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Osteoporosis is a well-known risk factor of screw loosening. Classically, dual-energy x-ray absorptiometry (DEXA) scan is an easy and cost-effective method of detecting bone mineral density (BMD). However, T-score on DEXA scan can be overestimated in patients with degenerative changes of the spine. Our objective was to identify correlation between Hounsfield unit (HU) measured by 3-dimensional computed tomography (3D-CT) and screw loosening.A total of 113 patients treated with lumbosacral spinal fusion were reviewed and categorized into a screw loosening group and a normal group to compare their average values of preoperative CT HU. Screw loosening was defined as radiolucent area around screw that was thicker than 1 mm with a "double halo sign".There were statistically significant differences in patient age and steroid use between screw loosening and non-loosening groups. There was no significant difference in BMD or T-score between the 2 groups. However, HU values measured in axial, coronal, and sagittal images were significantly different between the 2 groups. In the receiver operating characteristic for HU values measured in CT images, the greatest area under the curve was 0.774 and that was in case of Hounsfield unit measured by axial CT images from L1 to L4.Preoperative CT HU is associated with screw loosening. It can be a better predictor of screw loosening than DEXA scan. The best predictor of screw loosening in this study is the average value of HU from L1 to L4 in axial cut.

Cancer cells undergo unscheduled proliferation resulting from dysregulation of the cell cycle, and hence, evaluation in tumor is of keen interest to examine the invasiveness and recurrence of cancer in the lesion. Molecular probes capable of discriminating actively growing tumor from resting ones remain unexplored despite their vast importance. Here, we describe a novel strategy to visualize invasive areas in tumor with a fluorescence probe that implements synergistic fluorescence response toward the slightly acidic environment of tumor and an ATP-abundant nature of actively growing cells. The probe has been designed for ultrafast detection of ATP with high specificity. We demonstrate its utility in visualizing invasive areas in tumor by distinguishing basal cell carcinomas and squamous cell carcinomas at their early stages by two-photon microscopy.

We propose a fully-automatic deep learning-based algorithm for segmentation of ocular structures and microbial keratitis (MK) biomarkers on slit-lamp photography (SLP) images. The dataset consisted of SLP images from 133 eyes with manual annotations by a physician, P1. A modified region-based convolutional neural network, SLIT-Net, was developed and trained using P1’s annotations to identify and segment four pathological regions of interest (ROIs) on diffuse white light images (stromal infiltrate (SI), hypopyon, white blood cell (WBC) border, corneal edema border), one pathological ROI on diffuse blue light images (epithelial defect (ED)), and two non-pathological ROIs on all images (corneal limbus, light reflexes). To assess inter-reader variability, 75 eyes were manually annotated for pathological ROIs by a second physician, P2. Performance was evaluated using the Dice similarity coefficient (DSC) and Hausdorff distance (HD). Using seven-fold cross-validation, the DSC of the algorithm (as compared to P1) for all ROIs was good (range: 0.62 – 0.95) on all 133 eyes. For the subset of 75 eyes with manual annotations by P2, the DSC for pathological ROIs ranged from 0.69 – 0.85 (SLIT-Net) vs. 0.37 – 0.92 (P2). DSCs for SLIT-Net were not significantly different than P2 for segmenting hypopyons (p > 0.05) and higher than P2 for WBCs (p < 0.001) and edema (p < 0.001). DSCs were higher for P2 for segmenting SIs (p < 0.001) and EDs (p < 0.001). HDs were lower for P2 for segmenting SIs (p = 0.005) and EDs (p < 0.001) and not significantly different for hypopyons (p > 0.05), WBCs (p > 0.05), and edema (p > 0.05). This prototype fully-automatic algorithm to segment MK biomarkers on SLP images performed to expectations on an exploratory dataset and holds promise for quantification of corneal physiology and pathology.

Hypoxia, a condition of oxygen deficiency in tissues, features various diseases including solid tumor. Under hypoxia, several reductases such as nitroreductases are elevated. Based on this fact, we have investigated an indirect way to assess the hypoxia susceptibility of different organ tissues (mouse lung, heart, spleen, kidney, and liver) by detecting nitroreductase present within. Among the organs, the kidney showed a notable susceptibility to hypoxia, which was due to the renal medulla, not due to the renal cortex, as observed by ratiometric fluorescence imaging with a probe. The probe features ratiometric signaling, NIR-emitting, two-photon absorbing, and pH-insensitive emission properties, offering a practical tool for studying the nitroreductase activity and, furthermore, hypoxia-associated biological processes.

Purpose To evaluate the reliability of manual annotation when quantifying cornea anatomical and microbial keratitis (MK) morphological features on slit-lamp photography (SLP) images. Methods Prospectively enrolled patients with MK underwent SLP at initial encounter at 2 academic eye hospitals. Patients who presented with an epithelial defect (ED) were eligible for analysis. Features, which included ED, corneal limbus (L), pupil (P), stromal infiltrate (SI), white blood cell (WBC) infiltration at the SI edge, and hypopyon (H), were annotated independently by 2 physicians on SLP images. Intraclass correlation coefficients (ICCs) were applied for reliability assessment; dice similarity coefficients (DSCs) were used to investigate the area overlap between readers. Results Seventy-five MK patients with an ED received SLP. DSCs indicate good to fair annotation overlap between graders (L = 0.97, P = 0.80, ED = 0.94, SI = 0.82, H = 0.82, WBC = 0.83) and between repeat annotations by the same grader (L = 0.97, P = 0.81, ED = 0.94, SI = 0.85, H = 0.84, WBC = 0.82). ICC scores showed good intergrader (L = 0.98, P = 0.78, ED = 1.00, SI = 0.67, H = 0.97, WBC = 0.86) and intragrader (L = 0.99, P = 0.92, ED = 0.99, SI = 0.94, H = 0.99, WBC = 0.92) reliabilities. When reliability statistics were recalculated for annotated SI area in the subset of cases where both graders agreed WBC infiltration was present/absent, intergrader ICC improved to 0.91 and DSC improved to 0.86 and intragrader ICC remained the same, whereas DSC improved to 0.87. Conclusions Manual annotation indicates usefulness of area quantification in the evaluation of MK. However, variability is intrinsic to the task. Thus, there is a need for optimization of annotation protocols. Future directions may include using multiple annotators per image or automated annotation software.

Purpose To evaluate the recipient factors associated with graft detachment in the subsequent eye of patients who underwent sequential Descemet membrane endothelial keratoplasty (DMEK). Methods A retrospective, consecutive case series with 158 eyes of 79 patients who underwent DMEK surgeries in both eyes between October 2013 and April 2019 for treatment of Fuchs endothelial dystrophy. The main outcome measure was the presence of graft detachment (any amount of detachment) at postoperative 1 week in the subsequent eye. Preoperative, intraoperative, and postoperative factors were evaluated for association with graft detachment. Results Of 79 patients (158 eyes) with a mean follow-up of 11.7 ± 8.4 months, 18 patients (36 eyes) developed graft detachment in both eyes 1 week postoperatively. The risk of detachment in the subsequent eye was increased when the first eye had any amount of detachment [odds ratio = 2.8; 95% confidence interval (CI) = 1.1-7.3; P = 0.037]. When the first eye had a clinically significant detachment (>30% detached), the risk of detachment occurring in the subsequent eye was greater (odds ratio = 15.7; 95% CI = 1.8-134.5; P = 0.012). This risk of graft detachment in the subsequent eye increased 33% for every 5% increase in the detachment percentage in the first eye (odds ratio = 1.3; 95% CI = 1.1-1.6; P = 0.008). Conclusions The presence of graft detachment after DMEK increases the risk of graft detachment in subsequent DMEK in the contralateral eye. Modification in perioperative care and surgical technique in the contralateral eye, such as a larger gas bubble, use of SF6 20%, and combining cataract surgery, may be needed when graft detachment occurs after DMEK in the first eye.

Purpose of review As keratoconus is a chronic disease affecting young people, vision-related quality of life is often significantly impaired in patients with this disease. However, successful management of keratoconus, including visual rehabilitation strategies, can improve quality of life in these patients. This review will describe clinical approaches that improve vision-related quality of life in patients with stable keratoconus. Recent findings Several types of contact lenses including scleral lenses have been used successfully to manage keratoconus. Eyes with severe keratoconus, even those in which fitting with other types of lenses is challenging, can be successfully fitted with scleral lenses. Although laser ablative procedures, such as photorefractive keratectomy (PRK) have been traditionally contraindicated in patients diagnosed with or suspected of having keratoconus, PRK has been attempted to partially correct refractive errors in keratoconus. Although phototherapeutic keratectomy and radial keratotomy have been reported to be used in eyes with keratoconus, effectiveness and safety results have varied. Implantation of phakic intraocular lenses and intraocular lenses, including toric intraocular lenses, which primarily correct regular astigmatism, with cataract extraction or refractive lens exchange can improve vision-related quality of life in patients with keratoconus by significantly reducing cylinder while improving uncorrected visual acuity. Summary Appropriate selection and application of treatment options based on consideration of multiple factors will help patients with keratoconus, improving their vision-related quality of life and delaying or avoiding keratoplasty.

As attractive photoactive materials, metal halide perovskites demonstrate outstanding performance in a wide range of optoelectronic applications. Among the various compositions studied, mixed-halide perovskites have a finely tunable band gap that renders them desirable for targeted applications. Despite their advantages, photoinduced halide segregation often deters the photoelectric stability of the materials. Herein, we adopt a strategy of post-treating the perovskite surface with an organic spacer to generate a two-dimensional (2D) perovskite passivating layer. Trap-assisted recombination pathways can be selectively modulated by passivating the surface halide defects that cause photoinduced halide segregation. Fluorescence lifetime imaging of flat and bent surfaces of perovskites reveals that the perovskite lattice tolerates mechanical strain via the neutralizing passivation of ionic halide defects. Upon bending, the photocurrent response of the flexible photodetector is maintained over 83% for 2D passivated perovskite and drops to 23% for pristine perovskite. A flexible photodetector array built with 2D passivated perovskite, in combination with a deep learning algorithm, demonstrates excellent accuracy in determining letters of the alphabet for both flat (96%) and bent (93%) states. The connection of chemically modified charge carrier dynamics and mechanical properties revealed in this study offers valuable guidance for developing next-generation optoelectronic applications.

With the growing interest in wearable devices in recent decades, considerable effort has been devoted to developing mechanical elastomeric devices such as sensors, transistors, logic circuits, and integrated circuits. To successfully implement elastomeric devices subjected to large mechanical deformations or stretching, all the components, including conductors, semiconductors, and dielectrics, must have high stability and mechanical sustainability. Elastomeric conductors, which exhibit excellent electrical performances under mechanical deformations, are key components of elastomeric devices. Herein, we prepared fully elastomeric electrodes based on interconnected 2D gold nanosheets (AuNSs) to develop mechanically resilient integrated electronics. The AuNS elastomeric electrodes exhibited a sheet resistance of less than 2 Ω/sq under 50% stretching and sustained 100,000 stretching–releasing cycles. These electrodes with a dedicated design were used in combination with elastomeric semiconductors of P3HT nanofibrils in the PDMS elastomer (P3NF/PDMS) and an ion gel as a dielectric to realize elastomeric transistors, inverters, and NOR and NAND logic gates. Additionally, an elastomeric 8 × 8 transistor array that can sustain various types of mechanical stimuli was successfully demonstrated. Furthermore, the elastomeric electronic devices implemented on a soft robot showed no interfering performances during robot gripping motion. The proposed framework is expected to aid in the rapid development and broaden the application scope of soft electronics.

Reactive oxygen species (ROS) produced by an inflammatory response in the brain are associated with various neurological disorders. To investigate ROS-associated neuroinflammatory diseases, fluorescent probes with practicality are in demand. We have investigated hypochlorous acid, an important ROS, in the brain tissues of neuroinflammation and maternal immune activation (MIA) model mice, using a new fluorescent probe. The probe has outstanding features over many known probes, such as providing two bright ratio signals in cells and tissues in deep-red/near-infrared wavelength regions with a large spectral separation, in addition to being strongly fluorescent, photo- and chemo-stable, highly selective and sensitive, fast responding, and biocompatible. We have found that the level of hypochlorous acid in the brain tissue of a neuroinflammatory mouse model was higher (2.7-4.0-fold) compared with that in normal brain tissue. Furthermore, the level of hypochlorous acid in the brain tissue of a MIA mouse model was higher (1.2-1.3-fold) compared with that in the normal brain tissue. The "robust" probe provides a practical tool for studying ROS-associated neurological disorders.

PURPOSE The purpose of this study was to determine the safety of long-term storage and shipping of prestripped, prestained, and preloaded Descemet membrane endothelial keratoplasty (pDMEK) grafts. METHODS A total of 33 cadaveric corneas were prestripped, prestained, and preloaded using modified Jones tube injectors as pDMEK. The corneas were masked to groups that were prepared

LNG Combined Heat and Power(CHP) has the more efficient advantage over the separate supply of heat and electricity to the customers resulting from generating heat and power simultaneously. Therefore it is known as the high efficient equipment and can reduce total gas consumption from national perspective. Most of papers on the CHP economic analysis are written from the financial perspective of company itself. From the perspective of company, sales revenue analysis based on revenue and expenditure in terms of electric charge plays the important role in benefit-cost analysis. However this paper presents the economic analysis based on the benefit-cost analysis of CHP from national perspective. The result shows that only high capacity CHP, especially 500MW, is more economical than typical fossil-fired generators and gas boilers.

Purpose To evaluate visual outcome and patient satisfaction following implantation of multifocal intraocular lenses (IOLs) with a +1.5 diopters (D) addition compared with monofocal IOLs. Methods This prospective, nonrandomized, comparative case series involved 48 eyes (24 patients) who underwent cataract surgery with implantation of low-power-added multifocal IOLs (LS313-MF15; multifocal group) and 48 eyes (24 patients) with conventional monofocal IOLs (CTS204; monofocal group). Visual acuity (VA), defocus curves, refraction, contrast sensitivity, glare, ocular optical quality, and scores in questionnaire were assessed 6 months postoperatively. Results Uncorrected VA at intermediate and near distance tended to be better in the multifocal group, with significant differences at 50 cm (P=0.03). The defocus curve showed significantly different VA at vergences of -1.5 and -2.0 D (P=0.02 and P=0.03, respectively). Results of postoperative refraction, contrast sensitivity, glare, and optical quality were similar (P>0.05), although coma-like aberration was higher in the multifocal group (P=0.04). Despite of similar levels of visual disturbances (P>0.05), disturbances in activities and spectacle use at intermediate working distance were significantly less frequent in the multifocal group (P=0.03 and P=0.04, respectively). Multifocal group showed significantly greater overall satisfaction (P=0.02). Conclusions Low-power-added multifocal IOLs yielded better intermediate and near vision without increasing optical phenomena compared with monofocal IOLs.

Purpose To assess variability in corneal ulcer measurements between ophthalmologists and reduce clinician-dependent variability using semiautomated segmentation of the ulcer from photographs. Methods Three ophthalmologists measured 50 patients' eyes for epithelial defects (EDs) and the stromal infiltrate (SI) size using slit-lamp (SL) calipers. SL photographs were obtained. An algorithm was developed for semiautomatic segmenting of the ED and SI in the photographs. Semiautomatic segmentation was repeated 3 times by different users (2 ophthalmologists and 1 trainee). Clinically significant variability was assessed with intraclass correlation coefficients (ICCs) and the percentage of pairwise measurements differing by ≥0.5 mm. Semiautomatic segmentation measurements were compared with manual delineation of the image by a corneal specialist (gold standard) using Dice similarity coefficients. Results Ophthalmologists' reliability in measurements by SL calipers had an ICC from 0.84 to 0.88 between examiners. Measurements by semiautomatic segmentation had an ICC from 0.96 to 0.98. SL measures of ulcers by clinical versus semiautomatic segmentation measures differed by ≥0.5 mm in 24% to 38% versus 8% to 28% (ED height); 30% to 52% versus 12% to 34% (ED width); 26% to 38% versus 10% to 32% (SI height); and 38% to 58% versus 14% to 34% (SI width), respectively. Average Dice similarity coefficients between manual and repeated semiautomatic segmentation ranged from 0.83 to 0.86 for the ED and 0.78 to 0.83 for the SI. Conclusions Variability exists when measuring corneal ulcers, even among ophthalmologists. Photography and computerized methods for quantifying the ulcer size could reduce variability while remaining accurate and impact quantitative measurement endpoints.

To report results of multifocal intraocular lens (IOL) implantation in 2 patients with refractive error and presbyopia after previous radial keratotomy (RK). A refractive multifocal IOL with rotational asymmetry (LS313-MF30; Oculentis, Berlin, Germany) was implanted. The first patient was a 60-year-old man with myopia who underwent unilateral RK 20 years before. His uncorrected distance visual acuity (UDVA) was 20/400, and his distance corrected near vision was J9 in both eyes. Six months after bilateral surgery, his binocular UDVA and uncorrected near visual acuity (UNVA) improved to 20/20 and J1, respectively, although he experienced diurnal fluctuation. The second patient was a 55-year-old woman with hyperopia who underwent bilateral RK 18 years before. Uncorrected distance visual acuity was 20/25 in both eyes, but UNVA was between J9 and J10. Three months after unilateral surgery, UDVA and UNVA of the postsurgical eye improved to 20/20 and J1, respectively. Neither patient reported any significant photic phenomena, and both were satisfied with the results of treatment. The desirable clinical outcomes and levels of satisfaction expressed by these patients indicate that surgery using this particular multifocal IOL may benefit presbyopic patients with previous RK. This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND), which permits downloading and sharing the work provided it is properly cited. The work cannot be changed in any way or used commercially.

A state of limbal stem cell deficiency (LSCD) can be secondary to a number of etiologies, resulting in either a reduction in the total number of limbal stem cells or an abnormality in stem cell function. Initially, the epithelium becomes irregular and hazy; however, this condition may progress to persistent corneal epithelial defects, stromal scarring, ulceration, and even perforation. Since LSCD secondary to a variety of etiologies may be reversible, and various factors are prognostic of disease progression, timely diagnosis is important. This review will describe current knowledge of diagnostic techniques for LSCD and understanding of epithelial stem cell function.Conjunctivalization, regarded as the most reliable clinical finding diagnostically, can be identified as late staining of epithelium with fluorescein. While identifying loss of the palisades of Vogt by slit-lamp examination, can provide a high suspicion of LSCD, but this is not diagnostic. Impression cytology is a simple, noninvasive technique that aids in the diagnosis of LSCD, but a negative result also cannot rule out the diagnosis. Recent findings have also shown that imaging techniques including in-vivo confocal microscope and optical coherent tomography can also aid in diagnosing LSCD; however, several challenges remain before these techniques become standard diagnostic methods in clinical practice. Meanwhile, determination of the absence of limbal epithelial crypts and focal stromal projections using image reconstruction techniques may assist in the diagnosis of LSCD. Furthermore, histologic markers may help not only to improve sensitivity and specificity of conventional techniques in diagnosis of LSCD, but also to identify human limbal stem cells and determine their number and function in LSCD.Efforts to develop and improve techniques for diagnosing LSCD are ongoing. Increased knowledge of limbal stem cells and components of their niches may not only help in understanding the pathogenesis of LSCD but may improve its diagnosis, thereby ameliorating the prognosis of patients with this devastating disease.

Objective Chronic low back pain (CLBP) often causes disabling pain that impairs a patient's quality of life. Surgical treatment is recommended for patients who do not respond to conservative treatments lasting more than 6 months. The purpose of this study is to present results after the use of an interlaminar dynamic spacer for CLBP. Methods We enrolled consecutive patients with CLBP irresponsive to more than 6 months of conservative treatment into the present study. Included patients underwent an interlaminar dynamic spacer insertion without direct decompression. We assessed radiographic parameters and health-related quality of life (HRQoL) data included visual analog scale back/leg pain and Oswestry Disability Index scores. Substantial clinical benefit achievement was assessed. Results Thirty-five patients (average age, 47.8 years; 21 female) were included. The mean preoperative symptom duration was 29.6 months. Surgeries involved 1-level (n = 18) and 2-levels (n = 17) procedures. Operative levels included L4-5 (n = 8), L5-S1 (n = 10), L3-4-5 (n-2), and L4-5-S1 (n = 15). The average follow-up period was 16.6 months. After the procedure, all radiographic parameters (including disc height, segmental extension angle, and foraminal area) improved significantly. All preoperative HRQoL parameters improved significantly at the final follow-up. Substantial clinical benefit achievement was observed in 75.8% of the cases on the Oswestry Disability Index, and in 72.7% and 84.8% of the cases on the visual analog scale back and leg pain, respectively. Conclusions An interlaminar dynamic spacer significantly improves HRQoL scores in patients with CLBP who do not respond to conservative treatment. Although encouraging, these results should be confirmed with studies assessing a larger cohort and a longer follow-up.

OBJECTIVES To evaluate the clinical outcomes of patients with limbal stem cell deficiency (LSCD) who were fitted with the Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) scleral device. METHODS In this retrospective, interventional case series, we reviewed the charts of 31 eyes of 19 consecutive patients clinically diagnosed with LSCD who were evaluated for the PROSE device. Clinical data were reviewed before PROSE evaluation and at the last available follow-up. The main outcomes measures were best-corrected distance visual acuity (CDVA) and modified ocular involvement score (OIS), graded using a previously described system for corneal findings. RESULTS Corrected distance visual acuity improved from 0.86±0.50 logarithm of the minimal angle of resolution (Snellen equivalent, 20/145) at baseline to 0.46±0.44 (Snellen equivalent, 20/58) with PROSE at the last follow-up (mean, 25.1±18.0 months; P

This study sampled endangered species, Lamprotula coreana, and surveyed its habitat at the Guem River with three times from June to August 2013. To assess the habitat, this study conducted field survey considering diverse physical conditions of stream, such as pool, run and riffle, and measured transect, water depth, water velocity, substrate structure, and habitat type. When L. coreana collected, length, weight and age were measured. Water velocity, water depth and substrate structure were recorded to develop HSI (habitat suitability index) and performed PHABSIM (physical habitat simulation) to estimate the optimum flow discharge. Water level, flow discharge and transect data were used for habitat assessment, and PHABSIM was applied to calculate WUA (weighed usable area). Shell length was 73.1 ± 18.4 mm (28.5-102.0 mm), shell weight was 131.6 ± 72.3 g (28.0-281.0 g) and age was two to seven years from L. coreana collected at the upstream of the Guem River. Developed HSI indicated that the optimal habitat for L. coreana was 0.4-0.5 m for water depth, 0.3-0.5 m/s for water velocity and sand to boulder for substrate structure. The optimum ecological flow discharge for L. coreana was 2.1 cms and WUA was 3,730 m 2 /1000 m by the result of PHABSIM. Recently, river construction work and habitat disturbance have caused negative impact on the distribution of L. coreana. The result of this study would provide fundamental data for habitat restoration and management of L. coreana.

Combined anterior and posterior surgery is frequently chosen for the treatment of prior, severe C1–2 dislocations that occurred during early childhood because of the difficulty in achieving reduction and satisfactory decompression. The authors treated a prior, severe C1–2 dislocation that was causing progressive quadriparesis. The patient was a 14-year-old boy who had suffered a C1–2 fracture-dislocation at 3 years of age and had been treated with a Minerva body jacket cast. The treatment involved posterior C1–2 segmental screw fixation, without direct bone decompression or additional surgery. Satisfactory neural decompression was achieved with the techniques used, and complete bone union was confirmed. The patient showed satisfactory neurological recovery at the 5-year follow-up assessment.

일반적으로 효율적인 착륙장치의 설계는 착륙장치의 성능 및 전기체의 구조적 안전성을 위해 매우 중요한 요소이다. 일반적으로 항공기의 착륙장치는 전체 비행기 무게의 4 ~ 7% 정도를 차지하지만, 전 기체의 4 ~ 5배 수준에 달하는 착륙하중과 여러 지상운용 하중을 지지해야 한다. 항공기의 착륙 시에는 지면과 닿는 순간 많은 하중이 기체에 전달되는데 착륙장치는 이러한 하중이 항공기 동체에 직접적으로 전달되지 않도록 지면으로 부터의 충격이나 진동을 상당량 흡수하는 역할을 하게 된다. 따라서 착륙장치는 항공기의 안전성 확보를 위해 매우 중요한 부분이다. 항공기 착륙장치는 항공기가 지상에 닿는 순간부터 다시 떠오르는 순간까지 (매우 다양한 하중을 겪게 된다.2) Key Words: Landing Gear(착륙장치), Plate Spring(판스프링), Composite Material(복합재료), Margin of Safety(안전계수) 초록: 오늘날 비행기는 없어서는 안 되는 교통수단 중의 하나이다. 비행기는 교통 수단 뿐 만 아니라 여러 분야에서 널리 사용되고 있다. 예를 들어, 사람을 태우고, 짐을 실어 나르고, 군에서는 정찰 등의 임무를 수행하게 된다. 지상에서 이륙∙착륙이 이루어 진다. 이륙할 때 보다는, 착륙할 시 랜딩기어에 많은 하중이 작용하게 된다. 착륙장치는 충격 에너지를 흡수하며, 사고 시에 동체가 파손되지 않도록 방지한다. 본 논문에서는 복합재와, 알루미늄을 적용한 판 스프링형 랜딩기어에 대하여 시뮬레이션을 수행하였다. 두 가지 재료의 랜딩기어에 대한 구조적 안전성이 평가되었다. Abstract: Aircraft are an indispensable mode of modern transportation. They are also used as in a wide variety of other fields. For example, aircraft are used for accommodating passengers, carrying freight, and for military reconnaissance. Aircraft ground operations include landing and taking off. During landing, a higher load is applied to the landing gear than during takeoff. The landing gear should absorb impact energy and prevent damage to the main body of the aircraft in the case of an accident. In this study, simulations were performed for two types of plate-spring-type landing gear: that made of composite materials and that constructed with aluminum. The structural safety of landing gear made of each material was also evaluated.

Study design A retrospective study. Purpose To evaluate the prevalence and risk factors of asymptomatic cervical or thoracic lesions in elderly patients who have undergone surgery for lumbar spinal stenosis. Overview of literature Concurrent multiple spinal lesions have been reported in many studies with a varied prevalence, and described the characteristics of the disease and its treatment options. However, the cervical or thoracic lesions without apparent symptoms in patients with symptomatic lumbar stenosis had not been evaluated. Methods A total of 101 elderly patients (aged 65 or more), who had undergone surgery for lumbar spinal stenosis from January 2005 to December 2005, were enrolled in this study. All patients underwent lumbar magnetic resonance imaging (MRI) along with T2-weighted cervical and thoracic sagittal MRI prior to surgery. The concurrent cervical or thoracic lesions were classified according to the disease entity, and the severity of the lesions was graded from grade 0 (no lesion) to grade 4 (any lesion compressing the cord with a signal change). The prevalence of concurrent cervical and thoracic lesions was then analyzed. In addition, the risk factors for the development of concurrent lesions were evaluated, and the risk factors affecting the severity of the concurrent lesion were analyzed individually. Results Seventy-seven (76.2%) and 30 (29.7%) patients had a concurrent cervical and thoracic lesion, respectively. Twenty-six patients (25.7%) had both a cervical and thoracic lesion. There was a positive correlation between the symptom duration of lumbar stenosis and the prevalence of both cervical (p = 0.044) and thoracic (p = 0.022) lesions. Conclusions The incidence of asymptomatic cervical or thoracic lesions is apparently high in elderly patients who have undergone surgery for lumbar spinal stenosis, particularly in those with longer symptom duration. This highlights the need for a preoperative evaluation of the cervical and thoracic spine in these patients.