Earticle

Background: Considering the kinetic chain of the lower extremity, a pronated foot position (PFP) can affect malalignment of the lower extremity, such as a dynamic knee valgus (DKV). Although the DKV during several single-leg movement tests has been investigated, no studies have compared the differences in DKV during a single-leg step down (SLSD) between subjects with and without PFP. Objects: The purpose of this study was to compare the DKV during SLSD between subjects with and without PFP. Methods: Twelve subjects with PFP (9 men, 3 women) and 15 subjects without PFP (12 men, 3 women) participated in this study. To calculate the DKV, frontal plane projection angle (FPPA), knee-in distance (KID), and hip-out distance (HOD) during SLSD were analyzed by two-dimensional video analysis software (Kinovea). Results: The FPPA was significantly lower in PFP group, compared with control group (166.4° ± 7.5° and 174.5° ± 5.5°, p < 0.05). Also, the KID was significantly greater in PFP group, compared with control group (12.7 ± 3.9 cm and 7.3 ± 2.4 cm, p < 0.05). However, the HOD not significantly differed between two groups (12.7 ± 1.7 cm and 11.4 ± 2.5 cm, p > 0.05). Conclusion: The PFP is associated with lower FPPA and greater KID. When assess the DKV during SLSD, the PFP should be considered as a crucial factor for occurrence of DKV.

Background: The lateral step down (LSD) is a form of stair negotiation used by the elderly because it requires less movement of the lower extremity. Although it is necessary to study the amount of pelvic drop and the strength of a hip abductor during LSD for intervention, limited studies have investigated the relationship between the amount of pelvic drop and strength of a hip abductor during LSD in elderly people. Objects: This study aimed to determine the relationship between the amount of pelvic drop on an unsupported leg and the strength of the hip abductor during LSD in the elderly. Methods: Thirty elderly people (male: 17, female: 13) were recruited. Subjects performed the LSD task, and the evaluator measured and the amount of pelvic drop on an unsupported side. Also, the isometric strength of the hip abductor was measured in a supine position. Results: We found significant relationships between the strength of the hip abductor and the amount of pelvic drop (r = -0.386). The average hip abductor strength normalized by body weight was 1.06 N/kg (max: 1.99, min: 0.52) and the average contralateral pelvic drop (CPD) angle was 4.16° (max: 15.3, min: 0). Conclusion: Our results indicated that the strength of the hip abductor had a moderate correlation with the CPD during a LSD in the elderly. Hip abductor weakness could translate into altered movement of the pelvis.

Relative contributions of lower extremity joints on the support moment were investigated in this study. Three-dimensional gait analyses were performed in normal walking and in unexpected step-down walking. For both gait studies, inverse dynamics were performed to obtain each joint moment of the lower extremity, which was applied to the forward dynamics simulation to determine the contributions on the support moment at different phases of walking. The forward dynamic simulation results showed that, in normal walking, the ankle plantar flexors contributed significantly during single-limb-support. However, the ankle plantar flexors, knee extensors and hip extensors worked together during double-limb-support. In unexpected step-down walking, the important contributors on the support of the body during single-limb-support were not only ankle plantar flexors but also knee extensors. This study, analyzing the relative contributions of the lower limb joint moments for the body support, would be helpful to understand different unexpected walking conditions and compensatory mechanisms for various pathological gaits.

PURPOSE: This study was conducted to investigate the most effective foot width for activating the lower extremity muscles during the lateral step-up and step-down motion according to three different foot positions. METHODS: In this single-blinded comparative study, a total of 28 adults performed the lateral step-up and step-down motion with feet positioned at 100% of shoulder width, 75% of shoulder width, and 50% of shoulder width. Surface electromyography (EMG) data were collected from the gluteus maximus (Gmax), gluteus medius (Gmed), vastus lateralis (VL), vastus medialis (VM), and biceps femoris (BF). RESULTS: The Gmax, Gmed, VL, VM and BF showed statistically significant differences according to the three feet positions (p < .05). When the feet were positioned at 100% of the shoulder width during the lateral step-up motion, all the muscle activities were greater than when the feet were positioned at 50% of the shoulder width (Gmax, +8%, p < .05; Gmed, +23.1%, p < .05; VL, +14%, p = .05; VM, +16%, p < .05; BF, +9.4%, p < .05). When the feet were positioned at 100% of the shoulder width during the lateral step- down motion, the muscle activity of Gmax, Gmed, VL, and VM was greater than when the feet were positioned at 50% of the shoulder width (Gmax, +9.4%, p < .05; Gmed, +9.5%, p < .05; VL, +16.1%, p < .05; VM, +11.3%, p < .05). CONCLUSION: During the lateral step-up and step-down motion, keeping the width between the feet the same as the shoulder width might be the most effective for activating the muscles of the lower extremity.

Background: This study was designed to investigate the correlation between electromyography (EMG) activities in the vastus medialis oblique (VMO) vs vastus lateralis (VL) activity ratio and the valgus collapse knee position while stepping down. Methods: Twenty healthy women volunteered to participate in this study. We measured the frontal-plane projections of the knee valgus angle, knee valgus distance, and hip adduction angle by using a digital camcorder. After 3 repetitions of the step down (dominant side) exercise, the findings of the static and dynamic phases were analyzed. EMG activities data of the VMO:VL activity ratio were recorded during the step down exercise and were normalized to the maximal voluntary isometric contraction (MVIC) of the quadriceps. A paired t-test was used to compare the findings of the static and dynamic phases. We analyzed the Spearman’s rank order correlation coefficient between the and VMO:VL ratio. Results: Hip adduction angle, knee valgus angle, VMO activity, VL activity, VMO:VL activity ratio were statistically higher in the dynamic phase than in the static phase (p<.05). Frontal-plane projections of knee valgus angle were significantly correlated with hip adduction angle (r=.459, p<.05) and knee valgus distance (r=.505, p<.05). However, the EMG activity ratio of the VMO and the VL did not show a significant change during step down exercise with respect to hip adduction angle (p=.875), knee valgus angle (p=.618), and knee valgus distance (p=.701). Conclusion: The results from this study indicate that frontal-plane projections of knee valgus angle were associated with hip adduction angle and knee valgus distance. On the basis of these results, the knee valgus distance may be used to determine the valgus collapse knee position while stepping down.

In this paper, a review of the common techniques used for high step-down dc-dc voltage conversion is presented. First, the limitations of conventional buck & synchronous rectifier buck converters used for high step down dc-dc voltage conversion which include narrow duty cycle, high voltage stress, large ripple and low efficiency are briefly discussed. Then various topologies of non-isolated step-down dc-dc converters are reviewed and discussed. The topologies/techniques used for high step down dc-dc conversion are divided into various groups which include interleaved, quadratic, tapped, switched capacitor, switched inductor, coupled inductor, multi level and buck converter with three state switching cells. Each group of converters is briefly discussed, main circuit structure of each topology is given and their features and limitations are given. Finally a comparison of all the discussed topologies is carried out based on some common features.

본 논문에서는 step down 구조인 ELS(Equity Linked Security) 상품의 리스크량이 발행 수익을 인식하는 방법에 따라 어떻게 변화할 수 있는지 알아보도록 한다. 일반적으로 통용되는 이연수익과 이론가를 이원적 관리하는 분리 이연수익 인식(DDRR, Divided Deferred Revenue Recognition) 방식을 설명하고, 이연수익을 이론가 자체에서 고려하여 조기상환 구조에 보다 적합하다고 판단되는 내재 이연수익 인식(IDRR, Implied Deferred Revenue Recognition) 방식을 소개하도록 한다. DDRR의 경우는 ELS 헷지 거래를 위한 그릭 포지션이 이연수익과는 별개로 계산되므로 보다 큰 레버리지 효과를 만들어 내게 되며, 이에 따라 pin risk 상황과 같이 조기상환 여부가 불확실할 때 북운용의 안정성을 저해하게 된다. 반면 IDRR의 경우는 이연수익이 이론가 평가 내에 고려되어 그릭스 절대값 축소되는 디레버리지 효과가 있고, pin risk에서도 상대적으로 안정적인 운용이 가능함을 확인할 수 있다.

In this paper, we compares risk amount (such as stability of mark to market, explaining power of the greeks, and delta profile near the pin risk) of the step down product, the most famous ELS(Equity Linked Security), generated from the different approach on how to recognize the deferred profit. The traditional DDRR, Divided Deferred Revenue Recognition, which separates the theoretical value and revenue from issuing, is reviewed, and IDRR, Implied Deferred Revenue Recognition, which inserts revenue from issuing as the input of theoretical value, are introduced. The DDRR leads to higher leverage since this value is constructed without considering revenue recognition at early termination. Thus the stability at pin risk area is deteriorated. In contrary, IDRR can enhance greeks stability, and construct less leveraged and robust hedge position especially at pin risk, as theoretical valuation includes the effect of revenue recognition at early termination.

본 연구는 주가연계증권, 특히 Step-down형 2 Stock ELS의 일별 가치를 평가하고, 이를 이용한 수익성 및 위험 분석을 통하여 옵션부 증권의 특성과 유용성을 평가하고자 하였다. 2006년 5월부터 11월 사이에 국내 증권회사에서 발행한 ELS 중 30개를 대상으로 몬테카를로 시뮬레이션을 이용하여 일별로 가치를 평가한다. 이를 이용하여 일별 기대 수익률 및 Downside Risk를 측정하고, KOSPI200 지수와 비교하여 ELS의 수익성 및 위험에 대한 평가를 한다. 또한 분석 대상 30개 상품 중 10개에 대하여 과거의 시장 상황(2000년 1월 기준)을 가정하여 수익성 및 위험을 재평가 한다. 분석 결과 발행 시점을 기준으로 한 경우와 과거 시점(2000년 1월)을 기준으로 한 경우, 평균 수익률은 양쪽 모두 KOSPI200 지수에 비해 높게 나타났지만, 위험도 높게 나타났다. 한편, 조기상환이 빠르게 이루어질수록 위험이 낮았다. 이상의 결과를 종합해 볼 때, KOSPI200과 비교한 ELS는 전체적으로 수익의 측면에서는 양호한 성과를 보이지만, 일반적으로 인식하고 있는 위험보다 높은 위험이 있는 상품이라고 할 수 있다. 특히, ELS는 만기가 확정되어 있어 시장 상황 악화 시 손절매에 따른 비용이 추가로 발생한다. 이는 투자자의 의사결정이 제약을 받게 되어 위험이 직접 투자 또는 펀드와 같은 일반적인 간접 투자 상품보다 가중됨을 의미한다.

This study investigates the daily valuation and risk of step-down two-stock ELS. The 30 ELS products issued by domestic securities companies between May 2006 and November 2006 are examined. From the daily valuation using Monte Carlo simulation and downside risk analysis, this study compares the risk and return of step-down 2 stock ELS with those of KOSPI200. To further study the effect of bearish market on the findings, 10 out of 30 are re-analyzed with the assumption that they are issued under the same conditions in January 2000. Both analyses reveal that the expected return and downside risk of step-down ELS is higher than those of KOSPI200. And as the time early redemption is getting closer, the downside risk of ELS is getting lower. Our findings are different from the common sense that the return of ELS product is higher than market portfolio, but its risk is lower.

In this paper, a passive damping network between two stages of a cascaded DC-DC boost/buck interleaved converter was proposed to enhance the dynamic behavior. By this damping network, the right-half plane zeros in converter's transfer function are sufficiently departed from the left half-plane, which leads to more damped transient behavior. A frequency analysis illustrated the dynamic enhancement in the proposed converter. To validate the theoretical model under different related circumstances, experimental results are presented through implementing a prototype setup.

Piezoelectric transformers(PT) are expected to be small, thin and highly efficient, and which are attractive as a transformer with high power density for step down voltage. For these reasons, we have attempted to develop a step-down PT for the miniaturized adaptor. We propose a PT, operating in thickness extensional vibration mode for step-down voltage. This PT consists of a multi-layered construction in the thickness direction. In order to develop the step-down PT of 10 W class and turn ratio of 0.1 with high efficiency and miniaturization, the piezoelectric ceramics and PT designs are estimated with a variety of characteristics. The basic composition of piezoelectric ceramics consists of ternary yPb(Zr$_{x}$Ti$_{1-x}$)O$_{3}$-(1-y)Pb(Mn$_{1/3}$Nb1$_{1/3}$Sb$_{1/3}$)O$_{3}$. In the piezoelectric characteristics evaluations, at y=0.95 and x=0.505, the electromechanical coupling factor(K$_{p}$) is 58$\%$, piezoelectric strain constant(d$_{33}$) is 270 pC/N, mechanical quality factor(Qr$_{m}$) is 1520, permittivity($\varepsilon$/ 0) is 1500, and Curie temperature is 350 $^{\circ}C$. At y = 0.90 and x = 0.500, kp is 56$\%$, d33 is 250 pC/N, Q$_{m}$ is 1820, $\varepsilon$$_{33}$$^{T}$/$\varepsilon$$_{0}$ is 1120, and Curie temperature is 290 $^{\circ}C$. It shows the excellent properties at morphotropic phase boundary regions. PZT-PMNS ceramic may be available for high power piezoelectric devices such as PTs. The design of step-down PTs for adaptor proposes a multi-layer structure to overcome some structural defects of conventional PTs. In order to design PTs and analyze their performances, the finite element analysis and equivalent circuit analysis method are applied. The maximum peak of gain G as a first mode for thickness extensional vibration occurs near 0.85 MHz at load resistance of 10 .The peak of second mode at 1.7 MHz is 0.12 and the efficiency is 92$\%$.

This study was performed to investigate the effect of root canal shaping techniques on the change of the shape of prepared root canal. 40 mesiobuccal canals of recently extracted mandibular 1st and 2nd molars were divided into 4 groups and shaped by step-down/balanced force technique, step-down/step-back technique, step-back technique and conventional technique respectively. The change of the shape of root canal was traced by superimposing the radiographs obtained before and after shaping of each root canal. The results were as follows. 1. By the experimented techniques except conventional technique, the root canals were more shaped in convex side of apical area and in concave side of most curved and coronal area than in the other sides(P<0.05). By conventional technique, the root canals were more shaped in convex side than in convave side from apex to orifice(P<0.05). 2. By step-down/balanced force technique, the cancave sides at C and D points of proximal view and C point of clinical view were more shaped than the convex side(P<0.05). Through the entire canal, the concave side was more shaped than the convex side in proximal view(P<0.01). But there was no statistical difference between both sides in clinical view. 3. By step-down/step-back technique, the change of root canal shape was not statistically different in concave and convex sides at each point of both views(P>0.05). And through the entire canal in proximal view, there was no statistical difference in shaping percentage between both sides. But through the entire canal in clinical view, the concave side was more shaped than the convex side(P<0.1). 4. By step-back technique, the convex side at B point of clinical more shaped than the other sides(P<0.05). Through the entire canal in proximal and clinical views, there was no statistical difference in shaping percentage between both sides. 5. Comparing the total shaping percentage among techniques, that in conventional technique was the greatest numerically, and followed by the percentages in step-down/step-back, step-down/balanced force and step-back technique. But, in proximal view, shaping percentages were not statistically different among techniques(P>0.05, ANOVA test). In clinical view, shaping percentages in step-back and conventional techniques were statistically different(P<0.01, ANOVA test). * Proximal view: radiograph taken in mesiodistal direction. * Clincal view: radiograph taken in faciolingual direction. A point : 1mm point from radiographic apex B point : center point between A and C points C point : most curved point of root canal D point : center point between C point and canal oriffice.

This paper describes a step-down AC voltage regulator using an AC chopper and auxiliary transformer, which is a series connected to the main input. The detail design of the AC regulator, logic and PWM pattern of the AC chopper is described and the three-phase AC regulator using two single­phase AC choppers with a three transformer configuration is proposed for three-phase application. The proposed three-phase system has the advantages of lower system cost due to reduced switch number and gate driver circuit as well as advantages of decreased size and weight because it uses a series compensated scheme. The proposed AC regulator has many benefits such as fast voltage control, high efficiency and simple control logic. Experimental results indicate that it can be used as a step-down AC voltage regulator for power saving purposes very efficiently.

This paper shows a new methodology for evaluating the value and sensitivity of autocall knock-in type equity-linked securities. While the existing evaluation methods, Monte Carlo simulation and finite difference method, have limitations in underestimating the knock-in effect, which is one of the important characteristics of this type, this paper presents a precise joint probability formula for multiple autocall chances and knock-in events. Based on this, the calculation results obtained by utilizing numerical and Monte Carlo integration are presented and compared with those of existing models. The results of the proposed model show notable improvements in terms of accuracy and calculation time.

High voltage step-down converters are very popular in distributed power systems, voltage regular modules, automatic vehicles, etc. To avoid extreme duty cycles, a series capacitor-based buck converter with a coupled inductor is proposed in this paper. In this converter, the voltage stresses of the power switches are clamped to half of the input voltage. Thus, low voltage rating MOSFETs with a low R_ds,on could be utilized to improve the performance of the proposed converter. Moreover, synchronous MOSFETs are also used to reduce the conduction losses of the switches. Zero voltage switching (ZVS) for the main power switches is achieved using the coupled-inductor technique. In addition, through adding a bypass flowing path, a negative current is established to guarantee the ZVS condition of the power switches. The operating principle of the proposed converter is described in this paper, and the DC voltage gain ratio, automatic current sharing, soft switching condition and design guideline of the critical parameters are also given. Finally, experimental results obtained from a 60 V/200 W prototype are presented to verify the analysis of the proposed converter.

The globalization of financial markets has broadened investment opportunities. International investors' investment portfolios consist of financial instruments from various countries; consequently, the risks associated with economic dependence among countries should be carefully considered. Step-down equity-linked securities (ELS) are a structured financial product that have recently become popular among Korean investors. Payoffs are based on two or three stock indices from different regions; therefore, dependence between the indices should be reflected in the risk analysis. In this study, we consider a regime-switching copula model to describe the joint behavior of two stock indices- the Eurostoxx50 and the Hang Seng China Enterprises Index (HSCEI). These indices are commonly used as underlying assets of step-down ELS. Using historical data, we analyze the risk associated with step-down ELS through the probabilities of early redemption. A regime-switching copula model can accommodate complicated dependence. Thus, it should be considered in the risk analysis of step-down ELS.

This paper is an empirical study of timing rules in the change of chief executive officers (CEO, or shacho in Japanese) in large Japanese firms. Organizational rules on CEO’s tenure provide an important mechanism for limiting the power of CEO. By identifying three types of tenure rules?unit term rule, tenure limit rule, and retirement age rule, I discuss the enabling role of tenure rules in CEO change process. In addition, I suggest tenure milestone set by predecessor’s tenure as a key concept in understanding the role of tenure rules in CEO change process. A CEO’s life cycle could be divided into three distinctive periods based on tenure milestone?before the milestone, milestone, and over-the milestone?presenting different mandates for the incumbent CEO. Specifically, I hypothesize that (1) CEO succession is more likely during the tenure milestone period; (2) the effect of performance is different across three periods; and (3) organizational and political factors moderates the tenure milestone effect on CEO change. I test the hypotheses in the sample of 200 largest industrial companies in Japan over the period of 1955-1995 using the event history analysis. The empirical results show that hazard rate is higher during the tenure milestone period and that the negative effect of performance is stronger in the over-the-milestone period than in the other two periods. Finally, organizational and political factors, such as the existence of large internal talent pool and the subunit rivalry resulting from merger, also facilitate CEO change during the tenure milestone period.

The voltage gain of a traditional buck converter is finite due to the high voltage across the semiconductor and reduced efficiency. A non-isolated high step-down DC.DC converter based on symmetric switched inductors is proposed in this paper. The connection of inductors in series or in parallel is controlled by switches to improve the conversion ratio. The converter has many beneficial characteristics, such as high step-down, reduced voltage stresses, and high efficiency. Moreover, it can realize voltage balance on the switches. The voltage on the switch does not oscillate and the loss of the switches is reduced. Therefore, the efficiency of the whole topology is improved. This paper discusses the operation principle, modes analysis, voltage gain analysis, voltage stress analysis, output ripple analysis, loss analysis, comparative analysis and design considerations. The correctness of the theoretical analysis of the proposed converter is verified by a laboratory prototype, and its peak efficiency reaches 96.5%.

We study the pricing of reverse step-down equity-linked securities by means of an implicit finite difference method applied to the Black-Scholes partial differential equation. In the classical step-down structure, early redemption is triggered when the underlying asset price rises above a fixed level. Unlike this structure, the reverse variant redeems early when the price falls below a prescribed threshold. This inversion of the redemption condition places the capital-loss zone on the upside. The structure is therefore attractive to investors who anticipate a decline in the underlying asset. We formulate the governing equation and boundary conditions for both structures. We then discretise them on a uniform spatial grid and solve the resulting tridiagonal systems by the Thomas algorithm at each backward time step. The method is applied to three market instruments (the KOSPI200 index, SK Hynix stock, and Tesla stock) with volatilities obtained from reported market data. We also carry out a systematic spatial grid convergence study for the KOSPI200 reverse product. The study shows that the computed price converges monotonically to a stable reference value as the grid spacing decreases. The empirical convergence rates are presented at each refinement level. The grid spacing is chosen to make all barrier and strike levels coincide with grid nodes at every refinement level. For the grid sequence considered, this alignment yields a monotone error sequence and avoids the oscillations that misaligned grids can produce. We further report a temporal convergence study, a sensitivity analysis of the price to the truncation boundary and to the reverse knock-in barrier, and an independent Monte Carlo validation of the computed prices.

In this study, the design of low voltage DC-DC converter with low triggering ESD (Electro-Static Discharge) protection circuit was investigated. The purpose of this paper is design optimization for low voltage(2.5V to 5.5V input range) DC-DC converter using CMOS switch. In CMOS switch environment, a dominant loss component is not switching loss but conduction loss at 1.2MHz switching frequency. In this study a constant frequency PWM converter with synchronous rectifier is used. And zener Triggered SCR device to protect the ESD phenomenon was designed. This structure reduces the trigger voltage by making the zener junction between the lateral PNP and base of lateral NPN in SCR structure. The triggering voltage was simulated to 8V.