Applied Mechanics and Materials Vol. 145

Abstract: Polysaccharides extracted from fruiting body and mycelia of higher fungi have been found to show various biological activities. Traditionally, these polysaccharides are manufactured by the hot water extraction method. Low polysaccharide yield is the disadvantage of this method. This paper reports the optimal conditions to manufacture polysaccharide with high-yield from Hypsizigus marmoreus mycelia using enzymatic hydrolytic extraction method. Neutral protease was selected as the most cost efficient among six enzymes. The uniform design was further conducted to optimize the enzymatic hydrolytic extraction conditions, and a regression model was constructed to predict polysaccharide yield. The optimized procedures was that 2% (w/w) of neutral protease was added into hydrolytic solution and incubated for 4 h at 43°C, then extracted one time at 100°C for 1 h. Under optimized procedures, the measured polysaccharide yield was 15.73±0.15 (mg/g), which was very close to the predicted value of 16.65 (mg/g). The results validated the accuracy of the regression model and the optimized procedure. When following the optimized procedures, polysaccharide yield was raised 75.0% over that before optimization, and increased by 122.5% and 104.8% over hot-water extraction and microwave assisted extraction methods respectively. This was the first study to apply uniform design for optimizing high yield manufacture of mycelia polysaccharides by enzymatic hydrolytic extraction. We concluded that enzymatic hydrolytic extraction was a simple, high yield method to manufacture polysaccharides from mushroom mycelia and might be used widely in polysaccharide-derived functional foods production.

Abstract: This research provides an improvement for the method of Douglas to determine pentose and hexose sugars in mixed sugars. Specific absorption wave of 553 nm for pentose derivatives and 408 nm for hexose derivatives are selected for determination, and the interference from pentose sugar to hexose sugar is corrected with multiple linear regression method. The results show that the interference from pentose sugar is reduced greatly after multiple linear regression calibration; the error is lower than 5.0 %. The experimental results show a satisfying precision and accuracy, with a recovery range from 95.1 % to 106.8%. This method is suitable for simultaneously rapid determination of pentose and hexose sugars in practical application.

Abstract: The vehicular ad hoc network (VANET) has made significant progress in recent years, attracting a lot of interest from academia and the industry. VANET involves vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications based on a wireless network. V2I refers to the communication between vehicles and infrastructure of roadside unit (RSU), e.g., a base station and access point (AP) connected to the Internet. V2V refers to the direct or multi-hop communications among vehicles in VANET. V2V is efficient and cost effective owing to its short range bandwidth advantage and its ad hoc nature. V2V communications are enabling technologies that enhance the driver’s awareness of nearby vehicular traffic, leading to improved traffic safety and efficiency. The V2V mode provides a communications platform between road vehicles (cars, bikes, scooters, motorcycles, trucks, etc.) without requiring a central control unit. Safety-related V2V applications are enabled via an integrated early warning mechanism. To facilitate safe driving, we propose an Intelligent Vehicular Warning System (IVWS) that sends an immediate warning message in the event of an accident. According to V2V communications, the other cars or vehicles could have enough time to avoid the accident and make an appropriate decision such as slow down, stop, and detour after receiving the urgent warning messages. Furthermore, the local CMS (Changeable Message Sign) can show the accident information for neighbor vehicles when receiving the warning message. To achieve experimental architecture with our proposed IVWS, the robot vehicles have been designed to simulate vehicles on the road. Besides, vehicles also apply ZigBee wireless interface to communicate with each other. The experiment has shown that our proposed intelligent system can initially provide message display and safety driving for vehicles when traffic accident occurred.

Abstract: We consider a call center whose customers can be classified into two types depending on their tendency towards waiting in the queue. A customer of type A waits in the queue, if necessary, until he gets served. On the other hand, a type B customer is assumed to be impatient and he does not join the queue and leaves the call center immediately if there is no server available. There are well known formulas for calculating the service levels when a call center serves only one customer type; Erlang delay formula and Erlang loss formula for type A and type B customers, respectively. Hence, there is no such simple analytic result for computing service levels when a call center handles both customer types together. In this paper we suggest and compare several approximation methods to calculate type A and B customer service levels for a call center serving both customer types. Numerical experiments show that one of the methods suggested in this paper approximates closely the actual service level especially when the call center provides high level of service

Abstract: A passive magnetic thrust bearing for a small vertical wind generator system is considered in this paper. The passive magnetic bearing is designed to reduce the axial load of the rotor system. The load capacity of the passive magnetic bearing is analyzed by finite element analysis software. From the simulation results, a suitable solution for the passive magnets of the test wind generator system is verified to be 225.6N with about a 2mm air gap. The experiment results show that a wind generator system with the additional passive magnetic bearing can start at a lower wind speed and transfers more power to the generator. The proposed hybrid bearing system can increase efficiency by 20%~50%, as compared with a traditional system supported by roller bearings at the same wind speed.

Abstract: Mushrooms have been highly valued as tonic foods and herb remedies since ancient times, and have been increasingly concerned because of their biological and pharmacological activities recognized through recent scientific research. Antitumor, antioxidant and ACE inhibitory activities in vitro of liquid fermentation materials from Ramaria botrytoides, Lyophyllum decastes and Mycoleptodonoides aitchisonii were investigated in this study. Water extracts from fermented mycelia and supernatant materials were used to measure their antitumor effect by MTT assay, antioxidant capacity by kit, and ACE inhibitory activity by RP-HPLC. Results showed that mycelia extracts from Ramaria botrytoides has significantly higher anti-proliferative effect on human HCC cell line SMMC7721 (IC50=0.284±0.005mg/ml, p<0.001). Total antioxidant activity of mycelia extracts of Ramaria botrytoides (0.711±0.053U/mg), inhibitory effect of mycelia extracts of Mycoleptodonoides aitchisonii on hydroxyl radical (86.153±1.763U/mg) and superoxide anion radical (7.363±0.280 U/g) were higher than others significantly (p<0.001). ACE inhibitory activity of mycelia extracts of Lyophyllum decastes (IC50=1.637±0.057mg/ml) was significantly higher than others (p<0.001). Results demonstrated that liquid fermented mycelium of Ramaria botrytoides was potent source of natural compound with antitumor and antioxidant potential. Mycelium of Lyophyllum decastes was potent source of natural compound with ACE inhibitory activity.

Abstract: In 2008, Bindu et al. proposed an improvement to Chien et al.'s remote password authentication scheme preserving user anonymity, and has asserted that the scheme is secure against replay attack, guessing attack, insider attack and man-in-the-middle attack, etc. However, in this paper, we have shown that Bindu et al.'s scheme is still insecure against man-in-the-middle attack and password guessing attack, and does not provide user anonymity. Also, we propose an improved scheme to withstand these weaknesses, while preserving their merits, even if the secret information stored in the smart card is revealed. As a result of analysis, the proposed scheme is secure against user impersonation attack, server masquerading attack, password guessing attack and does provide user anonymity. And we can see that the proposed scheme is relatively more effective than Bindu et al.'s scheme.

Abstract: In this paper, a hybrid method combining rough set and shared nearest neighbor algorithms is proposed for data clustering with non-globular shapes. The rough k-means algorithm is based on the distances between data and cluster centers. It partitions a data set with globular shapes well, but when the data are non-globular shapes, the results obtained by a rough k-means algorithm are not very satisfactory. In order to resolve this problem, a combined rough set and shared nearest neighbor algorithm is proposed. The proposed algorithm first adopts a shared nearest neighbor algorithm to evaluate the similarity among data, then the lower and upper approximations of a rough set algorithm are used to partition the data set into clusters.

Abstract: In the last decade, nanosized phosphors had attracted a lot of interest, no matter in light emitting layers or thermal remove materials. Many methods had been investigated to synthesize nanosized phosphors, but they usually need expensive cost and complicated procedures, furthermore they resulted in the difficulties in mass production. In our work, chemical co-precipitation was applied to prepare YAG:Ce precursor. Then, the mixed precipitation was heated to 900°C with air in the furnace. After 1 hour, the synthesis was completed. From TEM images, the average particle size is about 40 nm and all XRD diffraction peaks of phosphor powders were consistent to JCPDS data of YAG. Photoluminescence spectra show the nanosized YAG:Ce phosphor synthesized at 1000°C possessed the strongest photoluminescence intensity at wavelength 540 nm. From photoluminescence excitation spectra, the strongest absorption peak was observed at wavelength 460 nm in all samples. At synthesis temperature 1000°C, YAG with 0.5% Ce³⁺ was observed to emit the strongest yellow light. It is believed our synthesis can provide an easy and low-cost choice to synthesize YAG:Ce nanophosphors at high temperature.

Abstract: Biomass gasification is influenced by many factors, such as temperature, air equivalent ratio, steam/carbon mole ratio, etc. Mostly, these factors are affected each other during the gasification process. It is needed to study the gasification characteristics and the action mechanism of each factor. Firstly, a moving gasification bed is adopted to investigate the biomass gasification characteristics and mechanism in this paper. The pine sample is evenly distributed in a long tray and be sent into the furnace at a certain speed. At the same time, with a furnace temperature, linearly increasing from the entrance to the center of the furnace, the pine sample can be gradually heated up. Based on these, the experimental studies of pine gasification on different ER (air equivalent ratio), S/C (steam /carbon mole ratio) and the temperature T are carried through in this paper. The gas production rule and low calorific value of the syngas have been gotten with heating rate 25°C/min. At last, this paper gets the kinetic parameters of air gasification with different ER. Keywords: Continuous Gasification, Characteristics and mechanism, Pine, Experimental