When Ad Is Selfie: The Effect of Selfie on the Effectiveness of Ad Endorsers in Social Media

Selfie has proliferated in social media and capture the attentions from businesses. Although selfie has been leveraged into social commerce, little literature has understood and explained the effect of selfie. To solve this gap, this paper considers the effect of selfie on the effectiveness of ad endorsers and the moderating role of product type. We interpret selfie as a form of self-disclosure and study three types of ad endorsers: celebrities, experts and typical consumers. Given the nature of selfie and ad endorsers, we hypothesize that selfie enhance the effectiveness of celebrities and typical consumers, not experts. Besides, we also hypothesize that selfie improve the effectiveness of celebrities and typical consumer for hedonic product more than for utilitarian product, and experts is good for utilitarian product. Towards hypotheses in our paper, we plan to employ lab and field experimental method to test them. Potential theoretical and practical implications have been discussed

Design of Wideband Slot Array Antenna by Groove Gap Waveguide in Millimeter Waves

The newly introduced gap waveguide technology offers non-contact waveguide configurations so that the good electrical contact between different metallic layers can be avoided. Thereby, the gap waveguide structures are relatively simple to manufacture, especially at millimeter and sub-millimeter wave frequencies. This work systematically presents a high-efficiency corporate-fed slot array antenna based on groove gap waveguide in the millimeter waves. A cavity-backed slot sub-array is firstly designed in a groove gap waveguide cavity. The cavity is fed through a coupling hole from groove gap waveguide distribution network at the bottom layer. The sub-array is numerically optimized in an infinite array environment. Low side lobes are obtained in the both E- and H-planes by diagonal placement of the radiation slot rotating by 45 degrees. Furthermore, the radiation narrow slot pair is adopted so that the good cross polarization is achieved. The fabricated antenna depicts more than 25% bandwidth with input reflection coefficient better than -8 dB and the aperture efficiency higher than 60% with around 25 dBi realized gain between 70 and 90 GHz. The measured cross polarization level is below -27 dB, which satisfies the ETSI standard

Design of A Wideband Array Antenna Prototype with Gap Waveguide for W-Band Wireless Links

This paper presents a wideband 45o slot arrayantenna for W-Band wireless links. The proposed antennaprototype consists of 44 slot array, a wideband T-junctionbased on a groove gap waveguide and a vertical transitionfrom WR-10 to groove gap waveguide. The simulated resultsshow that the proposed prototype has an impedance bandwidthof 26.5% with input reflection coefficient better than-10 dB

Two Types of High Gain Slot Array Antennas based on Ridge Gap Waveguide in the D-Band

The recent introduced ridge gap waveguide shows huge strengths in array antennas in millimeter and sub-millimeter wave frequencies. Generally, gap waveguide supplies contactless characteristics in order to avoid the good electrical contact between the different metallic layers. Therefore, the gap waveguide structures are relatively simple to be fabricated in Ka-, V-, W-bands. As is well known, the conductor loss increases rapidly versus frequency in millimeter wave and submillimeter wave frequencies. Thereby, the increasing conductor loss above 100 GHz affects the antenna gain. In this work, we compare two types of antennas in the D-band. The full cooperate feed array antenna is wide band, avoiding the offset of main beam. However, the number of T-junction power dividers rapidly increases. Thereby, it is necessary to design a T-junction power divider with ultra-low reflection for a big array in the D-band so that the gain of the big array antenna enhances. On the other hand, a series feed antenna array is also a choice in the D-band. The series feed structure has advantages of less power dividers, easy design. Nevertheless, it is unable to avoid the long line effect, narrow bandwidth and main beam offset. The comparison between two structures has been done in the D-band in this work

Study of Dielectric Loss and Conductor Loss among Microstrip, covered Microstrip and inverted Microstrip Gap Waveguide utilizing variational Method in Millimeter Waves

In this paper,the classic variational method is applied for newly introduced inverted microstrip gapwaveguide.Then,the dielectric losses and the conductor losses among the microstrip, covered microstrip and inverted microstrip gap waveguide are analytically calculated based on the variational method in millimeter waves. According to our theory, the dielectric losses of microstrip and covered microstrip gap waveguide are at least 7 times higher than that of inverted microstrip gap waveguide. Therefore, inverted microstrip gap waveguide has huge advantage of low loss in millimeter waves

Analytical Solutions to Characteristic Impedance and Losses of Inverted Microstrip Gap Waveguide Based on Variational Method

This paper initially introduces analytical solutions to newly invented inverted microstrip gap waveguide (IMGW). By applying the classical variational method the characteristic impedance, dielectric loss, and conductor loss of the IMGW are obtained. The calculated characteristic impedance and losses of IMGWs with the present analytical method have been verified by commercial software CST. Furthermore, we have theoretically proved that the total loss of electromagnetic energy in the IMGW is much lower than that of covered microstrip line in millimeter waves (mmWs). Thereby, the IMGW has big advantages over covered microstrip lines for high-gain, high-efficiency array antennas in mmWs

Design of a 38 dBi Slot Array on Gap Waveguide at 140 GHz

In this paper, a cavity-backed full-corporate feed slot array antenna based on ridge gap waveguide at 140 GHz is presented. In order to fabricate the proposed slot array by computerized numerical control (CNC) milling technology, the length of metallic pins is selected as large as possible. Since the full-corporate feed networks are very dense, and only one row of metallic pins is required to isolate the coupling effect between any two neighbored distribution networks. In the work, height value of the bed nails are well selected so that the mutual coupling are below -20 dB. The simulated results show that the proposed array antenna has an input impedance bandwidth of 11% better than -10 dB. The bandwidth covers 135-150 GHz frequency band. The simulated gain is higher than 38 dBi over 135-150 GHz

Multiuser Beamforming for Partially-Connected Millimeter Wave Massive MIMO

Multiuser beamforming is considered for partially-connected millimeter wave massive MIMO systems. Based on perfect channel state information (CSI), a low-complexity hybrid beamforming scheme that decouples the analog beamformer and the digital beamformer is proposed to maximize the sum-rate. The analog beamformer design is modeled as a phase alignment problem to harvest the array gain. Given the analog beamformer, the digital beamformer is designed by solving a weighted minimum mean squared error problem. Then based on imperfect CSI, an analog-only beamformer design scheme is proposed, where the design problem aims at maximizing the desired signal power on the current user and minimizing the power on the other users to mitigate the multiuser interference. The original problem is then transformed into a series of independent beam nulling subproblems, where an efficient iterative algorithm using the majorization-minimization framework is proposed to solve the subproblems. Simulation results show that, under perfect CSI, the proposed scheme achieves almost the same sum-rate performance as the existing schemes but with lower computational complexity; and under imperfect CSI, the proposed analog-only beamforming design scheme can effectively mitigate the multiuser interference

Viability Discrimination of a Class of Control Systems on a Nonsmooth Region

The viability problem is an important field of study in control theory; the corresponding research has profound significance in both theory and practice. In this paper, we consider the viability for both an affine nonlinear hybrid system and a hybrid differential inclusion on a region with subdifferentiable boundary. Based on the nonsmooth analysis theory, we obtain a method to verify the viability condition at a point, when the boundary function of the region is subdifferentiable and its subdifferential is convex hull of many finite points