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Background/Aims: Despite improvements in surgical techniques and postopera tive patient care, bile leakage can occur after hepatobiliary surgery and may lead to serious complications. The aim of this retrospective study was to evaluate the efficacy of endoscopic treatment of bile leakage after hepatobiliary surgery. Methods: The medical records of 20 patients who underwent endoscopic retro grade cholangiopancreatography because of bile leakage after hepatobiliary sur gery from August 2009 to September 2014 were reviewed retrospectively. Endo scopic treatment included insertion of an endoscopic retrograde biliary drainage stent after endoscopic sphincterotomy. Results: Most cases of bile leakage presented as percutaneous bile drainage through a Jackson-Pratt bag (75%), followed by abdominal pain (20%). The sites of bile leaks were the cystic duct stump in 10 patients, intrahepatic ducts in five, liv er beds in three, common hepatic duct in one, and common bile duct in one. Of the three cases of bile leakage combined with bile duct stricture, one patient had severe bile duct obstruction, and the others had mild strictures. Five cases of bile leakage also exhibited common bile duct stones. Concerning endoscopic modal ities, endoscopic therapy for bile leakage was successful in 19 patients (95%). One patient experienced endoscopic failure because of an operation-induced bile duct deformity. One patient developed guidewire-induced microperforation during cannulation, which recovered with conservative treatment. One patient developed recurrent bile leakage, which required additional biliary stenting with sphincter -otomy. Conclusions: The endoscopic approach should be considered a first-line modality for the diagnosis and treatment of bile leakage after hepatobiliary surgery.

This paper presents an altitude detection accuracy for long range and multifunction radar. The accuracy is difficult to estimate because it is affected by an time varying atmosphere refractivity. We analyze altitude accuracy with a raytracing simulator with atmosphere refractivity. An altitude error is simulated with measured and modeled refractivity, and the modeled refractivity is used for compensate an altitude accuracy. As a result, the error is modeled with normal distribution function, and analyzed.

A simple and exact closed-form equation to determine a penetrated ray path in a ray tracing is proposed for an accurate channel prediction in indoor environments. Whereas the penetrated ray path in a conventional ray tracing is treated as a straight line without refraction, the proposed method is able to consider refraction through the wall in the penetrated ray path. Hence, it improves the accuracy in ray tracing simulation. To verify the validation of the proposed method, the simulated results of conventional method, approximate method, and proposed method are compared with the measured results. The comparison shows that the proposed method is in better agreement with the measured results than the conventional method and approximate method, especially in high frequency bands.

In this paper, an exponential model of Korea is proposed to minimize an altitude-error of high-altitude target due to atmosphere refraction at radar system. The relation between surface refractivity and refractivity gradient, which is extracted using the least square fit from the measured data at 7 weather stations, is applied to the exponential model. And in order to verify the proposed model, the altitude-errors for a standard atmosphere, a CRPL(Central Radio Propagation Lab.) exponential model, the proposed model are extracted and analyzed using a ray tracing. As a result, the proposed model can improve the altitude estimation performance of radar compared to conventional atmosphere refractive index models.

In this paper, an interference analysis method with a site-specific path loss model for a wireless personal area network (WPAN) is proposed. The site-specific path loss model is based on geometrical optics and geometric probability to consider both site-specific radio propagation characteristics and a closed-form expression to obtain the mean interference from which the uniformly distributed multiple interferers are derived. Therefore, the proposed interference analysis method can achieve more computational simplicity than the Monte-Carlo (MC) simulation, which uses the ray-tracing (RT) technique. In addition, better accuracy than the conventional interference analysis model that uses stochastic method can also be achieved. To evaluate the proposed method, a signal to the interference-noise ratio with a mean interference concept for uniformly distributed interferers is calculated and compared in two simulation scenarios. As a result, the proposed method produces not only better matched results with the MC simulation using the RT technique than the conventional interference analysis model, but also simpler and faster calculation, which is due to the site-specific path loss model and closed-form expression for interference calculation.

In this paper, a SIT(Source Independent Tree) method for ray tracing is proposed to enhance the efficiency of tree construction with reuse of sub tree in urban environment, As the SIT method is applied, the decrease of the number of nodes for picocell and microcell simulations is 100 times. And 88~98 % of the total nodes are reused with change of location of signal source from an analysis of node reuse efficiency. Therefore the proposed SIT method is useful in performance enhancement of ray tracing, especially, for multiple antenna simulation like as MIMO system and cell planning.

In this paper, we proposed an improved ray tracing method with an amelioration of visible tree structure, a visible face determination method, and non-uniform random test point method. In a proposed visible tree structure, it reduces tree nodes by means of merging similar nodes. In a visible face determination method, it shows that a ray hit test with a packet ray method can reduce a test time. A ray tracing method involving with a packet ray hit test method can improve a tree construction time up to 3.3 times than a ray tracing method with a single ray hit test method. Furthermore, by seeding a non-uniform and random test point on a face, tree construction time is improved up to 1.11 times. Received powers from the proposed ray tracing results and measured results have good agreement with 1.9 dB RMS error.

In this work, a new method to obtain the effective ground conductivity value in the middle frequency band where the informations of soil characteristics are insufficient was proposed. The proposed method obtained the effective ground conductivity values with the measured field strength from sea reference stations and general attenuation model in the middle frequency band. In addition, the proposed method used statistical method to minimize the error between the measurements and the predictions. Then, the effective ground conductivity in Korea peninsular was obtained by using the proposed method. Finally, it was verified that the effective ground conductivity using the proposed method is useful to predict electric field strength in the middle frequency band.

To predict the system coverage in the middle frequency(MF) band, it is required to know the antenna efficiency at a base station. However, calculating the accurate efficiency is difficult since the efficiency may change according to the area where the antenna is installed. Thus, this paper proposes a method to obtain the antenna efficiency of a base station in the MF band from the measurement. This method uses the measured field strengths and the attenuation model in the MF band. Therefore, an attenuation model which is used in the proposed method is presented at first. Then, the process of the proposed method is followed using detailed explanations. Finally, antenna efficiencies of base stations which are currently operating are obtained by applying the proposed method and the usefulness of the obtained results are verified by comparing with ideal efficiencies.

The prediction of a system coverage is required to install or operate a base station of the differential global positioning system(DGPS). However, the predicted results differ from the measured results when those are analyzed using ITU-R effective ground conductivity values. Thus, in this paper, the coverages of DGPS reference stations are analyzed using the modified effective ground conductivity values. The modified effective ground conductivity is based on the effective ground conductivity of ITU-R and modified to minimize the error between the measured electric fields and the predicted electric fields by using a statistical method. Then, the DGPS system coverages are analyzed by using the modified effective ground conductivity values, and the system stability is verified with a various analysis.

In this paper, a wideband lens amplifier is proposed as a spatial power combiner for C-band services. The proposed lens amplifier has a tile-tray hybrid structure that can solve isolation, wideband, and heat-sink problems. Also, it has a balanced amplifier structure which has many benefits, such as high output power, but remains a simple circuit configuration without a balun. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 148–152, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20927

In this paper, a small-chip meander antenna for dual-frequency operation is presented. This novel compact dual-frequency antenna uses a meander patch with increased capacity to adjust dual operating frequencies with small size and frequency ratio. The proposed antennas are fabricated by the LTCC-MLC process. The characteristics of return losses, radiation patterns, and gains are discussed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 274–277, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10580

The steady-state of a propagation eccentric crack in a piezoelectric ceramic strip bonded between two elastic materials under combined anti-plane mechanical shear and in-plane electrical loadings is considered in this paper. The analysis based on the integral transform approach is conducted on the permeable crack condition. Field intensity factors and energy release rate are obtained in terms of a Fredholm integral equation of the second kind. It is shown for this geometry that the crack propagation speed has influence on the dynamic energy release rate. The initial crack branching angle for a PZT-5H piezoceramic structure is predicted by the maximum energy release rate criterion.

An inset-fed antenna with a shorting pin and slots is presented for harmonic suppression of an active integrated antenna. Its fundamental resonant frequency is 5.8 GHz. At fundamental and harmonic frequencies, return loss and radiation characteristics are measured and compared with those of the conventional microstrip patch antenna. The second and third harmonic return losses of the proposed antenna are suppressed to 6.7 dB and 17.7 dB with respect to the conventional patch antenna, respectively.

The proposed dual-feeding active integrated antenna suppresses the third harmonics and isolates the Tx signal at the Rx ports to a high degree. The characteristics of the measured results are provided and the transmitted output power of the 2 × 2 array for the spatial power combining effect is calculated. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 435–437, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10487

In this paper, we propose an efficient ray tracing method based on a 4-ray model considering a real urban canyon environment characterized by building distributions. In order to reduce the computing time, reduce the complexity of the ray tracing algorithm, and easily apply the method to an existing GIS containing building information, the relationship between the 4-ray model and a roadside building width index (BWI) relating to the building distribution information around the received signal is considered. The modified 4-ray model can efficiently estimate propagation characteristics, including path loss and fading, in an urban canyon environment.

In this paper, extended GBSBEM is proposed for indoor LOS MIMO channel using polarization diversity at 8 GHz bands. The proposed model can create spatial channel parameters for each environment. It extends to have 3-dimensional geometry for indoor environment and consider array antennas using spatial correlation, also. In addition, scattering mechanism as well as reflection is considered using the patch scattering model. And to verify the proposed model results, which measured at small office room and corridor, are compared with simulated results.

A ray-tracing method in conjunction with UTD (uniform theory of diffraction) has been widely used to characterize a wireless communication channel. Due to the complexity of the real situation, the ray-tracing method generally assumes buildings have homogeneous and smooth surfaces. However, in a real case, the building surface consists of many heterogeneous materials, whose shapes are also various. Hence, the scattering by the surface is much different from a homogeneous surface, which will affect the final accuracy of the ray-tracing method. In UTD, scattering mechanism by an object is mainly decomposed into two groups: reflection and diffraction. In general, the reflection in the specular direction is important, but the inhomogeneity may reduce the specular reflection drastically. In this paper, to consider the reduction of the specular reflection, we formulate the effective specular reflection based on PO (physical optics) approximation, and include the reflection in a 3D ray-tracing code. Then, we investigate the inhomogeneity effect on the final path-loss.

This work presents a quasi-three dimensional MIMO channel model to predict the polarization characteristics of an indoor radio channel. The model considers not only the effects of the polarization of the transmitting and receiving antenna elements, but also the types of indoor environment scatterers. The proposed model is based on an ellipse model and a patch scattering model. Furthermore, the channel model expands the ellipse model to a quasi-three dimensional model. The proposed model is suitable for indoor MIMO channels and can expect ergodic capacities of a multi-polarized MIMO channel, which considers polarization and 3-D geometry.

Recently, beyond 3G systems have been drawing a great deal of attention concerning next generation wireless services that provide 100 Mbps at high mobility and 1 Gbps at nomadic mobility environment. In order to exploit new mobile radio spectrum resource below 6 GHz bands in Korean radio environment, the first important step consists in a proper understanding of propagation characteristics in candidate bands. Therefore, we propose a channel model which is based on measured path loss data in various topographic areas of Seoul metropolitan city at 5.3 GHz and 2.1 GHz bands. The proposed model is a modified 4-ray model which can consider road side building characteristics in urban street canyon LOS environment. Compared to 4-ray model, it can predict path loss more accurately

A correlation function for partially correlated waves and hallway angular response model is proposed. The deterministic hallway angular response model is used to determine incident magnitude at arbitrary angle. With that angular response, the partially correlated correlation function is investigated. Correlated and uncorrelated waves are classified with physical characteristics of incident waves. The proposed correlation function and the angular response model can provide a correlation in a specific geometry of propagation environment and electrical parameters of the environment in a hallway because the model is a function of the ratio of hallway width to Tx-Rx distance and electrical wall characteristics.

In this paper, a non-constant serpentine TM/sub 01/ to TE/sub 11/ mode converter with short length for X-band high power microwave applications is presented. The mode converter is designed to operate at 10 GHz and utilize the structure of circular waveguide with an excessive curvature in order to convert efficiently between two modes. To achieve optimum design, the basic parameters are calculated by the approximation method proposed in this paper and optimized by the FIM simulator.

In this paper, an indoor propagation channel model for a MIMO (multi-input multi-output) system at the 5 GHz band is presented. 3D ray tracing and a patch scattering model are primarily used in order to take the indoor fixtures into account. Therefore, input parameters, such as indoor environment parameters and types of antenna are considered. In the results, the PDP (power delay profile) and AOA (angle of arrival) are presented, and the RDS (RMS delay spread) and AS (angular spread) are calculated from them. In order to verify the accuracy of the proposed model, simulated results are compared with measurements in an actual indoor environment. Estimated eigenvalues for MIMO channel characteristics are also represented.

Carpal tunnel syndrome is the most common peripheral entrapment neuropathy. We report on the first Korean case of carpal tunnel syndrome induced by tophaceous deposition in flexor digitorum tendons of a patient with chronic gout. A 63-year-old male suffered from numbness, decreased sensation over both median nerve distribution, and weakness of thenar muscle for 3 years. Physical examinations revealed positive Tinel’s sign and Phalen’s test and thenar qjmuscle atrophy was found on both hands. In nerve conduction study, there was no action potential of the sensory and motor of the bilateral median nerve. Ultrasonography showed increased cross-sectional area of median nerve due to tophaceous deposition in flexor digitorum tendons in the carpal tunnel. Dual-energy computed tomography showed diffuse multifocal green color coding tophaceous deposition within the carpal tunnel. His neuropathic symptoms improved after injection of triamcinolone into the carpal tunnel and administration of oral medication including non-steroidal anti-inflammatory drugs and colchicine. (J Rheum Dis 2015;22:29-33)

Recently active integrated antennas have been studied for more efficiency and harmonic reduction. The designed antenna provides a good radiation pattern on resonant frequency, and reduces EMI by suppression of second and third harmonics. Also it increases PAE on the power amplifier integrated antenna by operating as shorting load on harmonics.

Dermatomyositis (DM) is an idiopathic inflammatory myopathy, characterized by inflammation of the proximal skeletal muscles and typical skin manifestations, which results in symmetric muscle weakness. A 43year-old man was presented with skin rash and left leg weakness, and he had a history of poliomyelitis. Initially, he was diagnosed as having post-polio syndrome (PPS) due to unilateral muscle weakness and a result of an the electromyography (EMG), which had shown patterns of PPS. After 4 months with conservative therapy for PPS, weakness of bilateral upper arms had developed and skin rashes on his entire body had aggravated and progressed. He was diagnosed as having dermatomyositis, based on elevated muscle enzyme levels, typical skin rashes, and typical EMG findings, which indicated muscle disease. When a patient with previous poliomyelitis has a newly developed muscle weakness or pain, we should consider various possible causes other than PPS.

A dual feeding active integrated antenna with high isolation between the Tx and Rx ports of a single triangular patch antenna is presented. The proposed antenna suppresses the third harmonics and isolates the Tx signal at the Rx ports to a high degree. The measured results of the return loss, isolation, and radiation patterns are provided.