A self-heated second stage regulator for underwater divers

This article deals with the development, testing and performance evaluation of a new class of a self-heated breathing regulator for underwater divers.This class of regulators is introduced because of its capability of utilizing the energy of the compressed gas, used in supporting the lives of divers underwater, in heating the inhaled gases as well as in eliminating the problems of regulator freeze-up in cold waters.The paper presents the performance characteristics of the self-heated second stage regulators under different simulated dive temperatures, breathing frequencies and tidal volumes.Comparisons are also presented between the performance of the self-heated regulator and a conventional regulator in order to define the merits and limitations of each type under different dive conditions.The obtained results indicate that the self-heated regulator produced not only warm gases but performed successfully in zero°C waters while the conventional regulator has failed.This paper suggests the potential of the self-heated regulator as viable means for alleviating the problems of cold water diving.     

Manned Testing of the Diver Gas Recovery Installation

The Diver Gas Recovery Installation (DGRI) was evaluated at 80 msw saturation - 100 msw excursion diving on HeO2 in the Naval Medical Research Institute (NMRI) of China in April, 1995. The diving depth, lockout time, breathing gas flow rate and consumption, inspired oxygen partial pressure (PO2) and carbon dioxide partial pressure (PCO2) were monitored. The results indicated that PO2 was controlled to fluctuate from 64.3 to 84.0 kPa and PCO2 went up from 0.01 kPa up to O.I kPa during 4 hours excursion diving; recovery of breathing gas reached 95%; three divers felt well and breathed comfortably during simulating heavy work. The test showed that it met desired performance goals. The DGRI is a kind of important equipment for long duration deep dive. It enables the gases exhaled by the divers to be re-cycled, and therefore it has great social, military and economic significance for diving operation and submarine rescue.     

A self-heated first stage breathing regulator for underwater divers

This article presents a new class of first stage breathing regulators for underwater divers with built-in self-heating capabilities. In this class of regulators, the energy of the high pressure life support gas is used to heat both the inhaled gases and the regulator core in an attempt to combat problems of cold water diving.The thermal characteristics of this regulator are monitored and compared with those of a conventional regulator under different simulated dive temperatures, breathing frequencies and also under free flow conditions.The obtained results show that the self-heated first stage (SHFS) regulator delivered warm gases and performed successfully in zero°C water while the conventional regulator failed even when equipped with the environmental protection kit.This paper emphasizes the potential of the self-heated regulator as an essential part of cold water diving gear.     

Optimum design of a servo-controlled breathing regulator for underwater divers

This article deals with the analysis, synthesis and performance evaluation of the flow and dynamic characteristics of the new class of servo-controlled breathing regulators for underwater divers.Emphasis on such a class of regulators has been stimulated by their tremendous potential in extending the dive depth and duration because they reduce the diver breathing effort to a great extent. This would eliminate the unnecessary exhaustion of the diver under such extreme diving conditions and accordingly improve his work efficiency underwater.The study aims at developing rational design procedures and guides that would enable the regulator designers to select the optimal design parameters of this class of regulators. Such design guides are based on the analysis of the flow and dynamic characteristics of the servo-controlled regulator as well as the basic principle of the theory of optimum control.The study presents also experimental evaluation techniques of the dynamic characteristics of this class of regulators in order to provide common quantitative means for comparison with the conventional regulator designs.The presented results emphasize the merits and the potential of the servo-controlled regulators as essential tools of supporting the life of divers underwater.     

The effect of low level supplementary heating on diving duration

The exothermic reaction which proceeds when small sachets containing particulate mixtures of iron and magnesium are flooded with sea water, has been used for thermal support of free divers. Initial application of such generators to heating of the hands (Burton and Chan, 1981), and later extension to heating of the torso, have been described previously (Chan and Burton, 1981, 1982). Of considerable interest during field trials of the torso heating system was a strong subjective impression among those taking part, that significant increases of dive duration and decreases of perceived discomfort could be obtained with relatively low levels of power generation, for example less than 50% of that required for thermal balance. In this paper, a simple mathematical model of human stored heat loss is used to rationalize this observation. Also it successfully predicts voluntary exposure times of unheated divers who become cold. When used to estimate body heat debt, the model enables documented dives by this laboratory and by others, including recent exposures in Antarctica using low level supplementary heating, to be analysed.     

A low level supplementary heating system for free divers

A simple and effective method of heating divers in extreme cold water has been developed. The local heating concept utilizes a uniformly distributed granular mixture of magnesium and iron particles packed in small sachets. Upon activation by sea water, the two metal mixture behaves as a multitude of short-circuited electrolytic cells, producing thermal energy rather than electrical energy. The 45 mm-square sachets may be placed where heating is required on the diver's body, thus giving rise to the term “local heating”, obviously, the heating system requires no pumping device, or distribution network. Heating rate and duration of output of the sachets are controlled by particle size, and mixture ratio of the constituent Mg and Fe particles.This paper described the development, testing and performance of the heating sachets. Results of live tests in different dive situations are also presented and discussed.     

Experimental study on the 350 msw simulated heliox saturation-370 msw excursion diving

-The chief purpose of the research was to understand the physiological function change regularity, performance and adaptability of the human body living and working under high pressure for prolonged time.In January 1989, 4 naval divers entered the habital of NMRI's 500 msw saturation diving system after a series of adaptive diving training. The breathing mixture was helium-oxygen. After 55 h compression (including intermediate stages) the 350 msw depth was reached, where the divers lived and worked for 72 h 10 min. No sign of discomfort or significant HPNS was found in the 4 divers.The second and third day of the saturation exposure, the divers carried out 370 msw dry and wet chamber excursion diving 2 man-time each, the divers effectively carried out operational work under water, the total excursion time was 1 h each excursion dive.Saturation decompression started after 3-day storage exposure, the divers were gradually brought toward the surface 25 msw a day on the average by employing the linear stead     

The potential for dive tourism led entrepreneurial marine protected areas in Curacao

Despite the successful establishment of marine protected areas in the Netherlands Antilles, such as Saba and Bonaire, government-led protection of the reefs surrounding Curacao has repeatedly failed. In the absence of effective state regulation, dive operations have taken de facto control over dive sites, establishing conservation through a range of private initiatives akin to what have been referred to as entrepreneurial marine protected areas (EMPAs). The paper analyses the potential of these EMPAs to regulate access and control to dive sites and good diver practices. Using data from interviews with key actors in the dive industry and a survey of tourist divers the paper shows that achieving an island wide system of EMPAs is dependent on issues related to ownership over the reef, geographical location, and market competition. The paper concludes that the viability of such a system is not only dependent on the dynamics of the local and international dive market, in which all actors pursue their own interests, but also on the establishment of meta-governance arrangements that can provide incentive-based oversight to the entrepreneurial conservation practices of dive operations.     

潜水监控系统的应用研究

通过研究和分析潜水过程中出现的问题,设计了一套针对空气潜水的监控系统.系统利用计算机、视频监控、传感器技术,对潜水员的气源压力、供气压力、潜水深度、潜水时间及潜水过程中拍摄图像声音进行采集和记录.整个系统分为气源压力监测、潜水员深度监测和水下图像声音采集3个模块,可同时对4名潜水员进行实时监控,使水面人员可以准确地掌握...     

Heated diver decompression shelter: The “womb concept”

A hybrid thermal protection method using waste heat from a surface-mounted outboard motor is shown to create a warm “micro-climate” environment for divers. The effects of surface heater capacities, water flow rates, shelter volume and shelter insulation on micro-climate temperatures are characterized. During long, cold-water decompression stops this method offers a reliable, low-cost alternative to surface-supplied hot water suits or diver-carried heating systems. An added bonus for divers using closed-circuit breathing apparatus is prolonged durations of their carbon dioxide scrubbers when surrounded by the warm water “micro-climate”. Closed-circuit and open-circuit options of this diver decompression shelter concept are evaluated.     

Analysis of Dynamic ECG in the 80 Meters Saturation -100 Meters Excursion Heliox Dive

The study deals with the observation of the changes in the electrical activities of 8 healthy divers in the 80 msw saturation-100 msw excursion heliox dive by DCG. Results showed significant changes in the 24 h of average heart rate, the decrease of heart rate at saturation storage depth and decompression periods being 15.5% and 19.7% respectively. Fortuitous supraventricular premature beats appeared in 8 divers and ventricular premature beats in 5 divers during exposure. Transient ischemic ST-T changes in 6 divers occurred repeatedly during diving operations. The discussion puts up the view that the ST-T changes were due to the stress reaction of the body induced by the combined effect of such stress factors as hyperbaric pressure per se, high partial pressure of oxgen, noise and the closed restricted chamber environment.     

A conceptual process-based reference model for collaboratively managing recreational scuba diving in Kenting National Park

The purpose of this paper is to describe a management process to better control scuba diving on coral reefs. While the dive industry permits growth in local tourism revenues it can also create a degradation of the coral reefs if there are too many divers. Consequently appropriate management is essential. In this study, a case analysis of Kenting National Park was undertaken. The authors describe a process-based reference model and information system to better manage diving through collaboration by the different units, namely the divers, dive centers, the park office, the nuclear power plant bodies, the park police and the coastal guards. The management tool set of IDEF0 (Integration Definition for Function Modeling 0) was applied to describe the overall diving service workflow. An object-oriented analysis approach was then applied to represent the design of the collaborative model. A prototype web-based platform was constructed to demonstrate the model for in situ information that potentially could monitor diving and improve communication channels between the actors.     

Estimating the potential impact of entry fees for marine parks on dive tourism in South East Asia

Marine reserves are increasingly being established as a mechanism to protect marine biodiversity and sensitive habitats. As well as providing conservation benefits, marine reserves provide benefits to recreational scuba divers who dive within the reserve, as well as to recreational and commercial fishers outside the reserve through spill-over effects. To ensure benefits are being realised, management of marine reserves requires ongoing monitoring and surveillance. These are not costless, and many marine reserve managers impose an entry fee. In some countries, dive tourism is major income source to coastal industries, and a concern is that high entry fees may dissuade divers. In this paper, the price elasticity of demand for dive tourism in three countries in South East Asia – Indonesia, Thailand and Malaysia – is estimated using a travel-cost model. From the model, the total non-market use value associated with diving in the area is estimated to be in the order of US$4.5 billion a year. The price elasticity of demand in the region is highly inelastic, such that increasing the cost of diving through a management levy would have little impact on total diver numbers.     

Socio-economic aspects of the tiger shark diving industry within the Aliwal Shoal Marine Protected Area,South Africa

Understanding socio-economic aspects of the tiger shark Galeocerdo cuvier diving industry, including information on participant expectations, experiences and expenditure, is necessary for the effective management of the Aliwal Shoal Marine Protected Area on the east coast of South Africa. Between January and December 2007, a total of 2 133 tiger shark dives was conducted by 1 065 divers (95% CI = 946-1 198). Data were collected by means of the administration of a semi-structured survey questionnaire to 197 (18.6%) dive participants. Respondents indicated that the direct value of tiger shark diving to the Aliwal Shoal region was R12 405 274 (95% CI = R10 777 324-14 228 541). A total of 1 000 Monte Carlo simulations was used to estimate confidence intervals. On a ranking from one (poor) to five (excellent), the average participant response to overall quality of dive and standard of dive operator was 4.6 and 4.7 respectively. The majority of divers (98.0%) observed a tiger shark, at an average of four per dive. Although tiger sharks approached to an average distance of 1.6 m from divers, the majority (95.9%) felt safe and enjoyed the experience. The majority of interviewees (88.5%) supported the use of chumming for a closer ‘tiger shark experience’.     

The economic contribution of the muck dive industry to tourism in Southeast Asia

Scuba diving tourism has the potential to be a sustainable source of income for developing countries. Around the world, tourists pay significant amounts of money to see coral reefs or iconic, large animals such as sharks and manta rays. Scuba diving tourism is broadening and becoming increasingly popular, a novel type of scuba diving which little is known about, is muck diving. Muck diving focuses on finding rare, cryptic species that are seldom seen on coral reefs. This study investigates the value of muck diving, its participant and employee demographics and potential threats to the industry. Results indicate that muck dive tourism is worth more than USD$ 150 million annually in Indonesia and the Philippines combined. It employs over 2200 people and attracts more than 100,000 divers per year. Divers participating in muck dive tourism are experienced, well-educated, have high incomes, and are willing to pay for the protection of species crucial to the industry. Overcrowding of dive sites, pollution and conflicts with fishermen are reported as potential threats to the industry, but limited knowledge on these impacts warrants further research. This study shows that muck dive tourism is a sustainable form of nature based tourism in developing countries, particularly in areas where little or no potential for traditional coral reef scuba diving exists.     

Qualification Test for the Reliability of Diver Gas Recovery System

A qualification test for the reliability of a newly-developed Diver Gas Recovery System(DGRS)was carried out in the Naval Medical Research Institute of the People's Liberation Army,Chinafrom March 29 to April 2,1995.A sequential test plan of high discrimination ratio for the mean time be-tween failures(MTBF)was adopted.The test procedures simulated those of a 300 msw dive.A hyperbaricbreathing machine was used for the simulation of diver's respiratory functions.Parameters,such as divingdepth,respiratory minute volume(RMV),CO_2 production,gas flow rate,partial pressure of carbondioxide,and ambient temperature and himidity were all displayed and recorded with a microcomputer sys-tem.The results indicated that no failure occurred during the 91.5 h operation.According to the accept-ance and rejection criteria specified in the statistical test plan,a no-failure score in the 88 h operation is ac-ceptable.Therefore,the DGRS has been demonstrated to meet the requirements of MTBF specified in thecontract.     

Diet of red-throated divers Gavia stellata reflects the seasonal availability of Atlantic herring Clupea harengus in the southwestern Baltic Sea

Red-throated divers are piscivorous seabirds considered to be opportunistic feeders. The overall knowledge about their diet at sea is scarce. A large sample size of 82 by-caught red-throated divers from two winter (2001–02 and 2002–03) and three spring periods (2003, 2004 and 2005) offered the unique opportunity to analyse their dietary composition in the Pomeranian Bight. This area represents a hot spot in their winter distribution in the southwestern Baltic Sea and a marine protected area has been established due to its importance for the divers and other seabird species. Diet composition was analysed based on stomach and gut contents. The comparison of the different prey species was mainly based on reconstructed biomass using regressions between skeletal hard parts such as otoliths and original fish length and weight. The diet of the divers comprised eleven different fish species and nine different families. No interannual differences in the consumption of the nine most important prey species could be observed. However, in contrast to the other fish species the consumption of Atlantic herring and zander differed significantly between seasons. Herring supplied the majority of prey biomass in all three spring periods and zander in both winter periods. Moreover, the average length of herring consumed differed significantly between seasons. In winter, smaller herring was consumed compared to spring. The distinct seasonal changes in the diet composition were paralleled and most probably evoked by the migration pattern of the Western Baltic spring spawning herring which has its main spawning grounds adjacent to the study area. Based on the habitat requirements of the different prey species it could be inferred that mostly the coastal waters of the bight were used for foraging. Its function as spawning, nursery area and feeding ground with numerous resident and migrating fish species available might explain the important role of the Pomeranian Bight as wintering and staging area for red-throated divers in the southwestern Baltic Sea.     

A comparative study of the breathing and clearing characteristics of different types of snorkels

This article presents a comparative study of the breathing resistance and clearing characteristics of several types of commercially available snorkels in an attempt to device quantitative means that enable the divers to select the best snorkel and the designers to see the possible directions and modifications necessary for improving the performance of such important life support devices.Two test stands have therefore been built, the first to measure the breathing resistance and the second to monitor the clearing efficiency and speed of some of the commonly used snorkels.The tested snorkels varied from the simple J-type to the sophisticated wrap-around snorkels with convoluted flexible hoses and flared ends.The results obtained show that large diameter snorkels of the wrap-around design with sweeping barrels and flared ends (as the AMF Swimmaster snorkel number 2S55) offer the least breathing resistance. As for the clearing characteristics snorkels with small diameters and of the simple J-type (as the Spanish Aquasub snorkel: The Canarias) or with large diameters and sweeping barrels (as the Power Tuned snorkel of U.S. divers) possess the best clearing figure of merit.     

Diving behaviour of African penguins: do they differ from other Spheniscus penguins?

African penguins Spheniscus demersus closely resemble Magellanic S. magellanicus and Humboldt S. humboldti penguins and have similar breeding and feeding ecologies. Adults feed on pelagic schooling fish in continental shelf waters, but African penguins have been reported to have shallower dive angles and remain submerged longer for dives to a given depth than their congeners. The few data for African penguins were gathered using relatively large time-depth recorders. We measured diving behaviour of 36 African penguins provisioning small chicks at three colonies near Cape Town, South Africa. Maximum and mean dive depths were 69m and 14m respectively. Diving took place mainly during the day. Although dive depths differed between colonies, there were no significant differences in dive duration or maximum, median or mean depth. Total dive duration, descent time, bottom time, ascent time and dive angle all were strongly correlated with the maximum depth attained. The diving behaviour of African penguins is similar to that of its congeners. Diving performance probably was compromised by the data-logger used in the previous study. Comparative data from Humboldt penguins also indicate potential biases in an earlier study of this species. Care is needed when comparing the diving performance of penguins measured using different loggers.     

Biorobotic AUV maneuvering by pectoral fins: inverse control design based on CFD parameterization

Biologically inspired maneuvering of autonomous undersea vehicles (AUVs) in the dive plane using pectoral-like oscillating fins is considered. Computational fluid dynamics are used to parameterize the forces generated by a mechanical flapping foil, which attempts to mimic the pectoral fin of a fish. Since the oscillating fins produce periodic force and moment of a variety of wave shapes, the essential characteristics of these signals are captured in their Fourier expansions. Maneuvering of the biorobotic AUV in the dive plane is accomplished by periodically altering the bias angle of the oscillating fin. Based on a discrete-time AUV model, an inverse control system for the dive-plane control is derived. It is shown that, in the closed-loop system, the inverse control system accomplishes accurate tracking of the prescribed time-varying depth trajectories and the segments of the intersample depth trajectory remain close to the discrete-time reference trajectory. The results show that the fins located away from the center of mass toward the nose of the vehicle provide better maneuverability.