Electrically controllable spin filtering in zigzag phosphorene nanoribbon based normal–antiferromagnet–normal junctions

We investigated the electric controllable spin-filtering effect in a zigzag phosphorene nanoribbon(ZPNR) based normal–antiferromagnet–normal junction. Two ferromagnets are closely coupled to the edges of the nanoribbon and form the edge-to-edge antiferromagnetism. Under an in-plane electric field, the two degenerate edge bands of the edge-to-edge antiferromagnet split into four spin-polarized sub-bands and a 100% spin-polarized current can be easily induced with the maximal conductance 2e~2/h. The spin polarization changes with the strength of the electric field and the exchange field,and changes sign at opposite electric fields. The spin-polarized current switches from one edge to the other by reversing the direction of the electric field. The edge current can also be controlled spatially by changing the electric potential of the scattering region. The manipulation of edge current is useful in spin-transfer-torque magnetic random-access memory and provides a practical way to develop controllable spintronic devices.

Analysis of Mechanically Tunable Frequency Selective Surfaces

The frequency selective surface (FSS) has been widely applied by means of its spatial frequency-filter characteristic, but it is always designed and used as a device with fixed frequency response. In order to tune the resonant frequency and switch the frequency channel, a scheme of mechanically tunable FSS is theoretically analyzed by using the method of Floquet's vector modes expansion and fields matching. A double-layer tunable FSS with dipole element can perform a dynamic range of resonant frequency covering whole X-band.

Enhancement of filtration efficiency by electrical charges on nebulized particles

There have been few investigations of effects of electrical charge, carried by lab-generated particles, on filtration efficiency testing. Here, we measured the elementary charge on particles and the fraction of particles carrying that charge with a combined electrometer, differential mobility analyzer, and scanning mobility particle sizer. A typical solid NaCI aerosol and liquid diethylhexyl sebacate （DEHS） aerosol were generated with Collison and Laskin nebulizers, respectively. Our experimental results showed that NaCI aerosols carried more charge after aerosol generation. The average net elementary charge per particle was approximately 0.07. The NaCI aerosol was overall positively charged but contained a mixture of neutral and charged particles. Individual particles could carry at most four elementary charges. According to constant theorem, we speculated that original NaC1 aerosol contained 17% neutral, 45% positive-, and 38% negative-charged particles in the diameter range from 30 to 300nm. A Kr-85 neutralizer was used to decrease the charge on the NaCI particles. Our results indicated that the DEHS aerosol was electrically neutral. The effects of electric charge on particle collection by electret and electroneutral high efficiency particulate air （HEPA） filters were analyzed. Theoretical calculations suggested that charges on original NaCI aerosol particles enhanced the filtration efficiency of HEPA filters,

Closely packed dense frequency selective surface

In order to realize wideband filtering properties of frequency selective surface （FSS）, FSS of closely packed elements is presented. The Y loop elements are chosen as the graphics elements. Based on the spectral domain method, the frequency response is analyzed for different incident angles and polarizations. The result of the numerical analysis shows that the dense FSS has wide passband with better independence of angle and polarization.

Research on asymmetric “Jerusalem” unit

An asymmetric Jerusalem unit and the frequency selective surface （FSS） structure composed of such units are designed. The transmittance of the designed FSS structure is calculated by mode-matching method and compared with the test results. The comparison results show that the FSS center frequency of the asymmetric structure unit drifts little with the variation of the incident angles of the electromagnetic waves and keeps relatively stable. The research offers a new choice for the application of FSS under the large scanning angle of electromagnetic waves.

High channel-count comb filter based on multi-concatenated sampled chirped fiber Bragg gratings

A high channel-count comb filter based on multi-concatenated sampled chirped fiber Bragg gratings （MC- SCFBGs） is proposed and optimally designed by using several chirped gratings with different fundamental grating periods, instead of non-grating sections of SCFBGs. The numerical simulations of the reflection spectra show that the channel spacing and the channel bandwidth in MC-SCFBGs are smaller than those in multi-concatenated chirped fiber Bragg gratings （MC-CFBGs） and that the spectral bandwidth of MC-SCFBGs can be greatly broadened by increasing the cascade number of the grating sections in each samDling Deriod.