EULER CHARACTERISTIC OF TANGO BUNDLES

We are interested in a vector bundle constructed by Tango (1976). The Tango bundle is an indecomposable vector bundle of rank n-1 on the complex projective space P^n. In particular, we show that the Euler characteristic of the Tango bundle on P^n is equal to 2n-1

Characterization of pig farms in Hung Yen, Hai Duong and Bac Ninh provinces

peer reviewedIn order to characterization of pig farms in the Red River Delta, a study was conducted on 90 pig farms in Hung Yen, Hai Duong and Bac Ninh provinces from June to December 2006. Results show that most of the pig farms had been built for five years with a small size (0.5 hectare per farm). The invested capital was about 300-400 millions VND per farm. Four main sow groups used in the farms included crossbred exotic sows (51.1%), crossbred sow between local and exotic breeds (14.4%), purebred Landrace and Yorkshire breeds (15.6 and 18.9%, respectively). The boars were various (Duroc 30%, Yorkshire 21%, Landrace 13%, PiÐtrain × Duroc 36% and others). The pigs farms were faced with several difficulties such as limited land, lack of invested capital, uncontrolled quality of breeding pigs, high costs of feed, poor hygiene condition and diseases

Average symbol error rate analysis of reconfigurable intelligent surfaces based free-space optical link over Weibull distribution channels

Optical wireless communication (OWC) enables wireless connectivity using ultraviolet bands, infrared or visible. With its advantages features as high bandwidth, low cost, and operation in an unregulated spectrum. Free-space optical (FSO) communication systems are near terrestrial as a communication link between transceivers, the link is line-of-sight and successfully transmitted optical signals. Nevertheless, the optical signals transmissions over the FSO channels bring challenges to the system. To overcome the challenges posed by the FSO channels, the most common technique is to use relay stations, the most recent is the reconfigurable intelligent surfaces (RISs) technique. This study introduces a Weibull distribution model for a free-space optical communication link with RISs assisted, the parameter used to evaluate the performance of the system is the average symbol error rate (ASER). The RISs effect is examined by considering the influence of the transmitter beam waist radius, shape parameter, aperture radius, scale parameter, and signal-to-noise ratio on the ASER

Assessing the Potential of Climate Smart Agriculture in Large Rice Field Models in Vietnam

This study assesses the economic, social, and environmental impacts of Large Field Models (LFMs) and their potential for promoting Climate-Smart Agriculture (CSA). In Vietnam, the government introduced the Large Field Model (LFM), a type of production organization, in which enterprises or cooperatives establish a cooperative relationship with farmers to apply a unification production procedure by providing production inputs (including material and technical support) and/or buying outputs from producers. These LFMs can be classified under three different forms based on the extent of those linkages: (1) farmers contribute land and/or labour to farmer cooperatives; (2) farmers sign contracts with cooperatives or enterprises and receive inputs; and (3) farmers lease out/sell their land to cooperatives or enterprises. Although the key objectives of constructing LFMs come from requirements in improving rice quality and rice production efficiency, these models also have potential for applying CSA to achieve three CSA pillars: productivity, resilience and mitigation. Productivity: the LFMs ensure integration between enterprises and farmers, wherein rice production is promoted, given that the output is sold at a more stable price. Therefore, farmers confidently manage their business to increase productivity. In addition, higher output price and lower production cost is observed from LFMs’ production. Better output price comes from the commitments of enterprises and higher rice quality produced from LFMs. The reduction in production costs is also achieved by taking advantage of economy of scale to apply modern agricultural machinery (such as tractors) and thus reduce labour costs. Resilience: this CSA pillar is created indirectly from LFMs. In general, as farmers use LFMs, they have a better chance to access certified seeds and follow the production procedures of enterprises under the direct support from technicians, and they are less likely to be exposed to disease epidemics than non-participant farmers. In addition, farmers who sign contracts with enterprises/cooperatives or work in LFMs tend to share their knowledge and discuss weather issues with technicians before deciding when to sow or harvest to reduce climate risks. Mitigation: the LFM production contributes to reduced GHG emissions. LFMs created a foundation to apply advanced cultivation methods and to follow strictly modern techniques such as: One Must Five Reductions (1M5Rs), Three Reductions Three Gain (3R3G), 4 Alternate Wetting and Drying (AWD), System of Rice Intensification (SRI), and Deep Fertilizer Placement (DPF). The synchronized irrigation timing or flattened surface field of LFMs also contributes more efficient water use. Moreover, this model changes farmer behaviours toward more efficient and environmentally friendly paddy straw treatment to mitigate environmental impacts. In sum, there are potentials for promoting CSA application in LFMs. The integration developed through LFMs will produce friendly and mutually beneficial networks of farmers to share knowledge and modern techniques. This also encourages farmers to improve cultivating skills and output quality to sustain their contracts with better enterprises in the long run. In addition, the pressure from climate risks will push farmers to act collectively to adapt and mitigate environmental impacts. These potentials should be accompanied by the strong support from the government through its response to climate changes in the Nationally Determined Contribution (NDCs). However, there are still many constraints for expanding CSA application into LFMs. First, traditional cultivation and small landholding habits make it difficult for enterprises to accumulate land to form LFMs. Even when farmers agree to contribute their land to cooperatives, this model is still struggling to establish the appropriate benefit-sharing method in order to keep it working smoothly in the long run, especially due to land price fluctuations. Second, there are infrastructure-related issues. Some types of CSA practices require infrastructure support, for example irrigation systems for applying Alternate Wetting and Drying (AWD). Finally, there is a need for a legal mechanism to bind contracts between enterprises and farmers, especially under high price volatility. Vietnam’s policy system to enhance CSA application and expand LFMs is still characterized by limitations related to effectiveness, validation and public-private participation. This requires a change to attract the participation of local government, enterprises, and farmers. For example, experience from other countries shows that in the case of small scale production, legal measures would not be feasible because of high transaction costs. Therefore, using community value to bind farmers to contracts is the most feasible measure that has been proven. In addition, support for developing agricultural insurance and infrastructure investment is important. However, before expanding CSA application into LFMs, detailed studies of LFMs in each region are required because each model might be more efficient for one specific region with a specific crop

AN UPDATED CHECKLIST AND COMMENTS FOR SECTION PIQUETIA (CAMELLIA, THEACEAE)

New Camellia species in section Piquetia have recently been discovered. It is necessary to enumerate the number of species and update the specific characteristics of this section. Based on the study of more than 30 pieces of literature and a large number of specimens, a total of 15 species belonging to section Piquetia, including two new species, are identified. A taxonomic key to all species is provided, and typical characteristics of the section are also discussed. Information on the distribution, ecology, and conservation status of each species, as well as notes on the differences between closely related species, is also provided.

. In vitro propagation of the new orchid Dendrobium trankimianum T. Yukawa

Dendrobium trankimianum T. Yukawa is a beautiful, endemic orchid of Vietnam, a new species with a first - published description in 2004. It is very rare and expected to be added to the IUCN Red List status - CR. In vitro studies of orchid D. trankimianum T. Yukawa were conducted in order to conserve and increase the genetic pool of this precious wild orchid species. The results showed that full-strength MS medium supplemented with 2.0 mg/L BA and 0.5 mg/L NAA (10.24 PLBs/explant; 90.11% explants formed PLBs) or full-strength MS medium supplemented with 1.5 mg/L TDZ and 0.5 mg/L NAA (14.11 PLBs/explant; 92.06% explants formed PLBs) were the most suitable for protocorm formation. For subculture, suitable growth of shoots were obtained on full-strength MS medium supplemented 1.5 mg/L BA (22.35 shoots/explant; shoots length of 1.96 cm) and full-strength MS medium supplemented with 60 g ripe banana per liter (25.11 shoots/explant; shoots length of 2.12 cm). The shoots in vitro were transferred to half-strength MS supplemented with different concentrations of IAA, IBA and NAA to investigate root formation. The best rooting occurred at 0,5 mg/L NAA (7.91 roots/shoot; root length of 4.01 cm; 98.51% root formation). The plantlets with uniform growth were planted on different substrate: Eco clean soil, Coconut fiber, Fern fiber, 50% Rice husk in combination with 50% Eco clean soil for research the most suitable substrate. After 60 days of transplantion and acclimatization, the result showed that Fern fiber was suitable substrate for plantlet growth in a nursery garden (8.0 roots/ explant; root length of 5.5 cm; survival rate of 93.29%)

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

Deep Learning-Based Signal Detection for Dual-Mode Index Modulation 3D-OFDM

In this paper, we propose a deep learning-based signal detector called DuaIM-3DNet for dual-mode index modulation-based three-dimensional (3D) orthogonal frequency division multiplexing (DM-IM-3D-OFDM). Herein, DM-IM-3D- OFDM is a subcarrier index modulation scheme which conveys data bits via both dual-mode 3D constellation symbols and indices of active subcarriers. Thus, this scheme obtains better error performance than the existing IM schemes when using the conventional maximum likelihood (ML) detector, which, however, suffers from high computational complexity, especially when the system parameters increase. In order to address this fundamental issue, we propose the usage of a deep neural network (DNN) at the receiver to jointly and reliably detect both symbols and index bits of DM-IM-3D-OFDM under Rayleigh fading channels in a data-driven manner. Simulation results demonstrate that our proposed DNN detector achieves near-optimal performance at significantly lower runtime complexity compared to the ML detector

Secondary Network Throughput Optimization of NOMA Cognitive Radio Networks Under Power and Secure Constraints

Recently, the combination of cognitive radio networks with the nonorthogonal multiple access (NOMA) approach has emerged as a viable option for not only improving spectrum usage but also supporting large numbers of wireless communication connections. However, cognitive NOMA networks are unstable and vulnerable because multiple devices operate on the same frequency band. To overcome this drawback, many techniques have been proposed, such as optimal power allocation and interference cancellation. In this paper, we consider an approach by which the secondary transmitter (STx) is able to find the best licensed channel to send its confidential message to the secondary receivers (SRxs) by using the NOMA technique. To combat eavesdroppers and achieve reasonable performance, a power allocation policy that satisfies both the outage probability (OP) constraint of primary users and the security constraint of secondary users is optimized. The closed-form formulas for the OP at the primary base station and the leakage probability for the eavesdropper are obtained with imperfect channel state information. Furthermore, the throughput of the secondary network is analyzed to evaluate the system performance. Based on that, two algorithms (i.e., the continuous genetic algorithm (CGA) for CR NOMA (CGA-CRN) and particle swarm optimization (PSO) for CR NOMA (PSO-CRN)), are applied to optimize the throughput of the secondary network. These optimization algorithms guarantee not only the performance of the primary users but also the security constraints of the secondary users. Finally, simulations are presented to validate our research results and provide insights into how various factors affect system performance

Secondary Network Throughput Optimization of NOMA Cognitive Radio Networks Under Power and Secure Constraints

Recently, the combination of cognitive radio networks with the nonorthogonal multiple access (NOMA) approach has emerged as a viable option for not only improving spectrum usage but also supporting large numbers of wireless communication connections. However, cognitive NOMA networks are unstable and vulnerable because multiple devices operate on the same frequency band. To overcome this drawback, many techniques have been proposed, such as optimal power allocation and interference cancellation. In this paper, we consider an approach by which the secondary transmitter (STx) is able to find the best licensed channel to send its confidential message to the secondary receivers (SRxs) by using the NOMA technique. To combat eavesdroppers and achieve reasonable performance, a power allocation policy that satisfies both the outage probability (OP) constraint of primary users and the security constraint of secondary users is optimized. The closed-form formulas for the OP at the primary base station and the leakage probability for the eavesdropper are obtained with imperfect channel state information. Furthermore, the throughput of the secondary network is analyzed to evaluate the system performance. Based on that, two algorithms (i.e., the continuous genetic algorithm (CGA) for CR NOMA (CGA-CRN) and particle swarm optimization (PSO) for CR NOMA (PSO-CRN)), are applied to optimize the throughput of the secondary network. These optimization algorithms guarantee not only the performance of the primary users but also the security constraints of the secondary users. Finally, simulations are presented to validate our research results and provide insights into how various factors affect system performance