• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.25 no.3
• /
• pp.419-426
• /
• 2021

A high-performance elliptic curve cryptography processor (HP-ECCP) was designed to support five field sizes of 192, 224, 256, 384 and 521 bits over GF(p) defined in NIST FIPS 186-2, and it provides eight modes of arithmetic operations including ECPSM, ECPA, ECPD, MA, MS, MM, MI and MD. In order to make the HP-ECCP resistant to side-channel attacks, a modified left-to-right binary algorithm was used, in which point addition and point doubling operations are uniformly performed regardless of the Hamming weight of private key used for ECPSM. In addition, Karatsuba-Ofman multiplication algorithm (KOMA), Lazy reduction and Nikhilam division algorithms were adopted for designing high-performance modular multiplier that is the core arithmetic block for elliptic curve point operations. The HP-ECCP synthesized using a 180-nm CMOS cell library occupied 620,846 gate equivalents with a clock frequency of 67 MHz, and it was evaluated that an ECPSM with a field size of 256 bits can be computed 2,200 times per second.

• Structural Engineering and Mechanics
• /
• v.88 no.4
• /
• pp.389-403
• /
• 2023

In order to explore the influence of tooth root cracks on the dynamic characteristics of multi-stage planetary gear transmission systems, a concentrated parameter method was used to construct a nonlinear dynamic model of the system with 30-DOF in bending and torsion, taking into account factors such as crack depth, length, angle, error, time-varying meshing stiffness (TVMS), and damping. In the model, the energy method was used to establish a TVMS model with cracks, and the influence of cracks on the TVMS of the system was studied. By using the Runge- Kutta method to calculate the differential equations of system dynamics, a series of system vibration diagrams containing cracks were obtained, and the influence of different crack parameters on the vibration of the system was analyzed. And vibration testing experiments were conducted on the system with planetary gear cracks. The results show that when the gear contains cracks, the TVMS of the system will decrease, and as the cracks intensify, the TVMS will decrease. When cracks appear on the II-stage planetary gear, the system will experience impact effects with intervals of rotation cycles of the II-stage planetary gear. There will be obvious sidebands near the meshing frequency doubling, and the vibration trajectory of the gear will also become disordered. These situations will become more and more obvious as the degree of cracks intensifies. Through experiments, the theoretical results are in good agreement with experimental results, verifying the correctness of the theoretical model. This provides a theoretical basis for fault diagnosis and reliability research of the system.

• Journal of The Korean Ophthalmological Society
• /
• v.58 no.3
• /
• pp.321-326
• /
• 2017

Purpose To identify the correspondence between the central sensitivity of several visual field (VF) tests and ganglion cell inner plexiform layer (GC-IPL) thickness in early glaucoma patients with parafoveal scotoma. Methods Fifty-seven eyes from 57 patients with glaucomatous optic neuropathy and parafoveal scotoma were analyzed using the standard automated perimetry (SAP) C10-2 test, the SAP C24-2 test, and the frequency doubling technology perimetry (FDT) C24-2 test. The correlation between the VF central sensitivity and the GC-IPL thickness from macular scans via optical coherence tomography was analyzed. Results The central sensitivity was $27.51{\pm}5.43dB$, $27.39{\pm}5.05dB$, and $22.09{\pm}5.08dB$ for SAP C24-2, SAP C10-2, and FDT C24-2, respectively. Mean GC-IPL thickness was $70.2{\pm}8.5{\mu}m$. Using regression analysis, the value of log $R^2$ between the logarithmic central sensitivity and GC-IPL thickness was 0.498, and the linear $R^2$ between the antilogarithmic central sensitivity and GC-IPL thickness in SAP C10-2 was 0.486, and both were statistically significant (p < 0.05). This relationship was stronger in early glaucoma patients compared to late glaucoma patients using SAP C10-2. Conclusions The structure-function relationship between GC-IPL thickness and central sensitivity was better with SAP C10-2, especially in early glaucoma patients, compared to other VF modalities.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.6
• /
• pp.1083-1091
• /
• 2017

This paper describes a design of cryptographic processor supporting 224-bit elliptic curves over prime field defined by NIST. Scalar point multiplication that is a core arithmetic function in elliptic curve cryptography(ECC) was implemented by adopting the modified Montgomery ladder algorithm. In order to eliminate division operations that have high computational complexity, projective coordinate was used to implement point addition and point doubling operations, which uses addition, subtraction, multiplication and squaring operations over GF(p). The final result of the scalar point multiplication is converted to affine coordinate and the inverse operation is implemented using Fermat's little theorem. The ECC processor was verified by FPGA implementation using Virtex5 device. The ECC processor synthesized using a 0.18 um CMOS cell library occupies 2.7-Kbit RAM and 27,739 gate equivalents (GEs), and the estimated maximum clock frequency is 71 MHz. One scalar point multiplication takes 1,326,985 clock cycles resulting in the computation time of 18.7 msec at the maximum clock frequency.

• Journal of Korean Ophthalmic Optics Society
• /
• v.4 no.2
• /
• pp.45-49
• /
• 1999

The second harmonic, wavelength is 397nm, of the continuous wave diode laser, whose maximum power is 35mW, was generated in $LiIO_3$ crystals in a ring enhancement cavity. 5mm- and 10mm-long crystals cut $43.21^{\circ}$ for optic axis were used in this experiment. Both surfaces of those were anti-reflection coated for 794nm. In case the crystal was inserted into the cavity, the condition of separation between two concave mirrors for the optimum mode matching was found. The conversion efficiency of second harmonic generation was increased by the resonant enhancement of pumping power in the ring enhancement cavity, and the frequency of diode laser was locked to that of the counter-propagation mode generated from the surface of crystal. When the pumping power was 28 mW, the infrared buildup factor was about 45 without the crystal, and 14 with the crystal due to the transmission loss of crystal. The maximum second harmonic powers of $1.5{\mu}W$ and $6.6{\mu}W$ were obtained, and corresponding conversion efficiencies were $(6.584{\pm}0.56){\times}10^{-3}$%, $2.6{\pm}0.21){\times}10%{-2}$% in 5mm- and 10mm-long $LiIO_3$, respectively.

• Applied Microscopy
• /
• v.34 no.1
• /
• pp.61-69
• /
• 2004

The microwave dielectric properties and microstructures of the Complex Perovskite (1-x)$(Li_{1/2}Sm_{1/2})TiO_3-x (Na_{1/2}Sm_{1/2})TiO_3$(LNST) system were investigated using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). LNST had not only the antiphase tilting of oxygen octahedron but also the inphase tilting of oxygen octahedron and the antiparallel shift of cations. Also, when $0.0{\leq}x{\leq}0.4$, LNST had the vacancy ordering of A-sites because of the evaporation of Li ions. From the observation of the microstructure, abnormal grain growth phenomena were observed over the whole range of x. The temperature coefficient of resonant frequency ($T_{cf}$) of the $({Li_{1/2}}^{+1}{Sm_{1/2}}^{+3})TiO_3$(LST) system has a large negative value ($-220ppm/^{\circ}C$) but the $({Na_{1/2}}^{+1}{Sm_{1/2}}^{+3})TiO_3$(NST) system which substituted $Na^{+1}$ has a large positive value ($+173ppm/^{\circ}C$). The dielectric properties of ${\varepsilon}_r=103,\;Q*f_{0}=3,700GHz$ and $T_{cf}=+50ppm/^{\circ}C$ at 4GHz were obtained when x =0.4.

• Korean Journal of Optics and Photonics
• /
• v.13 no.2
• /
• pp.140-145
• /
• 2002

We measured the absorption rate of a Nd:YVO$_4$crystal with a thickness of 1 mm and the output power characteristics of a cw Nd:YVO$_4$/KTP laser with respect to the change of wavelength and the polarizations of a tunable Ti:sapphire pump laser with a linewidth of 0.2 nm. In the case of S-polarization (E┴$\pi$) and P-polarization (E∥$\pi$) of a pump laser, the maximum absorption rate of the crystal was 82% at 809.4 nm and 98% at 808.8 nm, and slope efficiencies for the output power of the Nd:YVO$_4$laser (1064 nm) were 43% and 52%, respectively. The maximum Nd:YYO$_4$laser output power of 516 mW was obtained from the P-polarization pump laser of 1000 mW. As a result of an intracavity frequency-doubling, slope efficiency for the output power of the Nd:YVO$_4$/KTP green laker (532nm) was 23% and the maximum output power of 205 mW with the beam quality (M$^2$) of 1.42 was obtained from the P-polarization pump laser of 1000 mW.

• Progress in Medical Physics
• /
• v.18 no.2
• /
• pp.73-80
• /
• 2007

Fruitful findings have been produced from five out of sixty cells which were obtained from each 63 individual Aplisia caught at the Jeju coast. Spiking patterns of three out of five cells, such as relaxation oscillator, bursting within a short time of the inter-burst interval, chaotic bursting, period doubling sequences, bursting with long trains of action potentials separated by short silent periods, regular repeated beating or elliptic bursting, and silent states had been changed in order as the temperature was lowered to $10^{\circ}C\;from\;32^{\circ}C$. In the intervals of every about 40 minutes repeated ups and downs of temperature produced similar firing patterns at the allowable temperature ranges. The other two cells showed difference from these. The amplitudes of the action potentials of the two cells will not be highly decreased in 24 hours. Average spike frequencies, the inter-burst interval, peak to peak spike amplitude of action potentials, minimum potential values are compared and analyzed by using the computer programme. The spike frequencies according to temperature show the distribution of bell type, with maximal spike frequencies at intermediate temperatures and minimal ones at either end. The most common pattern consist of high spike frequency during failing and low one during rising temperatures.

• Journal of the Korean Applied Science and Technology
• /
• v.36 no.2
• /
• pp.394-406
• /
• 2019

The cellular senescence may be due to damage by the reactive oxygen species (ROS). This study has compared the antioxidant activity in the human cell lines of various origins, including 10S and 50S-derived normal skin fibroblasts, and 10S bone marrow, dental tissue and adipose-derived adult stem cells. After being exposed to $H_2O_2$, half inhibitory concentration ($IC_{50}$) values by cytotoxicity assay was significantly (P<0.05) lower in 50S-derived skin fibroblasts, than in 10S-derived skin fibroblasts and various adult stem cell lines. The cell population doubling time (PDT) and the cell frequency with high senescence associated-${\beta}$-galactose activity were remarkably increased in 50S-derived fibroblasts exposed to 50 ppm $H_2O_2$ for 7 days, than those of 10S-derived fibroblasts and various adult stem cell lines. Further, the expression level of antioxidant-related genes, glutathione peroxidase (GPX) and catalase (CAT), was investigated in 10S and 50S-derived skin fibroblasts, and 10S-derived various adult stem cells by reverse transcription polymerase chain reaction (RT-PCR). The expression level of GPX was higher in most of cell lines, compared to CAT, and a significantly (P<0.05) higher expression level of GPX was observed in 10S-derived skin fibroblasts and adult stem cell lines, compared to 50S-derived skin fibroblasts. We concluded that old-aged skin fibroblasts seemed to be less resistant against ROS than young-aged skin fibroblasts and adult stem cells.