Numerical Study of Hydrodynamics of Heavily Loaded Hard-Chine Hulls in Calm Water

Hard-chine boats are usually intended for high-speed regimes where they operate in the planing mode. These boats are often designed to be relatively light, but there are special applications that may occasionally require fast boats to be heavily loaded. In this study, steady-state hydrodynamic performance of nominal-weight and overloaded hard-chine hulls in calm water is investigated with computational fluid dynamics solver program STAR-CCM+. The resistance and attitude values of a constant-deadrise reference hull and its modifications with more pronounced bows of concave and convex shapes are obtained from numerical simulations. On average, 40% heavier hulls showed about 30% larger drag over the speed range from the displacement to planing modes. Among the studied configurations, the hull with a concave bow is found to have 5–12% lower resistance than the other hulls in the semi-displacement regime and heavy loadings and 2–10% lower drag in the displacement regime and nominal loading, while this hull is also capable of achieving fast planing speeds at the nominal weight with typical available thrust. The near-hull wave patterns and hull pressure distributions for selected conditions are presented and discussed as well.

Optical spectroscopy of Galactic field classical Be stars

ABSTRACT In this study, we analyse the emission lines of different species present in 118 Galactic field classical Be stars in the wavelength range of 3800–9000 Å. We re-estimated the extinction parameter (AV) for our sample stars using the newly available data from Gaia DR2 and suggest that it is important to consider AV while measuring the Balmer decrement (i.e. D34 and D54) values in classical Be stars. Subsequently, we estimated the Balmer decrement values for 105 program stars and found that ≈20 per cent of them show D34 ≥ 2.7, implying that their circumstellar disc are generally optically thick in nature. One program star, HD 60855 shows H α in absorption – indicative of disc-less phase. From our analysis, we found that in classical Be stars, H α emission equivalent width values are mostly lower than 40 Å, which agrees with that present in literature. Moreover, we noticed that a threshold value of ∼10 Å of H α emission equivalent width is necessary for Fe ii emission to become visible. We also observed that emission line equivalent widths of H α, P14, Fe ii 5169, and O i 8446 Å for our program stars tend to be more intense in earlier spectral types, peaking mostly near B1-B2. Furthermore, we explored various formation regions of Ca ii emission lines around the circumstellar disc of classical Be stars. We suggest the possibility that Ca ii triplet emission can originate either in the circumbinary disc or from the cooler outer regions of the disc, which might not be isothermal in nature.

Computerized Fluid Dynamic Study of Parameter Effects on the Performance of Coaxial Propellers

The computerized fluid dynamic (CFD) analysis was performed for 1.8 m diameter coaxial propellers to be applied to the multi-copter type Personal Air Vehicle (PAV) having conceptually 600 kg of Maximum Take-Off Weight (MTOW). Methods/Statistical analysis: Using the commercial CFD program STAR-CCM+ (13.03.11), the coaxial propellers were analyzed at the same RPM under the steady state condition. The three-dimensional Compressible Reynolds Mean Navier-Stokes equation was applied and the Moving Reference Frame (MRF) technique was used. With the optimum single pitch angle of upper propeller, the lower propeller’s pitch was changed for the varying propeller spacing to identify the performance variation and the interference effect. The lower propeller has to be different pitch setting other than the upper propeller’s optimum pitch angle because of the interfered flow effect between propellers. The propeller spacing is not so sensitive to efficiency if the spacing is more than 0.25 of propeller diameter. Study shows that the identified pitches and spacing of coaxial propellers are essential for designing the configuration and control of multi-copter type PAV which uses variable pitch propellers for safety and efficiency.

PROGRAM STAR ( SEHAT TANPA ASAP ROKOK ) SEBAGAI PENYULUHAN DAMPAK BURUK MEROKOK BAGI PEROKOK PASIF DI DESA JEBRES, KECAMATAN JEBRES, SURAKARTA

The danger and bad effects of smoking on health have been felt by many active and passive smokers. However, awareness of the dangers of smoking in Desa Jebres is still low. Therefore, I conducted an education program on the dangers of smoking in Jebres Village, Jebres District, Surakarta. This program is given the name STAR (Sehat Tanpa Asap Rokok), an educational program about the dangers of smoking for passive smokers in the village of Jebres. The program consists of counseling through electronic social media, and the distribution of pamphlets. In general, the public does not understand the danger that is caused by smoking behavior both for themselves (active smokers) and other people (passive smoking). This is seen from the results of a survey that I conducted on several family heads in the village of Jebres. It was found that the majority of the people (70%) were still smoking in their house near family members. Therefore, we educate about the dangers of smoking for passive smokers. The intervention results show that there is increased awareness of the dangers of cigarettes to themselves and to others who are exposed to cigarette smoke

The Policy Brief Assignment: Transferable Skills in Action in a Community-Engaged Writing Project

The policy brief assignment in my capstone course in professional writing was designed as a community-engaged project in partnership with a nonprofit organization whose mission is to grow Reading, Pennsylvania's economy. The assignment was intended to do real work in the world: the nonprofit's director, a city council member, and an outreach manager for the city of Reading plan to use the policy briefs to convince Reading's City Council to adopt the recommended policies to enhance citizen participation and representation in local governance and to address deficiencies identified through the STAR Community Rating System(r) (STAR), the nation's leading sustainability framework and certification program (STAR 2016). I welcomed the collaboration and designed the assignment with the goal that students would experience what writing faculty always tell them: fundamental concepts in composition and rhetoric/writing studies are operational in the workplace, and understanding writing and communication rhetorically opens up possibilities for them to enter diverse and unfamiliar writing contexts. Students successfully researched, synthesized, organized, and clearly communicated information in a content area and genre new to them. They presented their policy briefs in written and electronic form to the community partners and explained their work in oral presentations. It was an exciting, nerve-wracking, and challenging endeavor, and, as I will describe, the periods of dissonance led to the best learning experiences--for students and for me.

Romanian Public-Funded Research And Development Activities In The Space Sector

Romania achieved full membership within ESA (European Space Agency) in 2011 and is actually involved in several European flagship space programmes. The “National Strategy for Space and Related Fields” is a strategic project funded through the Romanian Space Technology and Advanced Research Program (STAR), which is implemented by a consortium coordinated by IAROM S.A. One of the project goals is to identify national space- related technological capabilities and possible niches for Romania within the European space industry, as well as to identify cooperation opportunities within the mandatory and optional ESA programs. This paper presents an overview of the areas of expertise covered by projects contracted in 2012 and 2013 in the framework of the national space research and development programme. The paper does not cover industrial space contracts since they contain sensitive information.

Investigation of Riding Position Effects on Time-Trial Bicycle Drag Coefficient at Different Yaw Angles

Time-trial bicycle racing is highly influenced by aerodynamics, perhaps more so than any other form of bicycle racing. Companies competing in this class of racing spend millions of dollars trying to optimize the geometry of the bicycles and the gear each rider wears in order to reduce aerodynamic drag. The idea behind this project was to investigate other ways to optimize the aerodynamic efficiency of the rider, considering that the rider contributes the majority of the drag force of the bicycle-rider system. A large contributor to drag is the frontal area of the object of interest (a silhouette of the object in the fluid flow direction). This illustrates how much the rider’s body contributes to overall drag. If small riding adjustments could be made to the rider’s body during riding, drag may be significantly reduced. This idea and the fact that the direction of wind impacting the rider can vary influenced the concept of this project. It was hypothesized that adjusting the time-trial handlebars on the bicycle to place one of the rider’s hands further aft than the other would influence the upper body to rotate slightly. This could then reduce the frontal area of the rider in the wind direction, therefore reducing the aerodynamic drag. To simulate this situation, a non-contact 3-D digitizer was used to scan a rider aboard a bicycle in a normal riding position and in the above-mentioned, asymmetric position. This 3-D scan was then imported into the computational fluid dynamics (CFD) program Star-CCM+ and several simulations were run. Each of the two riding positions was simulated at differing yaw angles, ranging from −45° to 45°. The initial simulations seem to prove the theory as the asymmetrical riding position experiences decreased drag at significant yaw angles while the normal riding position does not. These results are encouraging and it is desired to continue refinement of the scanning and simulation methods as well as to validate these findings in a wind tunnel.

EBZ160 Star Wheel Boring Machine Loading Mechanism Optimization Analysis

In order to ensure the boring machine to work, star wheel loading mechanism must have good loading properties. The force of star wheel of EBZ160 loading mechanism is analyzed based on the creation of three-dimensional model of star wheel by using PRO/E software. Static analysis is done by importing the three-dimensional model of the star wheel in ansys. Checking the strength of the program star wheel. Based on the meet of the strength of the star wheel, topology optimization is done by using the OC method. The results obtained from topology optimization can be seen, basically meet the requirements of this program the amount of material is decreased by 20kg than before. The theoretical basis of improving star wheel design and improving performance is obtained.

Technology Change and Online Community Development

Online communities are increasingly seen to display the same features accepted as characteristic of communities based on face-to-face interaction. Among the characteristics of “real,” “normal” communities is the ability to grow and thrive by evolving and adapting to, for example, changes in technology and infrastructure. Our experience in online gaming communities also demonstrates this same ability to evolve and adapt to technological and infrastructural changes. One online community that began in 1991 and continues to “live long and prosper” began in conception as a role-playing game called Starfleet and is now described as a shared fiction or collaborative writing group. Set in a fictional universe based on that of the television program “Star Trek: The Next Generation,” this group moved from the Prodigy online service onto Usenet in 1994 (it is still known by its newsgroup name, “alt.starfleet.rpg”), and by 2000 had established a Web-based Yahoo! Group (http://groups.yahoo. com/group/starfleet-rpg/), which continues to be its means of functional interaction. Each of these hosting venues brought with it changes in the means (posts, direct e-mails, Web pages) by which game or collaborative writing activities were conducted. Parallel to these were changes in the rules, policies, and practices of the community. Even the nature and content of the social interactions of the members of the community changed in fundamental ways as its technological manifestation did so.