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The lack of metrics to assess clamshell formation dredgeability limits the ability of engineers to predict the dredgeability of compact material and increases the risks associated with clamshell selection. Work done and motor energy are possible dredgeability metrics that can be estimated using micro–processor based machine monitoring. The objective of this work was to test the hypotheses that work done by the pistons during dredging, by a hydraulically actuated dredge, is a better predictor of clamshell dredgeability than motor energy. The research hypothesis was tested by comparing the measure of uncertainty surrounding mean estimates and the coefficient of variation. From this work, it can be concluded that work done is a better predictor of formation dredgeability than motor energy.

It is standard practice when treating the pelvic and para-aortic lymph nodes of seminoma patients, to use a method to reduce the dose to the testicles due to scattered radiation. A common method is the use of lead testicular shields (clamshells). We have developed a method of immobilizing the patient while at the same time providing a stable and reproducible position for the testicular shield.

A number of new developments in the areas of material composition, cell geometry, wall porosity, substrate contour, washcoat formulation, thermal and acoustic insulation, and clamshell and heatshield designs have occurred in recent years to meet the more demanding performance and durability requirements of automotive catalytic converters. This paper reviews the major developments in ceramic and metal substrates, stable washcoat systems, nonintumescent mounting materials, edge-shielded intumescent ceramic mats, ceramic insulation rings, dual can and dual cone packaging designs, and perforated heatshields with convection cooling. These improvements offer higher conversion efficiency, lower pressure drop and extended durability. A brief comparison of ceramic and metal substrate durability, based on laboratory tests, is also included.

Authorizing legislation for the deepening of navigation channels in Mobile Bay specifies that the new work dredged material and material from future maintenance dredging must be placed in an approved open-water disposal site in the Gulf of Mexico. Large mechanical dredges with clamshell buckets are being used for the new-work dredging. Hopper barges are loaded with the dredged material and transported by tug to the disposal site. Mechanical dredging is also the most likely technique for future maintenance. The economic loading of the hopper barges and the potential environmental impact associated with barge overflow during loading are important issues. A field study was therefore conducted to give site-specific information on the loading gains achieved by overflow and the characteristics of the overflow for conditions in Mobile Bay. Keywords: Barge scow, Clamshell, Dredged material, Dredging, Waste, Mobile Bay, Alabama, Overflow.

The hosts (I) and (II) form 1:1 complexes with alkali-metal ions (clamshell or sandwich-like structure) or with protonated aliphatic or aromatic diamines (such as 1,7-diammoniumheptane or o-phenylenediammonium dipicrate).

A study was undertaken to assess the merits of proposed design modifications to the Savannah River Site (SRS) reactors. The evaluation was based on the responses calculated by the RELAP5 systems code to double-ended guillotine break loss-of-coolant-accidents (DEGB LOCAs). The three concepts evaluated were (a) elevated plenum inlet piping with a guard vessel and clamshell enclosures, (b) closure of both rotovalves in the affected loop, and (c) closure of the pump suction valve in the affected loop. Each concept included a fast reactor shutdown (to 65% power in 100 ms) and a 2-s ac pump trip. System recovery potential was evaluated for break locations at the pump suction, the pump discharge, and the plenum inlet. The code version used was RELAP5/MOD2.5 version 3d3, a preliminary version of RELAP5/MOD3. The model was a three-dimensional representation of the K-Reactor water plenum and moderator tank. It included explicit representations of all six loops, which were based on the configuration of L-Reactor. A combination of features is recommended to ensure liquid inventory recovery for all break locations. Valve closure design performance for a break location in the short section of piping between the reactor concrete shield and the pump suction valve would benefit frommore » the clamshell enclosing that section of piping. 7 refs., 10 figs., 2 tabs.« less

The increase of cut-off walls by the single-phased diaphragm wall method was significant during the last years. There are different excavation methods for the construction of this wall type in practice: backhoe trench excavators crane with clamshell bucket attached to a kelly bar crane with rope clamshell and wall cutter like the “fraise”

Ge implanted with 1MeV Si+ at a dose of 1×1015cm−2 creates a buried amorphous layer that, upon regrowth, exhibits several forms of defects–end-of-range (EOR), regrowth-related, and clamshell defects. Unlike Si, no planar {311} defects are observed. The minimal EOR defects are small dotlike defects and are very unstable, dissolving between 450 and 550°C. This is in contrast to Si, where the EOR defects are very stable. The amorphous layer results in both regrowth-related defects and clamshell defects, which were more stable than the EOR damage.

Although most ingested foreign bodies pass through the gastrointestinal tract spontaneously, those that are sharp, pointed, or large require removal to avoid serious complications. Here we report an interesting case of a 60-year-old man who swallowed a clamshell that passed through the pylorus and was caught in the duodenum. Radiologic findings made it look like a biliary stone. Endoscopic retrieval of the clamshell with a Dormia Basket was performed safely and the patient was discharged uneventfully on the day of the procedure.

Environmental dredging creates challenges in finding areas to construct confined disposal facilities and typically results in residual contamination. In situ capping (either in place of dredging or for capping residual contaminants) can be limited by concerns regarding navigation, uniform cap placement, biointrusion and geotechnical stability. A potential solution for many in situ capping concerns is the use of a reactive material cap. A reactive material cap could greatly reduce the thickness required for the cap compared to conventional sand caps. Various reactive materials (e.g., activated carbon, apatite, organoclay, zeolite, zero-valent iron) are used for removal of organics and metals in wastewater and groundwater treatment and may be applicable to in-situ capping. There are several ways that could be used for in-situ capping with reactive materials. A layer of reactive material could be placed in bulk using a clamshell or pumped through a tremie pipe. Another option is a reactive material filled geotextile mat. A reactive material mat would have several advantages over loose placement of reactive materials, including: (1) uniform and verifiable mass per area placement of reactive or adsorptive material; (2) ability to mix reactive or adsorptive materials in defined proportions; (3) geotextiles provide separation of the reactive material from the contaminated sediment and cover material; (4) geotextiles provide a barrier to biointrusion; (5) multiaxial strength of the geotextiles provides resistance to uplift and differential settlement; and (6) geosynthetic reinforcement provides stability on sloped areas. In the United States, a carbon-based geotextile mat was constructed and successfully deployed. A barge with a crane was used to deploy the material off shore. Other deployment methods have also been used for installing geosynthetics in waterways from shoreline and would be applicable to a reactive material mat.

This splint was developed for a patient who required absolute immobilization of a distal interphalangeal joint arthrodesis when pin-track infections required premature pin removal. The splint has proven equally effective for other conditions requiring immobilization. Palmar or dorsal troughs are not effective because of discomfort, poor fixation, and distal migration. The clamshell splint is circumferential, providing the most protection from active motion. The anterior trough is lined with Otoform, which is formfitting once the impression is made around the finger. It is helpful to include the proximal interphalangeal joint in not more the 10° of flexion as an anchor to prevent distal migration and to ensure a secure fit. The following materials are required for splint fabrication: a low-temperature thermoplastic onesixteenth-inch splint material (we prefer Orfit microperforated), adhesive hook and pile fasteners, and Otoform silicone elastomere (Otoform K/C).

A clamshell incision allows simultaneous correction of aortic coarctation and intracardiac defects. This incision combines the benefits of a single incision with those of excellent exposure of the heart and the entire thoracic aorta as well as a superior cosmetic result.

Fresh-market spinach production has risen in the United States in the past few years as well as total value of the crop. Increased crop value may be attributed to more “value added” spinach products being produced and marketed. Public awareness of nutrition is rising due to more information being distributed concerning cancer prevention, antioxidants, and neutraceuticals. Spinach is high in the carotenoids beta-carotene and lutein, a known antioxidant for the prevention of age-related macular degeneration (AMD). It is also high in vitamins A, C, E, and folate, fiber, and the mineral iron. In this respect, spinach producers have an advantage over growers of salad vegetables such as lettuce. While this is an advantage, more innovative “value added” methods of marketing this product to the consumer are needed. A dark-green, semi-savoy spinach type developed at the Univ. of Arkansas was studied to determine shelf-life and storage capabilities of root cut plants in transparent clamshell containers. Plants were held at temperatures ranging from 1 to 6 °C. Leaf turgidity and visual characteristics were rated on a 1 to 5 scale. Acceptable characteristics and shelf-life of spinach stored in clamshell containers were seen up to 14 to 21 days when plants were stored at or near 1 °C. These results indicate that spinach packaged in transparent clamshell containers will maintain an acceptable shelf-life and could be beneficial to fresh market spinach producers.

Recent increases in bulk material tonnage being transported throughout the world are requiring the planning of many new ship and barge unloading installations, as well as the renovation and updating of a number of existing facilities. For many years, the clamshell unloader has been the heart of the typical unloading facility, and in spite of new unloading techniques, it will continue to play a major role in years to come. Since today’s high performance, high capacity unloader can represent an investment of several million dollars, it is important that the operation of this machine be well understood and appreciated by all those involved. The purpose of this presentation is to discuss the various types of reeving systems that are available, their major advantages and limitations, and the features that are essential to any system to insure smooth and trouble free operation.

Binuclear 'clamshell' phthalocyanines are characterised for the first time. The complexes exist in 'open' and 'closed' conformational forms. Electronic spectra and electrochemical data are reported. (Author)

The purpose of this study was to quantify the dry mass of dredged material involved in each stage of typical clamshell dredging and ocean disposal activities in order to identify and quantify “losses” of dredged material Turbidity plumes generated at dredging sites were also observed Approximately 2% of the dredged material was lost at the dredging site Of this quantity 61% was due to the dredging itself and 38% was due to intentional barge overflow Approximately 3 7% of the dredged material was lost at the Mud Dump Site during disposal Total loss of dredged material during these clamshell dredging and ocean disposal operations was calculated to be 5 6% Observations revealed that turbidity plumes were local features which traveled along the bottom for several hundred feet These plumes only persisted while dredging was occuring, and ambient conditions were established within a relatively short time after dredging ceased

A method of analyzing volatile organic sampling train (VOST) samples by megabore capillary gas chromatography/mass spectrometry has been developed to enhance compound resolution and to improve the characterization of products of incomplete combustion in stack emissions. Several analytical systems were evaluated. The combination of components which gave the best overall performance consisted of a clamshell oven used to desorb the Tenax® and/or Tenax®/charcoal VOST cartridges onto an analytical trap in a commercial purge and trap unit. The purge and trap unit thermally desorbed the contents of the analytical trap onto a megabore capillary column installed in a gas chromatograph where the VOST target compounds were characterized and quantified by a computerized mass spectrometer. All VOST target compounds showed response factors with coefficients of variation of less than 25% for triplicate analyses at four concentrations. The time of analysis using the capillary column was 30% faster than the present VOST protocol that requires packed-column gas chromatography.

The bacteriological impact of clamshell dredging Mississippi River bottom sediment (river mile 820 [about 1,320 km]) was investigated. Total coliform (TC), fecal coliform (FC), and fecal streptococcus (FS) densities were determined for dredged sediment and for water samples collected from above and below the clamshell dredge and above and below discharge of dredged material. Each sample was also examined for the presence of salmonella and shigella. Results indicated that clamshell dredging had no significant effect (at the level α = 0.05) on microbiological water quality as measured by TC, FC, FS, and FC/FS determinations. Salmonellae were detected in 7.1% of the upstream samples and in 16.7% of the downstream samples.

A classification scheme for the different forms of implant-related damage which arise upon annealing consisting of five categories is presented. Category I damage is “subthreshold” damage or that which results prior to the formation of an amorphous layer. If the dose is increased sufficiently to result in the formation of an amorphous layer then the defects which form beyond the amorphous/crystalline (a/c) interface are classified as category II (“end of range”) damage. Category III defects are associated with the solid phase epitaxial growth of the amorphous layer. The most common forms of this damage are microtwins, hairpin dislocations and segregation related defects. It is possible to produce a buried amorphous layer upon implantation, If this occurs, then the defects which form when the two a/c interfaces meet are termed category IV (“clamshell”, “zipper”) defects. Finally, category V defects arise from exceeding the solid solubility of the implanted species in the substrate at the annealing temperature. These defects are most often precipitates or dislocation loops.

Various lines of research into grab design have been tried since investigations started in 1953. It was finally decided to concentrate on the technique of using models. Laboratory apparatus was constructed consisting of one-twelfth scale clamshell and wide-span grabs which could be made to dig into suitably sized samples of iron ore, the ‘pick-up’ being measured and recorded. The main conclusions are that existing grabs are proportioned in about the best way possible, and that extra weight increases the efficiency only with very lumpy materials, where the efficiency is, in any case, low. Also, weight for weight, the wide-span grab is more efficient than the clamshell. Following analytical treatment of the grab mechanisms, results of further tests with model grabs suggest that for maximum pick-up the jaws should exert as high a torque as possible, especially towards the end of the grabbing cycle.

A static cold flow scale model test was performed in order to determine the internal performance characteristics of various STOVL exhaust systems. All of the concepts considered included a vectorable cruise nozzle and a separate vectorable vertical thrust ventral nozzle mounted on the tailpipe. The two ventral nozzle configurations tested featured vectorable constant thickness cascade vanes for area control and improved performance during transition and vertical lift flight. The best transition performance was achieved using a butterfly door type ventral nozzle and a pitch vectoring 2DCD or axisymmetric cruise nozzle. The clamshell blocker type of ventral nozzle had reduced transition performance due to the choking of the tailpipe flow upstream of the cruise nozzle.

A reclosable clamshell noise fairing system was developed and successfully flown on a Black Brant VC sounding rocket. The clamshell system involved the design of unique structural and mechanical subsystems to meet the experimenters requirements, withstand environmental conditions of sounding rocket flight and recovery, and be relatively easy to maintain with a clean interface between the experiment detectors and instrumentation section of the payload. The development of the equations of motion of the mechanism are illustrated and results of the test of the Engineering Test Model (ETM) are shown.

A thermal radiation imaging system has been developed which is capable of heating an area of 1 cm2 with up to 18 cal/cm2-sec of radiant flux with a uniformity of ±1%. The source and the optical imaging system provide a high degree of stability and reproducibility for extended periods. The radiant heat flux is achieved using a resistance-heated graphite element enclosed in an inert atmosphere. The radiant energy from the source is collected and refocused by means of a compound optical imaging system, sometimes called a “clamshell” imaging system. The high degree of flux uniformity is achieved by means of a heat flux redistributor placed at the image focus of the system.

The double clamshell arc imaging system has been successfully applied in a practical arrangement for physical property measurements. Thermal ex pansion measurements of alumina and zircon have been made to 1950 K (1670 C). An inflection in slope of the thermal expansion of zircon was observed at 1570 K indicating a possible phase transition previously unreported. Simple modifications (coating of mirrors) will provide higher temperatures (calculated at 2260 K). Electrical property measurements can be made in the fieldfree environment. (Author)