Testing Procedures for Open Circuit Air Diving H ELMETS AND Semi-Closed Circuit Mixed Gas Diving Helmets

1973 ◽  
Author(s):  
S. D. Reimers
Keyword(s):  
Open Circuit ◽  
Closed Circuit ◽  
Mixed Gas ◽  
Testing Procedures

Field Comparison of Open-Circuit Scuba to Closed-Circuit Rebreathers for Deep Mixed-Gas Diving Operations

2002 ◽  
Vol 36 (2) ◽  
pp. 13-22 ◽  
Author(s):  
Frank A. Parrish ◽  
Richard L. Pyle
Keyword(s):  
Support System ◽  
Scuba Diving ◽  
Open Circuit ◽  
Closed Circuit ◽  
Mixed Gas ◽  
Black Coral ◽  
Time Requirements ◽  
Fishery Data ◽  
Dive Profile ◽  
Decompression Time

A comparison of open-circuit scuba diving to closed-circuit (“rebreather”) diving was conducted while collecting fishery data on black coral beds in Hawaii. Both methodologies used mixed gas from the same ship-based support system. The comparison was based on a series of eight dives, four open-circuit and four closed-circuit. These were used to make a direct-comparison of the gear in a square dive profile, a multilevel profile and two dives of varying profiles. Four general criteria were considered: time requirements for topside equipment preparation and maintenance, consumption of expendables, decompression efficiency, and potential dive durations and bailout capabilities for each of the two technologies. The open-circuit divers required 4 times as much topside equipment preparation as the rebreather divers, consumed 17 times as much gas, and cost 7 times more in expendables. The open-circuit divers incurred 42% more decompression time for the square profile dives and 70% more decompression time for the multilevel profile dives than the closed-circuit dive team. Most of the decompression advantage for the closed-circuit team is from the benefit of real-time decompression calculations, but some benefit comes from the breathing gas optimization inherent to rebreathers. For a given mass of equipment, the rebreathers allow for as much as 7.7 times more bottom time, or emergency bailout capability (depending on the chosen depth of the dive), compared with the open-circuit system.

Air flow quality analysis of an open-circuit boundary layer wind tunnel and comparison with a closed-circuit wind tunnel

2020 ◽  
Vol 32 (12) ◽  
pp. 125120
Author(s):  
María Jiménez-Portaz ◽  
Luca Chiapponi ◽  
María Clavero ◽  
Miguel A. Losada
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Air Flow ◽  
Open Circuit ◽  
Closed Circuit ◽  
Quality Analysis ◽  
Flow Quality

EVALUATION OF THE EFFECTIVENESS OF A CLOSED CIRCUIT IN COMPARISON WITH AN OPEN CIRCUIT OF CARDIOPULMONARY BYPASS

2021 ◽  
pp. 44-47
Author(s):  
Berik Tuishiev ◽  
Gulzhan Bayzhan ◽  
Sabina Samitova
Keyword(s):  
Cardiopulmonary Bypass ◽  
Aortic Valve ◽  
Postoperative Period ◽  
Open Circuit ◽  
Closed Circuit ◽  
Control Group ◽  
Study Group ◽  
Valve Insufficiency ◽  
Group 5 ◽  
Group 2

Objective is to evaluate the effectiveness of closed-loop surgeries with the planned duration of cardiopulmonary bypass more than 2 hours in the immediate postoperative period. Materials and methods. A study was carried out in the clinic over 10 patients (average age 47-56 years) with Diagnoses: Ascending aortic aneurysm, FC 3 aortic valve insufficiency, who underwent surgery for ascending aorta replacement, aortic valve replacement with coronary artery reimplantation. The patients were divided into 2 groups, the 1st group (5 patients) is the control group using an open cardiopulmonary bypass circuit, the 2nd group (5 patients) is the patients using a closed cardiopulmonary bypass circuit. The total time of cardiopulmonary bypass in both groups was 125-187 minutes. Results. In the 2nd study group, drainage blood loss significantly decreased, on average 60-100 ml compared to the control group, where the average drainage loss was 600-1500 ml. The need for blood transfusion was 5.1% in the 2nd group, compared with 43.4% in the control group. In the study group 2, the number of platelets in the postoperative period in patients was higher than in the control group. Conclusion. This study shows that a closed circuit, compared to an open one, allows complex heart surgeries with a planned duration of extracorporeal circulation of more than 2-3 hours.

scholarly journals Sediment Microbiota in Response to Circuitry of Sediment Microbial Fuel Cells, Revealed by 16S rRNA Gene Amplicon Sequencing

2021 ◽  
Vol 10 (46) ◽  
Author(s):  
Yasuyuki Takemura ◽  
Masataka Aoki ◽  
Thao Tran P. ◽  
Noriko Tomioka ◽  
Keiichi Kubota ◽  
...  
Keyword(s):  
Fuel Cells ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Anode Material ◽  
Microbial Fuel Cells ◽  
Amplicon Sequencing ◽  
Eutrophic Lake ◽  
Open Circuit ◽  
Closed Circuit ◽  
Rrna Gene

Information about sediment microbiota affected by sediment microbial fuel cells (SMFC) is limited. A laboratory-scale SMFC was applied to a eutrophic lake sediment under closed-circuit/open-circuit conditions. We analyzed the prokaryotes in the sediment adhering to the anode material. The archaeal family Methanoperedenceae was a predominant group under closed-circuit conditions.

scholarly journals A process mineralogy approach to study the efficiency of milling of molybdenite circuit processing

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ataallah Bahrami ◽  
Morteza Abdollahi ◽  
Mirsaleh Mirmohammadi ◽  
Fatemeh Kazemi ◽  
Abolfazl Danesh ◽  
...  
Keyword(s):  
Size Distribution ◽  
Open Circuit ◽  
Closed Circuit ◽  
Destructive Effect ◽  
Mill Product ◽  
Flotation Process ◽  
Comminution Process ◽  
Particles Size Distribution ◽  
Mineralogical Study ◽  
Mill Feed

AbstractThis study is conducted with the aim of investigating the efficiency of open and closed-circuit molybdenite ore comminution processes (primary and secondary mill, respectively), through mineralogical study of mills feed and product. For this purpose, particle size distribution, minerals distribution, degree of liberation and interlocking of minerals in mills feed and product were studied. According to the results, chalcopyrite, molybdenite, pyrite and covellite constitute the major part of the mineral composition of open-circuit mill feed. Minerals at the mill product, in the order of abundance include liberated molybdenite particles, liberated chalcopyrite and interlocked chalcopyrite with pyrite, liberated and interlocked pyrite particles, and associated silicate gangues. The d50 values of the feed and product particles of the open-circuit mill are equal to 13.80 and 13.40 microns, respectively. Degree of liberation of molybdenite for the feed and product of this mill is almost the same and is equal to 98.0%. Closed-circuit mill feed includes, in order of is abundance, liberated molybdenite particles in the form of blades and irregular polygonal shapes, liberated and interlocked chalcopyrite, and liberated and interlocked pyrite particles with gangue minerals. Molybdenite particles in the mill product are almost completely liberated, and the degree of liberation values of chalcopyrite and pyrite are 84.40% and 91.40%, respectively. According to particles size distribution of the feed (d50 equal to 25.03 microns) and the product (d50 equal to 24.24 microns) of closed-circuit mill, it can be stated that comminution is not well-operated in closed-circuit mill due to the low solid percentage of closed-circuit mill feed and the inefficiency of hydrocyclone. Examination of Mo, Cu, and Fe grade variations for 10 days in both off and on modes of mill shows that closed-circuit mill does not have an impact on comminution process. It can even be concluded that the mill has a destructive effect the flotation process by producing slimes.

Closed-Circuit Versus Open-Circuit Characterization of Hard Magnets

2019 ◽  
Vol 55 (2) ◽  
pp. 1-5 ◽  
Author(s):  
J. Fliegans ◽  
G. Delette ◽  
A. N. Dobrynin ◽  
N. M. Dempsey ◽  
D. Givord
Keyword(s):  
Open Circuit ◽  
Closed Circuit ◽  
Hard Magnets

Novel Open Circuit Displacement Control Architecture in Heavy Machinery

2014 ◽  
Author(s):  
Roman Ivantysyn ◽  
Jürgen Weber
Keyword(s):  
Large Scale ◽  
Mass Movement ◽  
Operating Cost ◽  
Open Circuit ◽  
Closed Circuit ◽  
Small Scale ◽  
Hydraulic Systems ◽  
Displacement Control ◽  
Heavy Machinery ◽  
Mobile Machinery

Motivated by the ever-stricter demands by lawmakers to lower emissions of mobile machinery and increasing fuel prices, mobile machinery has gone through a paradigm shift. Fuel efficiency has become a major selling point of machine producers. Even the heavy machinery branch, which is mainly dominated by reliability, productivity and serviceability, has started to feel this change. Hydraulic systems of large scale, as can be found in mining excavators, have typically been based on simplicity and durability. Typical architectures are open-center hydraulic systems, which were designed with robustness and productivity in mind; however they lack competiveness with other hydraulic systems in terms of energy efficiency. Displacement control has shown promising potential especially in multi-actuator machines such as excavators. The technology has so far been demonstrated in closed circuit applications on small-scale machines (below 30 t). Large scale excavators however should in general be more suitable for displacement control due to their relatively small hydraulic component cost compared to the machine and operating cost, larger energy recovery potential due to larger mass movement, more flexibility in space management and greater hydraulic power installed. Large machines feature already several smaller pumps instead of a single large pump, which is important with respect to the fact that displacement control is based on one pump per actuator. A challenge for displacement control on large-scale machinery is handling their high volumetric flow-demands on the system. Today many large excavators feature a float valve, which short-circuits the cylinder chambers and ensures rapid lowering of the attachment under aiding load. Float valves ensure fast cycle times and are essential for high productivity, however incorporating this feature in displacement control is a challenge, especially in closed circuit systems. Open circuit displacement control systems have greater flexibility than closed circuit solutions in working with float-valves and dealing with the high volumetric flows. Additionally the open circuit architecture is ideal for pump-flow-sharing, the strategy to connect two or more pumps with one actuator, which can be practiced when not all actuators move at the same time. This paper compares displacement control in open circuit form with valve-controlled actuation in a mining excavator and shows several fuel saving potentials. The Open Center system was simulated and results were validated with measurements. The proposed open circuit displacement control solutions are implemented virtually and replace the valve-controlled system. Components and system-architecture were carefully chosen in order to ensure reliability, minimal component changes and redundancy that compare to the robustness of today’s system.

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