Multi-hexaferrites (Sr_3-xCa_xCo₂Fe₂₄O₄₁, x = 0, 0.1, 0.2, 0.3, 0.4) with more than two types of hexaferrite phases were synthesized by solid-state reactions and substitution of Sr by Ca in the stoichiometric Z-type Sr₃Co₂ hexaferrite composition. Multi-hexaferrites consisting of Z + U +W, X + U +W, and X +W phases were formed for the samples with x = 0, x = 0.1, and x ≥ 0.2, respectively, upon first and second calcinations at 1160 and 1210 ℃. The saturation magnetization increased largely with Ca-doping (x ≥ 0.1). The complex permeability spectra were shifted to higher frequency and the imaginary permeability peak became broader by Ca doping. In the RL maps plotted as functions of sample thickness (d) and frequency (f), the strong EM absorbing area moved to higher f and lower d direction with increasing of x. For the Ca-doped samples (x ≥ 0.1), the minimum reflection loss (RL < -30 dB) corresponding to the maximum microwave absorption was obtained at f = 10 GHz vicinity and d = ~2 mm, while the undoped sample exhibited the minimum RL (-42 dB) at f = 4.6 GHz and d = 4.6 mm. The highest EM wave absorption performance of RL = -56.5 dB could be achieved at the sample of x = 0.3 with d = 2.2 m m and f = 11.4 GHz. For the x = 0.2 samples, RL < -10 dB (EM energy absorption above 90%) is satisfied in the full X-band frequency range (8~12 GHz) with d = 2.3 mm. The broad-band EM absorption properties could be achieved owing to the overlaps of the hard-soft magnetic properties of the multi-hexaferrites.

We analyzed the magnetic field dependence of 0^th, 1^st and 2^nd order harmonic signals (V_0f0, V_1f0 and V_2f0) measured in planner Hall resistance (PHR) sensor. The magnetic field dependence of V_1f0 showed the typical PHR signal properties with high sensitivity and linearity near H = 0. While, the magnetic field dependence of and V_2f0 showed same as the derivative of the magnetic field dependence of V_1f0, and were very sensitively response to the magnetic film on PHR sensor.

We used coil sensor and PHR sensor in order to measure the amplitude and phase of eddy current signals induced by flaws. The amplitude and phase of eddy current signals were propositional to depth of flaws in both sensor. The phase of eddy current signals measured by PHR sensor were more larger than that measured by coil sensor. The benefits of tiny PHR sensor compared with coil sensor were high spatial resolution as well as very high flaw detection capability at low frequency.

In this paper, the performance of the proposed closed-loop degaussing technique is analyzed through testing a mockup replicating a magnetic field condition of a ship due to the variation of on-board equipment’s or hull’s magnetization. In order to change a magnetic field condition of the mockup, a certain electric current is applied to triaxial coils installed in a nonmagnetic laboratory. Before and after the artificial field condition, degaussing current values are respectively derived from closed-loop degaussing algorithm and then applied to individual degaussing coils. The effectiveness of the proposed degaussing technique is verified by comparison of the magnitude of field signals generated on a certain depth of water.

Imbalance of blood circulation caused by aggregation, rouleaux and morphological transform of red blood cell (RBC) influenced to cardiovascular diseases such as thrombosis, peripheral stenosis, and arteriosclerosis. This study intends to evaluate the effect of the pulsed magnetic field (PMF) on the aggregation and deformability of RBC. In hematocrit (HCT) 45% bloods diluted with phosphate buffered saline (PBS) and plasma, ESR rates were slowed by 1% and 6% after PMF stimulus of 2700 G, respectively. In addition, RBCs’ sedimentation rate after 12 hrs decreased to 25% at 2700 G, 28% at 1000 G, 32% at 400 G, compared to 34% at non-PMF group. After tBHP treatment in order to observe the RBC aggregation due to hemoglobin oxidation, the RBCs sedimentation proceeded rapidly, but progressed slowly after PMF stimulus. In RBC deformability experiment using filter having a size of 5 μm smaller than the volume of RBC, the number of filtered RBCs increased by 2% at 400 G, 16% at 1000 G and 29% at 2700 G, compare with non-PMF group. For oxidative RBCs group, it also increased by more than 34% after PMF stimulus. Improvement of RBCs’ aggregation after PMF stimulus could be interpreted as the instantaneous rapid flux change of PMF affecting the zeta potential of RBCs. Also it is believed that PMF also affects the Ca²⁺ ion pump which affects the hardening of RBCs’ membrane, thereby increasing the RBCs’ deformability. Therefore, the PMF stimulus could be used as a non-invasive treatment method for blood circulation disorder.