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Korean Abstract: 이 연구는 유가가 미국 물가연동국채의 손익분기인플레이션(BEI)에 미치는 영향을 실증적으로 분석하였다. 추정결과 유가의 변동이 2년·5년· 10년 BEI에 통계적으로 유의한 영향을 미치는 것으로 나타났으며, 유가 변동이 BEI에 미치는 영향력은 물가연동국채의 만기가 짧을수록 더 높았다. 이 분석결과는 기대인플레이션이 장기적으로는 통화정책의 물가안정목표에 수렴하므로 유가의 변동은 단기적으로는 기대인플레이션에 유의한 영향을 줄 수 있으나 시간이 지나면서 그 영향력이 소멸하는 속성을 갖는다는 점을 보여준다. 특기할만한 점은 시장참가자들의 중장기 기대인플레이션의 대용치인 5Y5Y BEI가 유가가 하락하고 유가 선물곡선의 기울기도 하락하는 경우에만 유가 변동에 영향을 받는다는 점이다. 이 사실은 유가와 유가 선물곡선이 동시에 하락하는 경우에만 시장참가자들이 확신을 갖고 중장기 기대인플레이션(5Y5Y BEI)을 수정한다는 것으로 해석할 수 있다. BEI가 금융시장 참가자들의 기대인플레이션이라고 간주할 경우, 이 연구를 통해 유가가 시장참가자들의 기대인플레이션에 유의한 영향을 미친다는 점을 확인할 수 있었다. 나아가 유가의 변화에 더해 미래의 유가 경로도 시장참가자들의 중장기 기대인플레이션 형성에도 기여한다고 추론할 수 있다. English Abstract: This article is an empirical study on the effect of changes in oil prices on break-even inflation rates (BEIs) of Treasury Inflation Protected Securities (TIPS) of the United States. The results of this analysis show that oil prices make a statistically significant effect on the BEIs with maturities of 2 year, 5 year, and 10 year. These sensitivities are salient in the BEIs with shorter maturities. These implies that the changes in oil prices can affect inflation expectations in the short term but this effect gets diminished to the extinction because inflation expectations depend on the inflation target of a monetary policy. Notably, the 5Y5Y BEI has a statistically significant relation with the changes in oil prices only when the slope of oil futures curve flattens and oil prices are falling. This observation reveals that financial market participants adjust their inflation expectations with confidence only in case of the simultaneous drop of the slope of oil futures curve and oil prices. Assuming the BEI is a reasonable estimator of inflation expectations extracted from financial market, oil prices make a limited impact on medium and long term inflation expectations (5Y5Y BEI). From these results we can make an inference that current movements of oil prices and financial market participants’expectation of oil price path make joint contribution to the formation of medium and long term inflation expectations.

This paper proposes a constrained two-layer compression technique for electrocardiogram (ECG) waves, of which encoded parameters can be directly used for the diagnosis of arrhythmia. In the first layer, a single ECG beat is represented by one of the registered templates in the codebook. Since the required coding parameter in this layer is only the codebook index of the selected template, its compression ratio (CR) is very high. Note that the distribution of registered templates is also related to the characteristics of ECG waves, thus it can be used as a metric to detect various types of arrhythmias. The residual error between the input and the selected template is encoded by a wavelet-based transform coding in the second layer. The number of wavelet coefficients is constrained by pre-defined maximum distortion to be allowed. The MIT-BIH arrhythmia database is used to evaluate the performance of the proposed algorithm. The proposed algorithm shows around 7.18 CR when the reference value of percentage root mean square difference (PRD) is set to ten.

Atherosclerosis is a leading cause of cardiovascular disease. The early diagnosis of atherosclerosis is of clinical interest since it can prevent any adverse effects of atherosclerotic vascular diseases. In this paper, a new carotid artery radial strain estimation method based on autocorrelation is presented. In the proposed method, the strain is first estimated by the autocorrelation of two complex signals from the consecutive frames. Then, the angular phase from autocorrelation is converted to strain and strain rate and they are analyzed over time. In addition, a 2D strain image over region of interest in a carotid artery can be displayed. To evaluate the feasibility of the proposed radial strain estimation method, radiofrequency (RF) data of 408 frames in the carotid artery of a volunteer were acquired by a commercial ultrasound system equipped with a research package (V10, Samsung Medison, Korea) by using a L5-13IS linear array transducer. From in vivo carotid artery data, the mean strain estimate was -0.1372 while its minimum and maximum values were -2.961 and 0.909, respectively. Moreover, the overall strain estimates are highly correlated with the reconstructed M-mode trace. Similar results were obtained from the estimation of the strain rate change over time. These results indicate that the proposed carotid artery radial strain estimation method is useful for assessing the arterial wall’s stiffness noninvasively without increasing the computational complexity.

In ultrasound color Doppler imaging(CDI), effective clutter rejection is essential for estimating flow velocity and power. Since the clutter has time-varying characteristics, it is challenging to suppress it with a static clutter filter. In this paper, a new adaptive clutter rejection method based on spectral decomposition and tissue acceleration (ACR) for suppressing nonstationary clutter is presented. In the proposed method, tissue and flow characteristics are analyzed from singular value decomposition of backscattered Doppler signals to select optimal clutter filter from a bank of clutter filters. To evaluate the ACR method, phantom and in vivo experiments were conducted. For the phantom experiments, 20 frames of complex baseband data were acquired with a commercial ultrasound system (V10, Samsung Medison, Seoul, Korea) using a 3.5-MHz convex array probe by tapping over the flow phantom (Gammex 1425A LE, Gammex, Middleton, WI, USA) surface to mimic tissue movements. Similarly, 20 frames of in vivo liver data from a volunteer were also acquired. The performance of the proposed ACR method was compared with conventional clutter rejection methods, i.e., static (ST) and down-mixing (DM), using a commonly-used flow signal-to-clutter ratio (SCR) and fractional residual clutter area (FRCA). From the phantom experiments, the ACR method provided 2.03 dB and 0.98 dB improvements in SCR over the ST and DM methods. Similarly, ACR showed improvements in fractional residual clutter area (FRCA) compared to the ST and DM methods (i.e., 2.3% vs. 5.4 % and 3.7%, respectively). The consistent results were obtained with the in vivo experiments. The improvement in SCR from the ACR method is 4.90 dB and 3.98 dB, compared to the ST and DM methods. In addition, the ACR method showed less than 1% FRCA values for all 20 frames of in vivo data. These results indicate that the proposed ACR based on spectral decomposition and tissue acceleration can improve image quality in ultrasound color Doppler imaging by effectively removing the clutter.

Ultrasound color Doppler imaging has been a useful technique for obtaining vascular blood flow information. The conventional method, however, suffers from angle dependency when the blood flow is normal to the ultrasound beam direction so that it is difficult to visualize the blood flow. To overcome this angle dependency, various vector Doppler imaging methods with multiple transmit and receive sub-apertures have been proposed and showed an angle independent vessel flow information. However, most of them are evaluated on a linear array transducer. This paper evaluates a vector Doppler algorithm consisting of one transmit (TX) sub-aperture and two receive (RX) sub-apertures based on the convex and phased array transducer. Vessel flow velocity magnitudes and directions obtained by the vector Doppler using the convex and phased array show, for convex transducer mean direction error of 8.6843 degrees and 0.3860 m/s of mean velocity magnitude error and for phased array 16.1693 degrees and 0.0247 m/s mean errors respectively. These result indicate that convex and phased array also provide an reasonable vessel velocity magnitude and flow direction comparing to the vessel information of linear transducer which are errors of 2.9440 degrees and 0.1710 m/s respectively.

In conventional direction of arrival (DOA) estimation techniques, the inter-sensor spacing of an array is designed according to the minimal wavelength of an applied signal to avoid spatial ambiguity. This constraint greatly restricts the resolution of array or the performance of DOA estimation for a wide band signal. In this work, a new concept of wideband DOA estimation is described. Compared with multiple signal classification (MUSIC) method, the proposed method in this work uses multiple frequency bins instead of multiple sensors to form the steering vector, which reduces the sensor number for DOA estimation into 2. Besides, in this wideband DOA estimation method, the inter-sensor spacing is determined by the frequency resolution rather than the highest frequency (or minimal wavelength), so this method greatly decreases the restriction on sensor interval. Simulation results show that the proposed method with only two sensors can achieve comparative performance with convtmtional DOA estimation method using more than 20 sensors.

We report a case of in which the separation of a spinal needle shaft from a hub during subarachnoid block required surgical removal of the retained shaft. A 26-year-old male was scheduled for a transurethral resection of a bladder tumor under spinal anesthesia. A 25-gauge Quincke needle was selected. The needle was advanced to the junction of the hub and the L3-4 interspace through a midline approach, but the subarachnoid space was not identified. When the needle was withdrawn to change of direction of needle tip, the needle shaft separated from the hub. The separated needle shaft was palpable under the patient's skin, but it's removal using a Kelly through a small incision was impossible. Under the radiographic guidance, the needle was removed after several attempts. We emphasize importance of checking epuipment prior to a subarachnoid block and the use of a careful procedure to reduce complications associated with a faulty spinal needle.