Cyclic Experiments and Global Buckling Design of Steel-Angles-Assembled Buckling-Restrained Braces

Compared with traditional BRB, the steel-angles-assembled buckling-restrained brace (SAA-BRB) is an innovative BRB with light-weight, accurate control of the geometrical dimensions, easy installation and convenient disassembly. The SAA-BRB is composed of an external restraining system and a cruciform-sectional inner core. The external restraining system is assembled by four steel angles with the connection of high-strength bolts, and the spacers are installed between the inner core and the restraining system. In this study, the hysteretic behavior of SAA-BRB was investigated by experiments and finite element (FE) simulations. Firstly, three SAA-BRB specimens with different restraining ratios were tested under cyclic loads to investigate the hysteretic performance. It was found that all specimens exhibited stable responses and satisfactory energy-dissipating capabilities during the whole loading process. Then, a refined FE model was established, and its validity in predicting the hysteretic responses of SAA-BRB was verified by the experiments. Moreover, based on the yielding criteria of the outmost fiber for the restraining member section, a design formula for the restraining ratio requirements to avoid global buckling of the SAA-BRB was deduced. Finally, extensive parametric analysis was conducted to verify the accuracy of the design formula by changing the geometric dimensions (the restraining ratio) of models. It was found that the proposed formula for the restraining ratio requirement could lead to a conservative prediction with reasonable accuracy, thus providing valuable references for global buckling design of SAA-BRBs in engineering practice.

​Standardization of Cold Solvent Extraction Parameters for Natural Red Pigments

Background: Selecting an appropriate extraction technique and optimization of extraction conditions must be done to improve the efficiency and productivity of natural colorant. Methods: Flesh and peels of four different raw materials viz., beetroot, carrot, pomegranate and grape were extracted independently using 100% ethyl alcohol using cold solvent extraction method adopting 1: 1 and 1: 2 w/v solid to solvent ratio for 24 and 48 hrs, forming 8 treatments replicated thrice in three factorial CRD. The collected extracts were evaporated at 60oC; per cent yield and pigment content were calculated. Result: Extract yield and pigment content were significantly influenced by raw material, solid to solvent ratio and duration of extraction. Extract yield was higher in flesh of carrot and beetroot as well as in peels of grape and pomegranate. Anthocyanin content in grape and pomegranate and betalain content in beetroot were high in peel where as β-carotene content was higher in carrot flesh extract. Per cent yield and pigment content increased with increased duration of extraction and solid to solvent ratio. Requirement of more solvent and longer extraction time are the drawback of conventional extraction methods and there is a growing demand for non-conventional techniques to enhance yield and maintain pigment stability.

Unprotected water sources and low latrine coverage are contributing factors to persistent hotspots for schistosomiasis in western Kenya

Background Evidence indicates that whereas repeated rounds of mass drug administration (MDA) programs have reduced schistosomiasis prevalence to appreciable levels in some communities referred to here as responding villages (R). However, prevalence has remained high or less than anticipated in other areas referred to here as persistent hotspot villages (PHS). Using a cross-sectional quantitative approach, this study investigated the factors associated with sustained high Schistosoma mansoni prevalence in some villages despite repeated high annual treatment coverage in western Kenya. Method Water contact sites selected based on observation of points where people consistently go to collect water, wash clothes, bathe, swim or play (young children), wash cars and harvest sand were mapped using hand-held smart phones on the Commcare platform. Quantitative cross-sectional surveys on behavioral characteristics were conducted using interviewer-based semi-structured questionnaires administered to assess water usage/contact patterns and open defecation. Questionnaires were administered to 15 households per village, 50 pupils per school and 1 head teacher per school. One stool and urine sample was collected from 50 school children aged 9–12 year old and 50 adults from both responding (R) and persistent hotspot (PHS) villages. Stool was analyzed by the Kato-Katz method for eggs of S. mansoni and soil-transmitted helminths. Urine samples were tested using the point-of-care circulating cathodic antigen (POC-CCA) test for detection of S. mansoni antigen. Results There was higher latrine coverage in R (n = 6) relative to PHS villages (n = 6) with only 33% of schools in the PHS villages meeting the WHO threshold for boy: latrine coverage ratio versus 83.3% in R, while no villages met the girl: latrine ratio requirement. A higher proportion of individuals accessed unprotected water sources for both bathing and drinking (68.5% for children and 89% for adults) in PHS relative to R villages. In addition, frequency of accessing water sources was higher in PHS villages, with swimming being the most frequent activity. As expected based upon selection criteria, both prevalence and intensity of S. mansoni were higher in the PHS relative to R villages (prevalence: 43.7% vs 20.2%; P < 0.001; intensity: 73.8 ± 200.6 vs 22.2 ± 96.0, P < 0.0001), respectively. Conclusion Unprotected water sources and low latrine coverage are contributing factors to PHS for schistosomiasis in western Kenya. Efforts to increase provision of potable water and improvement in latrine infrastructure is recommended to augment control efforts in the PHS areas.

Characteristics of gas-driven fan propulsion system for fixed-wing vertical take-off and landing aircraft

As a propulsion system for vertical take-off and landing (VTOL) aircraft, the gas-driven fan propulsion system has received some attention in recent years due to its simple mechanical structure and good performance. During the operation of the propulsion system, the core turbofan exhaust is directed to the tip turbine to drive the ducted fan to obtain thrust, and the louvered vector exhaust device is used to achieve lift/thrust switching. However, due to the linkage characteristics of the guide vanes of the exhaust device, the exhaust area will gradually change with the deflection of the guide vanes. This may cause uncertain effects on the system. Besides, considering the development cost of the propulsion system, it is necessary to clarify whether the core turbofan needs to be redesigned based on the characteristics of the system. Further, the transitional performance (VTOL to flight) of the propulsion system also needs to be studied. To this end, this study established an overall model of the gas-driven fan propulsion system combined with the characteristics of the core turbofan to analyze these problems. The results indicate that the louvered vector exhaust device can well match the gas-driven fan propulsion system. And when the propulsion system is composed, the gas-driven fan will not significantly affect the operation characteristics of the core turbofan. Besides, the preliminary analysis shows that the gas-driven fan propulsion system can meet the power requirements of the transition state of the fixed-wing VTOL aircraft. And the characteristics of the propulsion system may make the take-off thrust-weight ratio requirement of the fixed-wing VTOL aircraft be as low as 1.1.

Design and optimization for UAV-enabled two-way relaying system with SWIPT

In this paper, we investigate the resource allocation scheme for an unmanned-aerial-vehicle-enable (UAV-enabled) two-way relaying system with simultaneous wireless information and power transfer (SWIPT), where two user equipment exchange information with the help of UAV relay and harvest energy through power splitting (PS) scheme. Under the transmission power constraints at UEs and UAV relay, a non-convex intractable optimization problem is formulated which maximizes the sum retained energy of two UEs while satisfying the minimum signal-to-noise ratio requirement. We decouple the complicated beamforming and PS factor optimization problem into three solvable subproblems and propose an efficient alternating optimization scheme. Subsequently, in order to reduce the complexity, a robust scheme based on generalized singular value decomposition (GSVD) is designed. Finally, numerical results verify the robustness and effectiveness of the two proposed schemes.

A novel planetary thread roller bearing: Design and analysis of load characteristic

A novel planetary thread roller bearing (PTRB) was proposed in this paper based on Herz theory combined with multiple principles (e.g. equivalent steel ball, multi-point meshing and power dividing). A significant improvement in load-carrying capacity, comparing the current bearing, was achieved and thus providing a new option for the advanced equipment with high thrust-to-weight ratio requirement. The newly proposed PTRB exhibited a 83 % increase in dynamic axial load rating while a comparable static axial load rating comparing with the thrust ball bearing with a comparable size. In addition, the relationship between friction torque and bearing rotating speed, contact point number and axial load was discussed. It was found that, given a proper installation space, increasing the thread roller number could not only significantly improve the axial load rating of PTRB, but also reduce the friction torque. Furthermore, the working efficiency of the new PTRB was constantly higher than 97 %. A self-degradation operation was achieved by the system when some thread rollers were stuck, which improved the system fault tolerance. Finally, friction torque tests were performed on the self-developed test instrument. The results showed a good agreement with the theoretical analysis.

Effect of Dietary Standardized Ileal Digestible Arginine to Lysine Ratio on the Reproductive Performance, Plasma Free Amino Acid Profile, and Colostrum Composition in Gestating Sows

Background: The objective of the present study was to determine the optimal standardized ileal digestible arginine to lysine (SID Arg: Lys) ratio on the reproductive performance, plasma free amino acids and biochemical parameters of sows during gestation , as well as colostrum compositions and performance of their offspring litter . Methods: A total of 174 multiparous sows (3+ parity,Landrace × Large white ) were randomly allocated to five treatment groups with different dietary SID Arg: Lys ratios (0.91, 1.02, 1.14, 1.25 and 1.38) by modifying the supplementation of Arg or alanine (Ala) for isonitrogenous equilibrium. All diets were formulated with the same composition levels including DE at 3.14 Mcal/kg and SID Lys at 0.64%. The reproductive performance of sows during gestation and lactation and the performance of offspring litters during lactation were evaluated. Blood samples were obtained on days 90 and 110 of gestation for analyses of plasma biochemical indexes and free amino acids, and colostrum samples were collected for determination of the composition. Results: The results showed that increasing the dietary SID Arg: Lys ratio increased litter size alive linearly ( P =0.001) and quadratically ( P =0.001), and decreased the number of stillborns linearly ( P <0.001) and quadratically ( P <0.001), and decreased the mummified size quadratically ( P =0.033). The birth weight variation of born alive was linearly ( P= 0.002) and quadratically ( P =0.008) reduced by increasing the dietary SID Arg: Lys ratio. The broken-line regression analysis indicated that the optimal SID Arg: Lys ratio requirement for gestating sows to maximize the litter size alive was 1.25. Birth intervals were decreased linearly ( P =0.025) and quadratically ( P =0.013) with increasing the dietary SID Arg: Lys ratio. There were linear and quadratic increases ( P <0.05) in the concentrations of colostrum compositions including non-fat solid, total solid, protein, and energy by increasing dietary SID Arg: Lys ratio. The plasma nitric oxide (NO) and total protein in serum were increased linearly as dietary SID Arg: Lys ratio increased. Similarly, sows feed the diet with higher SID Arg: Lys ratio significantly increased the concentrations of plasma arginine in sows at day 90 of gestation and ornithine ( P <0.05). Conclusion: Collectively, the current study indicated that increasing the dietary SID Arg: Lys ratio during gestation resulted in the increase of litter size alive, reduction of birth intervals, and improvement of colostrum composition. The requirement of optimal SID Arg:Lys ratio for gestating sows to maximize the litter size alive was 1.25 using a linear broken-line model.

Design and Optimization for UAV-Enabled Two-Way Relaying System with SWIPT

In this paper, we investigate the resource allocation scheme for an unmanned-aerial-vehicle-enable (UAV-enabled) two-way relaying system with simultaneous wireless information and power transfer (SWIPT), where two userequipment exchange information with the help of UAV relay and harvest energythrough power splitting (PS) scheme. Under the transmission power constraintsat UEs and UAV relay, a non-convex intractable optimization problem isformulated which maximizes the sum retained energy of two UEs while satisfying the minimum signal-to-noise ratio requirement. We decouple the complicated beamforming and PS factors optimization problem into three solvable subproblems and propose an efficient alternating optimization scheme. Subsequently, in order to reduce the complexity, a robust scheme based on generalized singular value decomposition (GSVD) is designed. Finally, numerical results verify the robustness and effectiveness of two proposed schemes.

Topology Optimization of Frame of the Rack System

Integration of the Electronics modules in the rack system has been very challenging and critical in nature. The functionality of the electronics module is of prime importance for the operation on any system or subsystem. In many cases where these electronics systems housed in a rack system which in turn mounted in aircraft fuselage make functioning of the system more severe. This paper deals with design optimization of frame of rack structure in line with increasing demand of more robust and light structure with features of high stiffness and structural integrity. Aerospace industries employ topology , size and shape optimization technique and have reported significant structural performance gains as a result ,This report deals with the topology optimization of frame of rack structure has been performed using OptiStruct software. The main objective is to find the optimal topology of frame of the rack. The rack structure has undergone the first level of optimization, in other word it is called finite element analysis with inertia loading condition which presents the stress contour with varying stress level, the stress contour highlight the maximum and minimum stress level in the structure which gives the first level of information about the material requirement within the structure. Topology optimization being the part of the structural optimization is the extended domain of the structural analysis where optimum placement of the material in the design space is the prime focus. The design space is a geometrical space where material alteration is effected to achieve the design objective. Topology optimization problems utilize the firmest mathematical basis, to account for improved weight-to-stiffness ratio and perceived aesthetic appeal of specific structural forms, enabling the Solid Isotropic Material with Penalization (SIMP) technique. Structural topology optimization is a technique for finding the optimum number, location and shape of opening with in the given design space of the rack structure to the series of loads and the boundary conditions. A range of topology of rack frame is obtained by setting varying the target volume fraction and an optimum topology of the frame is selected by satisfying stress to weight ratio requirement and manufacturing constraint.