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Purpose The purpose of our study is to examine the direct and mediating effects of attention-deficit hyperactivity disorder (ADHD) symptoms and urgency, lack of premeditation, lack of perseverance and sensation seeking (UPPS) impulsivity traits on entrepreneurial self-efficacy and entrepreneurial intention as well as to test the moderation impact of ADHD symptoms in the link between entrepreneurial self-efficacy and start-up intention.Design/methodology/approach The stratified random sampling was approached to recruit the data from 2,566 university students in Vietnam. Cronbach’s alpha and confirmatory factor analysis were used to test the reliability and validity of scales. Then, Pearson correlation analysis was utilized to test direct effects, while PROCESS macro was approached to test moderation and mediation impacts.Findings The study found evidence that ADHD symptoms, sensation seeking, lack of premeditation and lack of perseverance are significantly and directly conducive to the formation of entrepreneurial intention. Yet, ADHD symptoms might weaken the link between entrepreneurial self-efficacy and entrepreneurial intention. Entrepreneurial self-efficacy was also found to partially mediate the link between sensation seeking, lack of premeditation, and lack of perseverance and intention to become an entrepreneur.Practical implications The findings provide constructive recommendations for policymakers and educators to nurture and foster university students’ entrepreneurial activities as well as to restrain the negative effects of ADHD symptoms on youths.Social implicationsUnderstanding the impacts of psychiatric symptoms, such as ADHD and UPPS impulsivity, on entrepreneurial activities provide useful insights to individuals with ADHD symptoms, the community and the society to restrain the detrimental impacts of psychological disorder symptoms and consider entrepreneurship as a career choice.Originality/value The study is expected to have a significant contribution to psychological entrepreneurship literature by broadening our horizons of the links between psychiatric symptoms and entrepreneurial intentions. Especially, this study reveals that ADHD symptoms and UPPS impulsive traits are significantly correlated with intention to become entrepreneurs and the link between entrepreneurial self-efficacy and entrepreneurial intention become weaker when the degree of ADHD symptoms is high.

In this paper, we study a free boundary problem of two competing species in the left-shifting environment. This model may be used to describe the interaction of the spreading phenomena of two competing species over a one dimensional habitat influenced by an external effect such as the effect of global warming. Here, we assume that only the habitat of inferior competitor is eroded away by the left moving boundary at constant speed c and we consider the how its spreading influences to the spreading of the superior competitor. We prove, as $c_{2}^{\ast }

Caching and resource sharing (CRS) optimization is a promising joint technique to stimulate video streaming applications and services (VASs) in 5G networks. Solving the CRS optimization problem by using exhaustive algorithms (EAs) can provide exact optimal results, but it is not good enough to apply to a larger scale of 5G networks, i.e., 5G ultra-dense networks (UDNs) due to high memory and time complexity. In this paper, we study genetic algorithms (GAs) to solve the CRS optimization problem in 5G UDNs at reasonable memory and time complexity for approximated or exact optimal results. To do so, the GAs solution which often finds optimal real values under simple constraints in the form of lower and upper bounds is modified for finding optimal binary values under more complicated constraints by applying penalty method. Simulation results are shown to validate that the GAs are able to solve the CRS optimization problem not only for the optimal results at high accuracy (up to 99.99%) and low complexity compared to the EAs but also for more insightful analyses of system performance in 5G UDNs.

In recent years, intelligent transport system (ITS) applications with unmanned ground vehicles (UGV) have increased dramatically to improve the safety, efficiency, and unique services in low- to medium-range communication deployment. Orthogonal frequency division multiplexing (OFDM) is adopted as a modulation scheme for this communication system to combat fading. Unfortunately, because of possible high UGV speed, the orthogonality between subcarriers in OFDM signals is prone to intercarrier interference (ICI) caused by the Doppler spread. This paper discusses ICI suppression analysis using Universal Software Radio Peripheral (USRP) N210 under several Harbor transmission scenarios. Such communication links may contain line of sight (LoS) components in transmission. The channel is thus modeled as the well-known fast time varying path loss model. Furthermore, this paper derives the signal to interference ratio (SIR) and evaluates this parameter for several types of fading and Doppler spread shapes in UGV channels. Additionally, the paper presents a practical method for calculating the spectral efficiency of OFDM systems, with an example for actual implementation in UGV systems. Eventually, the testbed results indicate that the SIR will decrease if the maximum Doppler spread expands. In the Rician channel, it can be seen that the SIR depends on the maximum Doppler speed, the angle of arrival (AoA), and even the Rician element of the LoS component. Published version

In wireless multimedia sensor networks (WMSNs), multimedia contents from remote areas are captured by camera sensors (CSs) and sent to data center via cluster heads (CHs) and base stations (BSs) for the purpose of monitoring. The problem in WMSNs is that enabling multimedia streaming, e.g., video streaming, demands high quality and consumes considerable bandwidth and energy resources, meanwhile, the CSs, CHs, and wireless channels are energy- and bandwidth-constrained and diverse lossy. In this paper, we propose a joint time switching and rate allocation optimization scheme for WMSNs to minimize energy consumed by capturing, packetizing, and transmitting the video contents, while conserving bandwidth and guaranteeing high quality. In particular, firstly, a time switching optimization (SOP) problem is formulated and solved for optimal capture durations of each CS, so as to minimize the capture energy consumption. Secondly, to minimize energy consumed by packetizing and transmitting, we formulate a rate allocation optimization (ROP) problem and solve it for optimal rates allocated to each video for packetizing and transmitting under bandwidth resource and quality constraints. Simulation results show that our proposed SOP and ROP schemes can significantly enhance the performance of WMSNs in terms of minimum energy consumption, bandwidth efficiency, and high quality.

Electromechanical wave imaging (EWI) is a novel ultrasound-based imaging modality for mapping of the electromechanical wave (EW), i.e. the transient deformations occurring in immediate response to the electrical activation. The correlation between the EW and the electrical activation has been established in prior studies. However, the methods used previously to map the EW required the reconstruction of images over multiple cardiac cycles, precluding the application of EWI for non-periodic arrhythmias such as fibrillation. In this study, new imaging sequences are developed and applied based on flash- and wide-beam emissions to image the entire heart at very high frame rates (2000 fps) during free breathing in a single heartbeat. The methods are first validated by imaging the heart of an open-chest canine while simultaneously mapping the electrical activation using a 64-electrode basket catheter. Feasibility is then assessed by imaging the atria and ventricles of closed-chest, conscious canines during sinus rhythm and during right-ventricular pacing following atrio-ventricular dissociation, i.e., during a non-periodic rhythm. The EW was validated against electrode measurements in the open-chest case, and followed the expected electrical propagation pattern in the closed-chest setting. These results indicate that EWI can be used for the characterization of non-periodic arrhythmias in conditions similar to the clinical setting, in a single heartbeat, and during free breathing.

In emergency scenarios, e.g., natural disasters, the infrastructure of telecommunication system is partially or even completely disrupted. While the bandwidth and energy resources of system are limited, the maltimedia communication demand of myriad usen may reach the peak of data traffic. This in tum makes the system more challenging to serve the users high quality of maltimedia streaming with con.served resources. In this paper, we address this challenge by proposing an efficiency rate allocation optimization scheme for video streaming applications (VSAs) over large-scale heterogeneous emergency wireless mesh networks (WMNs). In particalar, on the one hand, WMNs provide easy implementation, quick recovery, broadband wirele11 applications, and low cost that can meet the significant requirements of emergency communication 1ystems. On the other hand, we formulate a rate aDocation optimization problem in the context that the whole system of VSAs over WMNs is categorized into different disaster areas characterized by diverse demand/behavior of usen and condition/resource of networks. SoMng this optimization problem, each Tideo is thus adaptively encoded at different optimal rate corresponding to each area 10 as to maximi~ the quality of VSAs, while conserving the bandwidth and energy resources. Simulation resalts are shown to demonstrate the benefits of proposed optimization scheme.

The proliferation problem of video streaming applications and mobile devices has prompted wireless network operators to put more efforts into improving quality of experience (QoE) while saving resources that are needed for high transmission rate and large size of video streaming. To deal with this problem, we propose an energy-aware rate and description allocation optimization method for video streaming in cellular network assisted device-to-device (D2D) communications. In particular, we allocate the optimal bit rate to each layer of video segments and packetize the segments into multiple descriptions with embedded forward error correction (FEC) for realtime streaming without retransmission. Simultaneously, the optimal number of descriptions is allocated to each D2D helper for transmission. The two allocation processes are done according to the access rate of segments, channel state information (CSI) of D2D requester, and remaining energy of helpers, to gain the highest optimization performance. Simulation results demonstrate that our proposed method (named OPT) significantly enhances the performance of video streaming in terms of high QoE and energy saving. 2015 IEEE. Scopus 2-s2.0-84953774897

The performance of a cognitive radio (CR) system depends on how to optimally allocate available resources (e.g., bandwidth, subcarrier and power) of a free frequency band without causing any interference to the primary user (PU). We consider a secondary usage of spectrum scenario with the coexistence of primary and secondary users. For such a system, we study the problem of optimizing subcarrier and power allocation with the objective of maximizing sum capacity of CR users such that the received interference at primary users remain below a threshold level as well as mutual interferences between secondary users are guaranteed to be below a satisfied threshold. The CR coordinator needs to determine the position and power which are assigned to each CR user while considering the interference threshold between CR users and from PU to CR users. The proposed scenario is valid in Broadcast, Unicast and Multicast transmission. The effects of adjacent the number of subcarriers for each CR user, which is to reduce mutual interference between CR users and interference between CR and PU, on the proposed scenario have been presented. Numerical studies are performed to compare the performance of CR system with and without considering of mutual interference.

Video on-demand service (VoDs) over broadband wireless Internet have become well-known and increasingly attractive to users. The huge number of users and the limited resources of media servers and wireless channels make VoDs more challenging to serve the users high quality of video streaming applications. In this paper, we introduce and analyze an optimization problem used for replication strategy in VoDs over broadband wireless Internet. The solution of this problem enables VoDs to distribute “hot” videos into all peers so as to: 1) minimize bandwidth consumption at the media servers and 2) minimize wasted bandwidth and utilize storage capacity at the peers. A particular example is shown to demonstrate the benefit of the proposed optimization solution.

In this paper, we focus on the physical layer secrecy performance analysis of Ultra Wideband system consisting of a multi-antenna transmitter using transmit antenna selection and single antenna receiver, in the presence of a single antenna passive eavesdropper over Rayleigh fading channel. Specifically, the exact closed-form expressions of probability of existence of secrecy capacity and the secrecy outage probability are derived by using statistical characteristics of the signal-to-noise ratio. The analytical results are verified by Monte-Carlo simulations.

The basic structure of the Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) Ultra-Wide Band (UWB) System is discussed in this paper. The fixed-point simulation platform using the WiMedia Alliance proposed by ECMA 368 standards has been implemented. An extension of the physical layer using the Alamouti method to a Multiple-Input Multiple-Output (MIMO) system is also presented. Based on the theoretical Dual Carrier Modulation (DCM) supported by Media Alliance, we propose a scheme of the DCM-Modulation and DCM-Demodulation with Soft-decoding for a MB-OFDM MIMO system. The system performance is analyzed using the Saleh-Valenzuela channel model in terms of the bits error rate and the transmission range for indoor environments.

Recently, ultra-wideband (UWB) is one of the most attractive technologies in communications. UWB communication systems are designed to intent to low power, low cost, and low complexity devices. However, costly high-speed analog-to-digital converters (ADCs) is required to convert RF/IF signals to digital form for subsequent baseband processing in UWB system. By exploiting sparse property of UWB signal, using compressive sensing (CS) to reduce the sampling rate is a perspective approach. In this paper, we propose a UWB communications system using compressive sensing combined with time-hopping (TH) pulse position modulation (PPM) and pulse amplitude modulation (PAM), called CS-TH-UWB. This system is designed aims to reduce the sampling rate of the origin UWB system. CS technique possesses capability to implement under Nyquist sampling rate at transmitter side. At the receiver side, the under Nyquist rate samples are reconstructed with an acceptable loss. The simulation of this system is carried out to evaluate the BER of CS-TH-UWB. The results show that at low compression ratio of sampling rate, the different in BER performance is negligible. The higher compression ratio is the more degradation of BER performance.