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Objectives: The aim of this study was to evaluate the level of hematuria and the presence of clots during retrograde intrarenal surgery (RIRS) and miniaturized percutaneous nephrolithotomy (mPCNL) to predict surgical outcomes. Materials and Methods: The data of patients who underwent RIRS and mPCNL were analyzed separately. A hematuria grading (HG) system was classified into five grades based on the presence of blood clots and any visible stones according to the irrigation settings. Inter-observer reliability of the grading system was assessed using intra-class correlation and Spearman’s rho. Results: The HG system showed high agreement among examiners, with high intra-class reliability and a strong correlation between RIRS and mPCNL groups. The stone density of the Houns-field unit was the most important factor in determining the hematuria across the development and validation groups of RIRS and mPCNL patients. Multivariate logistic regression analysis showed that the HG system was a significant predictor for remnant stones in the PCNL group and the probability of acute pyelonephritis or sepsis in the RIRS group. The high hematuria group showed lower basketing difficulty with the basket with a blue marker instrument than with others. Conclusions: The new HG system shows excellent inter-observer reliability and a correlation with a gradual increase in stone density and surgical difficulty.

Frequency-modulated continuous wave (FMCW) system was implemented using dual interferometers with two different optical delay lengths. This system can overcome the limitation of the distance measurement range due to the coherence length of the light source.

In this research, we have proposed a dual-wavelength comb-swept laser and optical Vernier sampling technique for multi-layer measurement. With the proposed measurement system, we can measure multi-layer targets without distance aliasing.

We have proposed a multimode-fiber identical weak FBG array interrogation based on resonance frequency mapping (RFM). We fabricated five identical weak FBGs in the graded-index fused silica fiber with intervals of approximately 1 m and then multiplexed all of them based on RFM successfully.

This paper reports the real-time linear-in-distance sampling for a resonance frequency mapping system based on an identical weak fiber Bragg grating (FBG) array. Based on a function of an external clock for the sampling timing of uniform distance spacing, 100 identical weak FBGs could be interrogatedexamined with a high linearity of 0.9996 (R2).

We present a novel design for a wavelength-switchable nanosecond-pulsed erbium-doped fiber laser that simultaneously achieves a repetition rate of the order of hundreds of kilohertz as well as pulse energies in the hundred-nanojoule range to fulfil the requirements of photoacoustic (PA) imaging applications. Instead of conventional Q-switching of a single-wavelength output, rapid switching among multi-wavelength outputs in the 1600 nm region can be performed by tuning acousto-optic modulation frequencies under low-order active mode-locking conditions. The pulse repetition rate of the laser can be tuned from 200 kHz to 1 MHz, depending on the mode-locking order. In order to verify the potential of our proposed design for use in real-time PA applications, we detected PA signals generated by an absorbing target using a PA signal detection system with our dual-wavelength laser outputs.

Distributed optical fiber sensors (DOFS) based on Raman, Brillouin, and Rayleigh scattering have recently attracted considerable attention for various sensing applications, especially large-scale monitoring, owing to their capacity for measuring strain or temperature distributions. However, ultraweak backscatter signals within optical fibers constitute an inevitable problem for DOFS, thereby increasing the burden on the entire system in terms of limited spatial resolution, low measurement speed, high system complexity, or high cost. We propose a novel resonance frequency mapping for a real-time quasi-distributed fiber optic sensor based on identical weak fiber Bragg gratings (FBG), which has stronger reflection signals and high sensitivity to multiple sensing parameters. The resonance configuration, which amplifies optical signals during multiple round-trip propagations, can simply and efficiently address the intrinsic problems in conventional single round-trip measurements for identical weak FBG sensors, such as crosstalk and optical power depletion. Moreover, it is technically feasible to perform individual measurements for a large number of quasi-distributed identical weak FBGs with relatively high signal-to-noise ratio (SNR), low crosstalk, and low optical power depletion. By mapping the resonance frequency spectrum, the dynamic response of each identical weak FBG is rapidly acquired in the order of kilohertz, and direct interrogation in real time is possible without time-consuming computation, such as fast Fourier transformation (FFT). This resonance frequency spectrum is obtained on the basis of an all-fiber electro-optic configuration that allows simultaneous measurement of quasi-distributed strain responses with high speed (>5 kHz), high stability (~2.4 με), and high linearity (R2 = 0.9999).

The development of scientific technology for art authentication have elicited multidimensional evidence to distinguish forgeries from original artworks. Here, we analyzed three-dimensional morphology of cracks that contain information such as painting features of artworks using an optical coherence tomography (OCT). The forgeries were produced by an expert from the original oil paintings with cracks that occur as paint drying, canvas aging, and physical damage. The parameters such as shape, width, and depth were compared based on cross-sectional images of original and fake cracks. The shapes of original cracks were a rectangular and an inverted triangle, but fake cracks were a relatively simple inverted triangle. The original cracks were as deep as the thickness of the upper layer and mostly have ‘thin/deep' or 'wide/shallow'. The fake cracks were observed as 'thin/shallow' or 'wide/deep'. This study will improve the understanding of the crack characteristics and promote development of techniques for art authenticity.

We demonstrated a novel intensity-modulated interrogation system for an identical weak fiber Bragg grating (FBG) array based on a resonance frequency mapping technique. To compensate for the signal depletion phenomenon because of the increased reflection number of identical weak FBGs, a gain-flattening technique is employed based on the intensity modulation of the applied driving current in the optical fiber laser sensor cavity. Over 60 identical FBGs can be efficiently interrogated by detecting the resonance frequency of each FBG for a distinguished peak position.

We demonstrated the novel quasi-distributed optical fiber sensor with tens of cm spatial resolution based on the wavelength-division resonance frequency mapping technique. To interrogate a weak fiber Bragg grating (FBG) array with a reduced interval length below ~1 m, a wavelength-division optical delay system was employed to separate the adjacent reflections. In our scheme, the sensing head consists of three Bragg wavelengths in the FBG series, which are repeatedly located 15 times along the optical fiber. Thus, 45 weak FBGs can be successfully interrogated using three channels without decreasing the dynamic range of the measured strain or temperature.

Optical coherence tomography (OCT) is a noninvasive imaging modality that can provide high-resolution, cross-sectional images of tissues. Especially in retinal imaging, OCT has become one of the most valuable imaging tools for diagnosing eye diseases. Considering the scattering and absorption properties of the eye, the 1000-nm OCT system is preferred for retinal imaging. In this study, we describe the use of an akinetic swept-source OCT system based on a pulse-modulated active mode locking (AML) fiber laser at a 1080-nm wavelength for in-vivo human retinal imaging. The akinetic AML wavelength-swept fiber laser was constructed with polarization-maintaining fiber that has an average linewidth of 0.625 nm, a spectral bandwidth of 81.15 nm, and duty ratio of 90% without the buffering method. We successfully obtained in-vivo human retinal images using the proposed OCT system without the additional k-clock and the frequency shifter that provides a wide field of view of 43.1°. The main retina layers, such as the retinal pigment epithelium, can be distinguished from the OCT image with an axial resolution of 6.3 μm with this OCT system.

Oxidative stress plays a crucial role in the progression of alcoholic liver diseases and substances of antioxidant property are of special interest for therapeutic purposes. We investigated the hepatoprotective effect of leaf extracts of Sasa quelpaertensis, an edible bamboo mainly cultivated in Jeju Island, South Korea. We examined the cytotoxicity of different extracts (distilled water, 20–80% EtOH) of S. quelpaertensis on HepG2 cells and their hepatoprotective effect on HepG2 cells stimulated by ethanol (800 mM, 24 h). Furthermore, we measured reactive oxygen species (ROS) production, ethanol toxicity induced cell death, and the activity of antioxidant enzymes. In in vivo experiments, liver damage was induced by oral administration of 5 g/kg ethanol with or without potent ethanol extract of S. quelpaertensis (10 or 100 mg/kg) 12 h interval for a total of 3 doses. Only 80% ethanol extract of S. quelpaertensis (SQEE80) exhibited cytoprotective effect on HepG2 cells against alcohol-induced toxicity. SQEE80 treatment (250, 500 μg/mL) in ethanol exposed HepG2 cells showed significant attenuation of ROS production and ethanol toxicity induced cell death. Furthermore, SQEE80 markedly increased the activity of antioxidant enzyme glutathione peroxidase 1 in ethanol exposed HepG2 cells compared to ethanol stimulated cells. In in vivo experiments, SQEE80 treatment evidently suppressed the alcohol-induced histopathological changes in liver, serum ethanol content, and expression of cytochrome P450 2E1. Furthermore, SQEE80 significantly reversed the reduction of glutathione level in the ethanol challenged liver. Taken together, we suggest the possibility of developing SQEE80 as a natural hepatoprotective substance in attenuating alcohol-induced oxidative stress.

We demonstrate a novel scheme for a full-field optical coherence tomography (FF-OCT) system using a tunable-path-difference source (TPDS). Recently, the comb-spacing-swept source (CSWS) method, including TPDS, has been successfully applied to improve the stability of three-dimensional (3D) time-domain (TD)-FF-OCT imaging by eliminating the mechanical scanning of the reference path, which has been the main source of undesirable noise in general TD-OCT. However, CSWS-OCT has the drawback of a degraded signal-to-noise ratio (SNR) from a duplicated interferometer structure. In this study, we improve the configuration of the TPDS so that it can be connected directly to the measurement interferometer, including the sample and reference paths of the OCT system. In our novel TPDS-OCT, a propagating optical path through only a single interferometer was critically helpful in enhancing the SNR while retaining the benefits of CSWS-OCT, and a free-space full-field interferometer of dual-input Mach–Zehnder type also has an even higher imaging performance owing to the simultaneous exposure of optical intensity into the camera and the short image acquisition time laterally. We theoretically and experimentally demonstrated the benefits of TPDS-OCT compared with CSWS-OCT in terms of SNR. We also demonstrated 3D multi-layered imaging, which CSWS-OCT cannot achieve owing to its limited SNR.

We present a novel method for simultaneous measurement of the thickness and refractive index distribution of a transparent specimen by a line-field swept-source interferometer. In this study, by illuminating with the line-field beam instead of the point-focused beam, multiple interferences along the line-field distribution are measured simultaneously by using a combination of a novel swept source of 800-nm central region and a Si-based 1024-pixel charge-coupled device (CCD) detector. When the transparent specimen has an uneven thickness or nonuniform refractive index, the whole distribution of these two parameters can be also simultaneously measured over the illuminated region with a one-step comparison process. Using four types of transparent specimens, the thickness and refractive index distribution of each sample and a group sample paired with two specimens are accurately measured during the single wavelength scanning time of 27 ms by using the swept source with a 36-Hz sweeping rate and the CCD detector with a 36-kHz line rate.

We demonstrate dual-band wavelength-comb-swept laser for solving the aliasing interferometer signal in displacement measurement. Wavelength-comb-swept laser with etalon filter has longer coherence length and narrower linewidth than conventional wavelength-swept laser. On the other hand, aliasing of interferometer signal in displacement measurement is induced because of discrete distribution of comb spectra in wavelength domain. By using the dual-band wavelength-comb-swept-laser which has two different free spectral range (FSR) comb in each band, aliasing interferometer signal can be solved.

This study explores the effect of autopilot delay to the maximum flight range of guided projectile when the guidance command is calculated by optimization technique with considering fin deployment timing. The flight model of the guided projectile in vertical plane is developed, which includes the autopilot dynamics modeled as the first order delay system. The numerically derived optimal guidance command is scheduled to the flight simulation based on the energy height. The simulation results indicate that when we optimize the guidance command without considering the autopilot, the projectile with the time constant of the autopilot larger than 10 is not able to reach the maximum flight range. Even though autopilot delay is taken into account in the optimization process, the time constant of the autopilot may not be larger than $10^{1.5}$, otherwise the gliding performance is severely degraded. Furthermore, we show that the guided projectile with such autopilot delay is capable to reach the maximum range only with proper fin deployment timing no later than the optimal time, which is dependent on the initial state of the projectile.

Optical coherence tomography (OCT) is a noninvasive imaging modality which can provide cross-sectional imaging of the tissues in high-resolution. Especially in retina imaging, the OCT becomes one of the most valuable imaging tools for the diagnostics of the eye diseases. Considering the scattering and absorption properties of the eye, the 1000 nm OCT system is preferred for the retina image. In this study, we describe an akinetic swept source OCT system based on pulse-modulated active mode locking (AML) fiber laser at the 1080 nm wavelength region for in-vivo human retina imaging. The akinetic AML wavelength swept fiber laser is constructed with polarization maintaining fiber which has average linewidth of 0.625 nm, a spectral bandwidth of 81.15 nm and a duty ratio of 90 % without buffering method. We successfully obtained in-vivo human retina images using proposed OCT system without the additional k-clock and the frequency shifter providing wide field of view of 43.1o. The main retina layers such as RPE can be distinguished through the OCT image with axial resolution of 6.3 m.

Optical interferometry using comb-swept lasers has the advantage of efficiently reducing the acquisition bandwidth for high-speed and long-range detection. However, in general, the use of a comb-swept laser involves a critical limitation in that the absolute distance cannot be measured, and, thus, multiple layers cannot be distinguished when measuring each position. This is because of the distance ambiguity induced by optical aliasing, in which there is periodic repetition of the frequency of an interferometric signal owing to discrete spectral sweeping, which does not occur in conventional optical interferometry that uses a continuous swept laser. In this paper, we introduce an optical Vernier sampling method using a dual-comb-swept laser to measure the absolute distances in a multi-layer target. For this, we designed a new type of dual-comb-swept laser to include two different free spectral ranges (FSRs) in separated wavelength bands to provide a stable lasing condition. Using a principle similar to that of a Vernier caliper for length measurement, the two different FSRs can be used to recover a higher frequency of an optical interferometric signal to measure longer distances from different layers in a target. Using the dual-comb-swept laser in optical interferometry, we solved the optical aliasing issue and measured the absolute distances of three layers separated over 83 mm using a point-scanning imaging setup and the simultaneous absolute distance of the top surfaces separated over 45 mm using a full-field imaging setup at 14 and 8 times lower acquisition bandwidth than a conventional continuous swept laser that is based on optical interferometry.