Gas production from marine gas hydrate reservoirs using geothermal-assisted depressurization method

Natural gas production from marine gas hydrate reservoirs has become attractive to the oil and gas industry in recent years. It is still a great challenge to recover natural gas from hydrate reservoirs efficiently mainly due to sand production and wellbore collapse problems associated with the production scheme of depressurization. The thermal recovery method has not been proven economical due to the high cost of energy consumption. This study focuses on using geothermal energy to assist the depressurization process so that well pressure drawdown can be reduced and thus sand production and wellbore collapse problems can be mitigated. The authors investigated the transfer of heat energy from a natural geothermal zone to a marine gas hydrate reservoir and its effect on gas well productivity using analytical models. The result of our investigation shows that the initial well productivity can be significantly improved using geothermal energy more than 10-fold. This work provides engineers with an analytical tool for the feasibility analysis of using geothermal energy to improve well performance in gas hydrate reservoirs.Cited as: Mahmood, M. N., Guo, B. Gas production from marine gas hydrate reservoirs using geothermal-assisted depressurization method. Advances in Geo-Energy Research, 2023, 7(2): 90-98. https://doi.org/10.46690/ager.2023.02.0

Equation of motion of an interstellar Bussard ramjet with radiation and mass losses

An interstellar Bussard ramjet is a spaceship using the protons of the interstellar medium in a fusion engine to produce thrust. In recent papers, it was shown that the relativistic equation of motion of an ideal ramjet and of a ramjet with radiation loss are analytical. When a mass loss appears, the limit speed of the ramjet is more strongly reduced. But, the parametric equations, in terms of the ramjet's speed, for the position of the ramjet in the inertial frame of the interstellar medium, the time in this frame, and the proper time indicated by the clocks on board the spaceship, can still be obtained in an analytical form. The non-relativistic motion and the motion near the limit speed are studied.Comment: 4 figure

An Unusual Case of Gallbladder Carcinoma with Pseudopancreatic Cyst

Generally, carcinoma of the gallbladder is an extremely unusual neoplasm, however, high incidence rates have been reported in certain parts of the world. The role of certain factors such as genetic susceptibility, lifestyle and infections of gallbladder in causing carcinogenesis is still not clearly understood. Due to its early vague symptoms and lack of serosa in the gallbladder to slow its spread, gallbladder carcinoma typically presents at an advanced stage with a five-year survival rate of less than 5%. Pseudopancreatic cyst is an uncommon but not a rare complication of acute pancreatitis and injury to the pancreas. However, it rarely presents with carcinoma of gallbladder. We present here an unusual case of gallbladder carcinoma with pseudopancreatic cyst in a 58-year old male

Job Satisfaction of Private University Teachers in Bangladesh

Job satisfaction is considered as a vital determinant of job behavior. By considering the significance of job satisfaction and the important roles of teachers of private universities in the development of education sector and knowledge employees, the aim of this study is to inspect the level of job satisfaction of teachers of private universities and also to investigate whether job satisfaction differed according to age, gender, education, level of skills, types and duration of their employment. The sample of the study comprised 233 teachers from 32 universities. Brayfield-Rothe Scale (1951) was used to measure job satisfaction as a subject. The result revealed that teachers’ age, gender, education, level of skills, types and duration of their employment have significant influence on job satisfaction. Keywords: Job satisfaction, Private university teachers.

A contribution to the amaranthine quarrel between true and average electrical mobility in the free molecular regime

Landau and Lipschitz's approach—termed here H&B due to the use of Happel and Brenner's slow rotation approximation—for calculating the average electrical mobility over all orientations of an ion in the free molecular regime is shown in this manuscript to be an invalid assumption for non-globular ions when a fixed electrical field is present. The reason behind the invalidity seems to be the confusion between average “settling” velocity (the calculation intended by H&B) and the average mobility (drag) in the direction of the field. When a missing orientation is taken into account by rotating the drag tensor, the average mobility obtained through Landau's approach coincides with well-known orientationally averaged Kinetic Theory Methods such as those of Mason and McDaniel (M&M). H&B's averaging approach, however, can be related to the true mobility displacement of the ion or, in other words, the displacement occurring in the direction of the velocity. This true mobility displacement only agrees with the average mobility displacement if ion velocity and electrical field have always the same direction, which only happens under special cases. Analytical and numerical calculations of collision cross-sections of linear and planar structures using a momentum transfer kinetic theory approach are chosen here as a means to prove that a single rotation of the drag tensor is sufficient to show agreement between both methods. A projected area approach is also used to prove the inadequacy of the H&B method

Group Chase and Escape with Conversion from Targets to Chasers

We are studying the effect of converting caught targets into new chasers in the context of the recently proposed `group chase and escape' problem. Numerical simulations have shown that this conversion can substantially reduce the lifetimes of the targets when a large number of them are initially present. At the same time, it also leads to a non-monotonic dependence on the initial number of targets, resulting in the existence of a maximum lifetime. As a counter effect for this conversion, we further introduce self-multiplying abilities to the targets. We found that the longest lifetime exists when suitable combination of these two effects is created.Comment: submitted for publicatio

No time machines in classical general relativity

Irrespective of local conditions imposed on the metric, any extendible spacetime U has a maximal extension containing no closed causal curves outside the chronological past of U. We prove this fact and interpret it as impossibility (in classical general relativity) of the time machines, insofar as the latter are defined to be causality-violating regions created by human beings (as opposed to those appearing spontaneously).Comment: A corrigendum (to be published in CQG) has been added to correct an important mistake in the definition of localit

Modeling of an Inverted Drift Tube for Improved Mobility Analysis of Aerosol Particles

A new mobility particle analyzer, which has been termed Inverted Drift Tube, has been modeled analytically as well as numerically and proven to be a very capable instrument. The basis for the new design have been the shortcomings of the previous ion mobility spectrometers, in particular (a) diffusional broadening which leads to degradation of instrument resolution and (b) inadequate low and fixed resolution (not mobility dependent) for large sizes. To overcome the diffusional broadening and have a mobility based resolution, the IDT uses two varying controllable opposite forces, a flow of gas with velocity v gas , and a linearly increasing electric field that opposes the movement. A new parameter, the separation ratio Λ = v drift /v gas , is employed to determine the best possible separation for a given set of nanoparticles. Due to the system’s need to operate at room pressure, two methods of capturing the ions at the end of the drift tube have been developed, Intermittent Push Flow for a large range of mobilities, and Nearly-Stopping Potential Separation, with very high separation but limited only to a narrow mobility range. A chromatography existing concept of resolving power is used to differentiate between peak resolution in the IDT and acceptable separation between similar mobility sizes

Health need and the use of alternative medicine among adults who do not use conventional medicine

<p>Abstract</p> <p>Background</p> <p>We hypothesize that a substantial portion of individuals who forgo conventional care in a given year turn to some form of alternative medicine. This study also examines whether individuals who use only alternative medicine will differ substantially in health and sociodemographic status from individuals using neither alternative medicine nor conventional care in a given year. To identify those factors that predict alternative medicine use in those not using conventional care, we employed the socio-behavioral model of healthcare utilization.</p> <p>Methods</p> <p>The current study is a cross-sectional regression analysis using data from the 2002 National Health Interview Survey. Data were collected in-person from 31,044 adults throughout the 50 states and the District of Columbia.</p> <p>Results</p> <p>19.3% of adults (38.3 million) did not use conventional care in a 12 month period, although 39.5% of these individuals (14.7 million) reported having one or more problems with their health. Of those not using conventional care, 24.8% (9.5 million) used alternative medicine. Users of alternative medicine had more health needs and were more likely to delay conventional care because of both cost and non-cost factors compared to those not using alternative medicine. While individual predisposing factors (gender, education) were positively associated with alternative medicine use, enabling factors (poverty status, insurance coverage) were not.</p> <p>Conclusions</p> <p>We found that a quarter of individuals who forgo conventional care in a given year turn towards alternative medicine. Our study suggests that the potential determinants of using only alternative medicine are multifactorial. Future research is needed to examine the decision process behind an individual's choice to use alternative medicine but not conventional medicine and the clinical outcomes of this choice.</p