Optimal Design of V-Shaped Fin Heat Sink for Active Antenna Unit of 5G Base Station

The active antenna unit (AAU) is one of the main parts of the 5G base station, which has a large size and a high density of chipsets, and operates at a significantly high temperature. This systematic study presents an optimal design for the heat sink of an AAU with a V-shaped fin arrangement. First, a simulation of the heat dissipation was conducted on two designs of the heat sink – in-line and V-shaped fins – which was validated by experimental results. The result shows that the heat sink with V-shaped fins performed better compared to conventional models such as heat sinks with in-line fins. Secondly, computational fluid dynamics (CFD) and the Lagrange interpolation method were applied to find out an optimal set of design parameters for the heat sink. It is worth noting that the optimal parameters of the orientation angle and fin spacing considerably affected the heat sink’s performance.  

Optimal Design of V-Shaped Fin Heat Sink for Active Antenna Unit of 5G Base Station

The active antenna unit (AAU) is one of the main parts of the 5G base station, which has a large size and a high density of chipsets, and operates at a significantly high temperature. This systematic study presents an optimal design for the heat sink of an AAU with a V-shaped fin arrangement. First, a simulation of the heat dissipation was conducted on two designs of the heat sink – in-line and V-shaped fins – which was validated by experimental results. The result shows that the heat sink with V-shaped fins performed better compared to conventional models such as heat sinks with in-line fins. Secondly, computational fluid dynamics (CFD) and the Lagrange interpolation method were applied to find out an optimal set of design parameters for the heat sink. It is worth noting that the optimal parameters of the orientation angle and fin spacing considerably affected the heat sink’s performance.  

Synthesis and Application of Pheromones for Integrated Pest Management in Vietnam

The negative impacts of conventional pesticides on health, environment, and organisms have involved strong development of integrated pest management (IPM) strategies. The use of insect pheromones becomes an effectively alternative selection in agricultural and forest pest control. Pheromone researches in Vietnam started in the last few decades and in addition to technical factors, recent achievements in the Vietnamese agriculture have an important direct link to the pheromone developments. In this chapter, we review the pheromone researches related to synthesis and field trials of several especial insect pheromones, in which Vietnamese scientists have mainly participated or collaborated with foreign research groups. First, we will discuss an overview of popular insect pheromones in Vietnam, a lot of species of which are also found around the world, as an important reference for scientists who would have especial consideration in this field. Further, synthetic routes of pheromones are summarized with various structures including chiral, racemic, mono- and poly-olefinic pheromones where some schemes have become standard methodologies for synthesis of similar structural compounds. Finally, field evaluations of the pheromones of numerous species are discussed in detail

CFD results on hydrodynamic performances of a marine propeller

In this work, the commercial Computational Fluid Dynamics (CFD), ANSYS-Fluent V.14.5 has been used to illustrate the effects of rudder and blade pitch on hydrodynamic performances of a propeller. At first, the characteristic curves of a container ship propeller are computed. Then, effects of rudder on hydrodynamic performances of the propeller in the both cases of the propeller with and without rudder have been investigated. The relationships between the blade pitch angle and the hydrodynamic performances of the selected referent propeller in this work having designed conditions as diameter of 3.65 m; speed of 200 rpm; average pitch of 2.459 m and the boss ratio of 0.1730. Using CFD, the characteristic curves of the marine propeller, pressure distribution, velocity distribution around propeller and the efficiency of the propeller have been shown. From the obtained results, the effects of rudder and blade pitch angle on hydrodynamic performances of the propeller have been evaluated

A Survey on Some Parameters of Beef and Buffalo Meat Quality

A survey was carried out on 13 Vietnamese Yellow cattle, 14 LaiSind cattle and 18 buffalos in Hanoi to estimate the quality of longissimus dorsi in terms of pH, color, drip loss, cooking loss and tenderness at 6 different postmortem intervals. It was found that the pH value of longissimus dorsi was not significantly different among the 3 breeds (P>0.05), being reduced rapidly during the first 36 hours postmortem, and then stayed stable. The value was in the range that was considered to be normal. Conversely, the color values L*, a* and b* tended to increase and also stable at 36 hours postmortem, except that for LaiSind cattle at 48 hours. According to L* scale, the meat of Yellow and LaiSind cattle met the normal quality but the buffalo meat was considered to be dark cutters. The tenderness of longissimus dorsi was significantly different among the breeds (P<0.05). The value was highest at 48 hours and then decreased for LaiSind and buffalo, but for Yellow cattle the value decreased continuously after slaughtering In terms of tenderness buffalo meat and Yellow cattle meat were classified as “intermediate”, while LaiSind meat was out of this interval and classified as “tough”. Drip loss ratio was increased with the time of preservation (P<0.05). The cooking loss ratio was lowest at 12 hours and higher at the next period, but there was no significant difference among the periods after 36 hours postmotem.Peer reviewe

Kinematic and dynamic modelling for a class of hybrid robots composed of m local closed-loop linkages appended to an n-link serial manipulator

Recently, more and more hybrid robots have been designed to meet the increasing demand for a wide spectrum of applications. However, development of a general and systematic method for kinematic design and dynamic analysis for hybrid robots is rare. Most publications deal with the kinematic and dynamic issues for individual hybrid robots rather than any generalization. Hence, in this paper, we present a novel method for kinematic and dynamic modelling for a class of hybrid robots. First, a generic scheme for the kinematic design of a general hybrid robot mechanism is proposed. In this manner, the kinematic equation and the constraint equations for the robot class are derived in a generalized case. Second, in order to simplify the dynamic modelling and analysis of the complex hybrid robots, a Lemma about the analytical relationship among the generalized velocities of a hybrid robot system is proven in a generalized case as well. Last, examples of the kinematic and dynamic modelling of a newly designed hybrid robot are presented to demonstrate and validate the proposed method

Structure elucidation off seven steroids from Sinularia conferta.

Seven steroids were isolated from the methanol extract of the soft corals Sinularia conferta. These steroids were elucidated as 7a-methoxyergosta-5,24(28)-diene-3b-ol (1), ergosta-5-ene-3β,7α-diol (2), 3β,7α-dihydroxyergosta-5,24(28)-diene (3), 3β-hydroxyergosta-5,24(28)-diene-7-one (4), ergosta-24(28)-ene-3β,5α,6β-triol-6-acetate (5), ergosta-24(28)-ene-3β,5α,6β-triol (6), and ergosta-3β,5α,6β-triol (7) by 1D and 2D-NMR experiments and comparison with reported data. Keywords. Sinularia conferta, Alcyoniidae, soft coral, steroid

Probabilistic Schema Covering

Schema covering is the process of representing large and complex schemas by easily comprehensible common objects. This task is done by identifying a set of common concepts from a repository called concept repository and generating a cover to describe the schema by the concepts. Traditional schema covering approach has two shortcomings: it does not model the uncertainty in the covering process, and it requires user to state an ambiguity constraint which is hard to define. We remedy this problem by incorporating probabilistic model into schema covering to generate probabilistic schema cover. The integrated probabilities not only enhance the coverage of cover results but also eliminate the need of defining the ambiguity parameter. Both probabilistic schema covering and traditional schema covering run on top of a concept repository. Experiments on real-datasets show the competitive performance of our approach

SOME METEO - HYDRO - DYNAMICAL FEATURES IN MEKONG RIVER MOUTH AREA

This paper provides some meteo-hydro-dynamical features in Mekong River Mouth area which were based on statistical results from longtime measurement data such as wind, wave, sea water level, and river discharge. Study results show that distribution features of wind and wave characteristics are corresponding to seasonal variation. Predominant wind and wave directions during NE Monsoon period is NE, and in W, SW directions during SW Monsoon period. NE Monsoon period is from November to April (strongest in December and January), SW Monsoon period is from June to September (strongest in August). During NE Monsoon period the wind velocity and wave height were higher than that of SW Monsoon period. Variation of SWL at Vungtau Station shows that the tide is semi-diurnal with maximum value occurred during NE monsoon period (highest in November), and minimum value occurred during SW Monsoon period (lowest in June). Variation of river discharge is similarly at two stations (Mythuan and Cantho). During flood season (from July to December) average monthly discharge was ranged from 4,000 to 15,800 m3/s. During dry season (from January to May) average monthly discharge at both stations was less than 4,000 m3/s. Statistical data show that Mekong River Mouth area is a region of strong and complicated hydro-dynamical interaction processes between river and sea. Key words: Monsoon, North-East (NE), South-West (SW), Sea Water Level (SWL), River discharge, Mekong River