the time. With the help of George Rappleyea (a name that historians of science will recognize as one of the masterminds behind the Scopes trial as a ploy to bring some excitement and fame to Dayton, Tennes­ see) , Higgins generated a blizzard of promotional statements, per­ formance evaluations, and promotional films that proved extremely effective, especially among Marine officers. Much of the dramatic tension in Strahan’s story stems from Hig­ gins’s absolute faith in the superiority of his designs and his abilities. A great deal of the narrative revolves around Higgins’s friction with the Navy’s Bureau ofShips, which had official responsibility for small boat design, including landing craft for the Marine Corps. Eager to TECHNOLOGY AND CULTURE Book Reviews 859 keep costs down, as well as to protect its turf, the Bureau of Ships promoted its own design and opposed the adoption of Higgins’s design as standard until forced to do so by the Truman Committee’s looming investigation. While Strahan’s account is clearly sympa­ thetic to Higgins, the portrait of him that emerges from the bureau­ cratic wrangling surrounding this competition is that of a supremely confident but volatile and even occasionally paranoid individual. Higgins appears to have been constantly apprehensive about intri­ cate schemes by the Navy and large shipbuilders to lock him out of government contracts. While these fears were not completely groundless, Higgins had many such altercations with other govern­ ment agencies and corporations over contracts to build Liberty ships, aircraft, and engines. Strahan’s account of these tensions (as well as Higgins’s disputes with labor unions and the War Production Board) will be very useful to historians ofmilitary technology, especially those with an appreci­ ation for the importance of low-tech engineering. Higgins’s boats literally changed the face of battle in World War II by making am­ phibious operations technically feasible. Historians of wartime in­ dustry will also find the book compelling. As a result of the war, Higgins’s business exploded from a small-scale, New Orleans boatworks into one of the largest facilities for the production of small craft in the nation; Strahan draws apt parallels between Higgins and Henry Kaiser. As with numerous wartime corporations, the...

Improvement of Planosol Solum: Part 3, Optimization of Design of Drop-Down Ploughs in Soil Bin Experiments

Soil bin test were conducted in Japan to optimize the shape of a drop-down plough for soil mixing of the second (Aw) and third (B) horizons to improve the planosol solum in China leaving the first (Ap) horizon undisturbed. The drop-down plough consisted of two plough bodies and had a low draught requirement and gave good soil mixing in Part 1 of this paper. The results showed that with a half-size model plough, the least draught and a maximum soil mixing rate were obtained when the plough height was 120-140 mm and the lift angle about 30 deg.

Improvement of Planosol Solum: Part 1, Experimental Equipment, Methods and Preliminary Soil Bin Experiments with Ploughs

Based on field cultivation tests by Zhao and soil investigations by Araya, a one to one mixing of the second (Aw) and third (B) horizons was conducted to improve the planosol solum in China, leaving the first (Ap) horizon undisturbed. This paper deals with basic soil bin tests of soil mixing with half size model ploughs in Japan. The results showed that stand-up and drop-down ploughs produced good soil mixing and required low draught forces. On the other hand, a fold-up plough could not mix the soil and required a high draught force because the furrow slices did not move smoothly over the plough.

Cardio-respiratory and plasma lactate responses to exercise with low draught resistances in standardbred trotters.

Five Standardbred trotters performed treadmill exercise with incrementally increasing trotting velocities for 2 min intervals in three different tests until fatigue. Each test was performed with draught loads of either 10, 20 or 30 kilopond (kp). Each trotting interval was followed by 2 min periods at a walk without draught load. Recordings were made of heart rate (HR), respiratory rate (RR), plasma lactate (PLA) and stride frequency (SF) at the end of each trotting interval. The HR increased to average values of 191 +/- 10,203 +/- 10 and 214 +/- 7 bpm and PLA increased to 3.8 +/- 0.7, 7.3 +/- 3.8 and 10.8 +/- 6.4 mmol/l at 9 m/s in the three tests, respectively. The HR response to exercise was significantly higher with increasing draught loads, and PLA was significantly higher with 30 kp compared to 10 kp draught resistance. The lowest respiratory rate was seen in the test with 30 kp loading. Peak oxygen uptake (VO2peak) was measured in a separate test on a sloped treadmill with increasing velocities without draught load and averaged 70.4 +/- 9.11/min. Muscle biopsies were taken from the gluteus muscle. Individual variations were seen in VO2peak, muscle fibre composition and HR and PLA responses to exercise. In conclusion, at a certain velocity a small increase in draught resistance from 10 to 30 kp significantly increases both the HR and PLA responses. At comparable work intensities the horses differed in circulatory and metabolic responses to exercise.

The Economics of Wet Versus Dry Cooling for Combined Cycle

The privatization of the British power generation industry has been accompanied by a major change in the technology employed in power station construction. Large coal- or oil-fired steam stations based on the Rankine cycle have been superseded for the moment by gas-fired combined cycle stations. Of equal significance has been the change from large concrete hyperbolic cooling towers to low profile mechanical draught towers, or even air-cooled condensers. This paper examines the technoeconomic factors that have led to the shift in cooling system design and assesses the factors that will dictate the direction of future cooling system designs.