Showing papers by "Hanyang University published in 1996"

Observability of target tracking with bearings-only measurements

Abstract: Observability requirements are obtained for three-dimensional maneuvering target tracking with bearings-only measurements. The approach taken here using pseudomeasurements is completely different from the previous work in this area in that it does not involve solutions of nonlinear differential equations resulting from complicated time differentiations and it can treat a more general class of target motions not restricted to N th-order target dynamics.

Structure and Nonlinear Optical Properties of Sb2O3-B2O3 Binary Glasses

Abstract: The third order nonlinear optical susceptibilities χ(3) of Sb2O3-B2O3 binary glasses have been measured by the third harmonic generation (THG) method. The IR and Raman spectroscopic study reconfirmed that the structure of Sb2O3 glass is similar not to senarmontite but to valentinite which consists of double-chains of SbO3 units. The formation of BO4 units is much smaller for Sb2O3-B2O3 glasses than Bi2O3-B2O3 glasses at all compositions, which is ascribed to the covalent character of Sb-O bonds. It is also considered that Sb2O3 is present as SbO3 trigonal units and participates in the glass network formation through the Sb-O-B bonds. The χ(3) value increased monotonically with increasing Sb2O3 content up to 8.4×10-13 esu for Sb2O3 glass, which is about 30 times larger than SiO2 glass. Modified Lines'linear relationship between χ(3) and (nω2+2)3·(nω2-1)·Ed/E02 was adopted to Sb2O3-B2O3 glasses.

Synthesis and swelling characteristics of pH and thermoresponsive interpenetrating polymer network hydrogel composed of poly(vinyl alcohol) and poly(acrylic acid)

Abstract: The swelling behavior of novel pH- and temperature-sensitive interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) in water was investigated. The PVA/PAAc IPN hydrogels were synthesized by UV irradiation, followed by a repetitive freezing and thawing process by which PVA hydrogel networks were formed inside of cross-linked PAAc chains. The swelling behaviors of these IPNs were analyzed in buffer solution at various pH and temperature ranges. Swelling ratios of all IPNs were relatively high, and they showed reasonable sensitivity to both pH and temperature. Hydrogels showed both the positive and negative swelling behaviors depending on PAAc content. IPN46 showed the positive temperature-sensitive swelling behaviors and its stepwise changes in swelling ratio was about 1.8 and 2.0 obtained between 25 and 45°C at pH 7, and between pH 4 and 7 at 35°C, respectively. The positive temperature dependence is attributed to the formation and dissociation of hydrogen bonding complexes between PVA and PAAc. These IPNs are expected to show a pH- and temperature-sensitive drug release according to the stepwise behavior at this temperature region. © 1996 John Wiley & Sons, Inc.

Dietary Zinc Deficiency Alters 5α-Reduction and Aromatization of Testosterone and Androgen and Estrogen Receptors in Rat Liver

Abstract: We studied the effects of zinc deficiency on hepatic androgen metabolism and aromatization, androgen and estrogen receptor binding, and circulating levels of reproductive hormones in freely fed, pair-fed and zinc deficient rats. Hepatic conversion of testosterone to dihydrotestosterone was significantly less, but formation of estradiol from testosterone was significantly greater in rats fed the zinc-deficient diet compared with freely fed and pair-fed control rats. There were significantly lower serum concentrations of luteinizing hormone, estradiol and testosterone in rats fed the zinc-deficient diet. No difference in the concentration of serum follicle-stimulating hormone was observed between the zinc-deficient group and either control group. Scatchard analyses of the receptor binding data showed a significantly higher level of estrogen receptor in zinc-deficient rats (36.6 +/- 3.4 fmol/mg protein) than in pair-fed controls (23.3 +/- 2.2 fmol/mg protein) and a significantly lower level of androgen binding sites in rats fed the zinc-deficient diet (6.7 +/- 0.7 fmol/mg protein) than in pair-fed control rats (11.3 +/- 1.2 fmol/mg protein). There were no differences in hepatic androgen and estrogen receptor levels between freely fed and pair-fed controls. These findings indicate that zinc deficiency reduces circulating luteinizing hormone and testosterone concentrations, alters hepatic steroid metabolism, and modifies sex steroid hormone receptor levels, thereby contributing to the pathogenesis of male reproductive dysfunction.

Practical guidance for homing missiles with bearings-only measurements

Abstract: Observability is analyzed for the target tracking with bearings-only measurements (BOM) applied to a passive homing missile system using augmented proportional navigation guidance (APNG). Based on the analysis, a practical homing guidance law is proposed to enhance observability for tactical missile applications. The new guidance law is tailored to provide oscillation of line-of-sight (LOS) angle induced by initial missile heading errors without sacrificing terminal effectiveness. Simulation studies indicate that the proposed guidance law provides convergence of the state estimates essential to homing guidance applications as well as terminal effectiveness.

Torque and unbalanced magnetic force in a rotational unsymmetric brushless DC motors

Abstract: The pole-teeth-winding configuration in brushless dc motors determines torque and unbalanced magnetic force which are the resultants of the tangential and the normal magnetic force in a small air gap, respectively. This paper calculated torque and unbalanced magnetic force using FEM, Maxwell stress tensor to investigate the influence of pole-teeth-winding patterns on the performance from two common designs, i.e. the rotational symmetric 12-pole 9-tooth (12P9S) motor and the rotational unsymmetric 8-pole 9-tooth (8P9S) motor, and proposed the rotational unsymmetric 10-pole 9-tooth (10P9S) motor which achieves the high average torque of 12P9S motor and the low cogging torque of 8P9S at the same time. The analyses show that 8P9S and 10P9S motor tend to have less cogging torque because their bigger values of the least common multiple of pole and teeth reduce the cogging torque. The torque efficiency depends on pole-teeth-winding configuration. ABC-winding of 12P9S motor and three consecutive teeth winding of 10P9S motor utilize all six energized coil effectively to produce the high average torque. The normal magnetic force in a rotational unsymmetric design is not balanced and results in unbalanced magnetic force.

Preparation, characterization and properties of β-chitin and N-acetylated β-chitin

Abstract: Free amino groups in β-chitin from squid pen were acetylated to obtain N-acetylated β-chitin. After careful control of degree of acetylation, thermal and mechanical properties of β-chitin and N-acetylated β-chitin were compared. The structural differences of β-chitin and N-acetylated β-chitin were characterized by Fourier transform infrared (FTIR) and wide-angle x-ray diffraction (WAXD) analysis. The results indicated that the crystallinity of N-acetylated β-chitin was higher than that of β-chitin and N-acetylated β-chitin exhibited characteristics similar to α-chitin. Equilibrium water content (EWC) of β-chitin reached to about 50% and this hydrophilic nature was assumed to be caused by a relatively weak hydrogen bonding force of β-chitin with parallel main chains. On the other hand, EWC of N-acetylated β-chitin was 40% due to the introduction of ordered structure. β-chitin and N-acetylated β-chitin have the tensile strength of 0.4 and 0.7 Mpa in the swollen state, respectively. Viscoelastic properties and thermal relaxation behaviors were investigated by dynamic mechanical thermal analysis (DMTA). DMTA spectra of these samples showed that α-transition peaks of β-chitin and N-acetylated β-chitin were observed at 170 and 190°C, respectively. These relaxation peak maxima were assigned to be their glass transition temperature. In addition, a second relaxation peak of β-chitin resulting from acetamide groups was found at 112°C and a broad relaxation peak of N-acetylated β-chitin at around 81–100°C. As a result of thermogravimetric analysis, 10% weight loss temperatures of β-chitin and N-acetylated β-chitin were 270 and 285°C, respectively. © 1996 John Wiley & Sons, Inc.

Trace representation of Legendre sequences of Mersenne prime period

Abstract: In this correspondence, it is shown that Legendre sequences of period p can be explicitly represented using the trace function defined on the finite field with 2/sup n/ elements, whenever p=2/sup n/-1 is prime for some n/spl ges/3.

Combined effect of bicarbonate and insulin with glucose in acute therapy of hyperkalemia in end-stage renal disease patients.

Abstract: This study was performed to evaluate the efficacy of various treatment modalities for hyperkalemia in 8 end-stage renal disease (ESRD) patients. Simultaneous administration of sodium bicarbonate and i

Robust design for unconstrained optimization problems using the Taguchi method

Abstract: Engineering optimization has been developed for the economic design of engineering systems. The conventional optimum is determined without considering noise factors. Thus, applications to practical problems may be limited. Within current design practice, noises tend to be allowed for by specification of closer tolerances, or the use of safety factors. However, these approaches may be economically infeasible. Thus, the inclusion of design-variable noises is required for practical design in optimization. A method is developed to find robust solutions for unconstrained optimization problems. The method is applied to problems with discrete variables. The orthogonal array based on the Taguchi concept is utilized to arrange the discrete variables. Through several examples, it is verified that the solutions from the suggested method are more insensitive to noise than the conventional optimum within the range of variations for design variables.

Plasma surface graft of acrylic acid onto a porous poly(vinylidene fluoride) membrane and its riboflavin permeation

Abstract: Acrylic acid was grafted onto the surface of commercial poly(vinylidene fluoride) (PVDF) membrane using plasma polymerization techniques. Graft reaction was confirmed by X-ray photoelectron spectroscopy (XPS) spectra and attenuated total reflectance Fourier transform infrared spectra. Grafting rate was dependent on plasma exposure time. For argon plasma at 30 W, grafting rate decreased after maximum rate was observed at 30 s exposure. PVDF membrane with 30 s plasma exposure and subsequently grafted with acrylic acid (AA-3) showed the greatest O1s/F1s area ratio in XPS spectra. Thus its graft density and degree of polymerization were the largest among the graft membranes. Permeation of riboflavin through all poly(acrylic acid)-g-PVDF membranes showed a decrease in permeability of riboflavin in pH 4–5. © 1996 John Wiley & Sons, Inc.

Applications of Petri networks to transportation network modeling

Abstract: The development of a mathematical modular framework based on Petri network (PN) theory to model a traffic network is the subject of this paper. Traffic intersections are the primitive elements of a transportation network and are characterized as event-driven and asynchronous systems. Petri networks have been utilized to model these discrete event systems; further analysis of their structure can reveal information relevant to the concurrency, parallelism, synchronization, and deadlock avoidance issues. The Petri-net model of a generic traffic junction is presented, with its deadlock avoidance property proven. These modular networks are effective in synchronizing their components and can be used for modeling of an asynchronous large-scale transportation system. The derived model is suitable for simulations on a multiprocessor computer since its program execution safety is secured. The software pseudocode for simulating a transportation network model on a multiprocessor system is presented.

Preparation of barium titanate by homogeneous precipitation

Abstract: The barium titanyl oxalate, which was the precursor of barium titanate, was prepared by homogeneous precipitation using the diethyl oxalate as a precipitating agent. The oxalate dried at 80 °C was the crystalline phase, which was converted to amorphous-like phase after drying at 120 °C. The weight loss of oxalate was 47.3 wt%. The chemical formula of the oxalate could correspond to BaTiO(C2O4)2 · 4H2O. The barium titanate obtained from the calcination of oxalate at 850 °C was a tetragonal phase with a particle size of 0.2 μm.

Tax Advice and Reporting under Uncertainty: Theory and Experimental Evidence*

Abstract: . This study extends the Beck, Davis, and Jung (1992) experimental study by incorporating opportunities for taxpayer subjects to purchase advice before making their tax reporting decisions. Tax advice has two roles in the model and experiment. First, tax advice allows taxpayers to reduce their uncertainty about the amount of taxes owed. This permits us to study the demand for tax advice in conjunction with its effect on tax reporting decisions. Second, the decision to purchase tax advice from an expert provides a means of signaling that may alter tax agency audit policies. The resulting audit policies, in turn, can affect taxpayers' decisions to purchase tax advice. These interdependencies are incorporated in a game-theoretic model and several predictions are tested experimentally. Consistent with theory, subjects sorted themselves into three groups based upon their private information. Another prediction supported by the experiment is that the demand for tax advice increased with the magnitude of an uncertain tax deduction (amount-at-risk). We also found, as expected, that the effects of tax advice on pre-audit tax revenues depend upon the amount-at-risk. When the amount-at-risk was high, subjects in settings with tax advice reported lower average incomes and paid lower taxes than did those subjects in settings without the opportunity to purchase tax advice. The opposite was true for the low amount-at-risk condition, supporting our prediction that tax advice and amount-at-risk would have an interactive effect on tax reporting. Analysis was also performed on post-audit tax collections. Contrary to theory, post-audit tax payments were found to increase when subjects had an opportunity to purchase tax advice. This result apparently was caused by a tendency to over-purchase tax advice and, in some cases, to report a low income regardless of the advice received. Resume. Les auteurs developpent l'etude experimentale de Beck, Davis et Jung (1992) en y incorporant la possibilite pour les sujets contribuables de solliciter des conseils avant de prendre leurs decisions relatives a l'information qu'ils fourniront aux fins fiscales. Les conseils fiscaux jouent deux roles dans le modele et l'experience. Premierement, ils permettent aux contribuables de reduire leur incertitude relative au montant des impots auxquels ils sont assujettis. Les auteurs peuvent ainsi etudier la demande de conseils fiscaux en conjonction avec leurs consequences sur les decisions relatives a l'information a fournir aux fins fiscales. Deuxiemement, la decision de solliciter les conseils fiscaux d'un expert est un signal pouvant influer sur les politiques de verification des representants du fisc. A leur tour, ces politiques peuvent influer sur les decisions des contribuables de solliciter des conseils fiscaux. Ces interdependances ont ete integrees a un modele de jeu theorique et les auteurs ont verifie plusieurs predictions par experimentation. Conformement a la theorie, les sujets se sont repartis en trois groupes, en fonction de l'information privilegiee dont ils disposaient. L'experimentation a confirme une autre prediction: la demande de conseils fiscaux augmente avec l'importance de la somme dont la deductibilite est incertaine (montant a risque). Les auteurs constatent egalement, comme ils s'y attendaient, que les effets des conseils fiscaux sur les recettes fiscales anterieures a la verification dependent du montant a risque. Lorsque le montant a risque est eleve, les sujets pouvant solliciter des conseils fiscaux font etat de revenus moyens inferieurs et paient moins d'impot que les sujets n'ayant pas la possibilite de solliciter des conseils fiscaux. L'inverse est vrai lorsque le montant a risque est faible, ce qui confirme la prediction selon laquelle les conseils fiscaux et le montant a risque ont un effet interactif sur l'information fournie aux fins fiscales. Les auteurs analysent egalement les impots percus posterieurement a la verification. Contrairement a la theorie, ils constatent que les paiements fiscaux posterieurs a la verification augmentent lorsque les sujets ont eu la possibilite de solliciter des conseils fiscaux. Ce resultat semble etre attribuable a une tendance a solliciter des conseils fiscaux avec exces et, dans certains cas, a faire etat d'un faible revenu, malgre les conseils recus.

Regulation of smooth muscle delayed rectifier K+ channels by protein kinase A

Abstract: We identified voltage-activated K+ channels in freshly dispersed smooth muscle cells from the circular layer of the canine colon in patch-clamp experiments using 200 nM charybdotoxin to suppress 270-pS Ca2+-activated K+ channels (BK channels). Three channel types were distinguished in symmetrical 140 mM KCl solutions: 19.5 ± 1.7 pS channels (KDR1), 90.6 ± 5.4 pS channels (KDR2) and 149 ± 4 pS intermediate-conductance Ca2+-activated K+ channels (IK channels). All three types showed an increase in open probability with membrane depolarization. Ensemble average current from KDR1 channels inactivated with a time constant of 1.7 ± 0.1 s at +60 mV test potential, while KDR2 and IK channels did not show inactivation. IK channels were activated by free cytoplasmic [Ca2+] (10−6M) but were insensitive to 4-aminopyridine (4-AP, 10 mM) and intracellular tetraethylammonium (TEA, 1 mM). KDR1 channels were sensitive to 4-AP (10 mM) and intracellular TEA (1–10 mM) but not to Ca2+. KDR2 channels did not have a consistent pharmacological profile, suggesting that this class may be comprised of several subtypes. At +40 mV membrane potential, the catalytic subunit of protein kinase A (PKA) increased the open probability of KDR1 channels 3.4-fold and of KDR2 channels 3.9-fold, but had no effect on IK channels. In the absence of Mg-ATP, PKA did not affect channel open probabilities. At physiological membrane potentials (− 60 mV) only openings of KDR1 channels could be induced by PKA, suggesting that these 4-AP-sensitive 20-pS K+ channels are primarily responsible for the cAMP-mediated hyperpolarization of colonic smooth muscle cells.

Swelling of thermosensitive interpenetrating polymer networks composed of poly(vinyl alcohol) and poly(acrylic acid)

Abstract: The swelling behavior of interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) in water was studied. The PVA/PAA IPN gels were prepared by four synthetic methods. The swelling behaviors of these IPNs made by different methods were compared. The differences in swelling behaviors of samples are discussed on the basis of their structural and physical differences.

On the weight hierarchy of Kerdock codes over Z/sub 4/

Abstract: The rth generalized Hamming weight d/sub r/ of the Kerdock code of length 2/sup m/ over Z/sub 4/ is considered. A lower bound on d/sub r/ is derived for any r, and d/sub r/ is exactly determined for r=0.5, 1, 1.5, 2, 2.5. In the case of length 2/sup 2m/, d/sub r/ is determined for any r, where 0/spl les/r/spl les/m and 2r is an integer. In addition, it is shown that it is sometimes possible to determine the generalized Hamming weights of the Kerdock codes of larger length using the results of d/sub r/ for a given length. The authors also provide a closed-form expression for the Lee weight of a Kerdock codeword in terms of the coefficients in its trace expansion.

Collateral pathways in Budd-Chiari syndrome: CT and venographic correlation.

Abstract: B udd-Chiari syndrome (BCS) is a diverse group of conditions associated with obstruction of hepatic venous outflow at the level of the large hepatic vein or the extrahepatic segment of the inferior vena cava (IVC). BCS is classified as primary or secondary, depending on the cause and pathophysiologic manifestations. Although BCS in Western countries is most often due to thrombotic obstruction of the hepatic vein or IVC caused by systemic disease or malignant tumors, primary membranous or segmental obstruction of the IVC is the most common cause of BCS in Asian countries ( 1. 21. Because primary BCS is chronic. several pathways of collateral vessels commonly develop. Development of collateral circulation is contingent on the level of obstruction and the length of the obstructed segment. Collateral pathways of upper caval obstruction have not been as carefully studied as other areas; findings have mostly relied on venography. Although Cf scans are the most common primary method for evaluating abdominal abnormalities, several CT studies of BCS have dealt largely with changes in liver parenchyma. With knowledge of vascular anatomy on abdominal CT, it is relatively easy to outline the collateral vessels because of their larger caliber due to vascular engorgement [3]. The purpose of this essay is to classify and illustrate the collateral pathways of BCS in abdominal CT scans. Left Renal-Hemiazygos Pathway Anatomically. the left renal vein is more complex than the right because of multiple vessels (the inferior phrenic. capsular. adrenal. and gonadal veins) that join the left renal vein. In addition, the left renal vein communicates with the retroperitoneal vein (by the lumbar. ascending lumbar, and hemiazygos veins) in two thirds of cases 141In fact, the left renalhemiazygos route may constitute the main central pathway. although infrequently (Fig. I ). On Cf scans, such communication may be mistaken for a paraaortic mass.

RG analysis of magnetic catalysis in dynamical symmetry breaking

Abstract: We perform the renormalization group analysis on dynamical symmetry breaking under a strong external magnetic field studied recently by Gusynin, Miransky, and Shovkovy. We find that any attractive four-Fermi interaction becomes strong at low energy, thus leading to dynamical symmetry breaking. When the four-Fermi interaction is absent, the $\ensuremath{\beta}$ function for the electromagnetic coupling vanishes in the leading order in $\frac{1}{N}$. By solving the Schwinger-Dyson equation for the fermion propagator, we show that in the $\frac{1}{N}$ expansion, for any electromagnetic coupling, dynamical symmetry breaking occurs due to the presence of a Landau energy gap by the external magnetic field.

The low prevalence of immunogenetic markers in Korean adult-onset IDDM patients.

Abstract: OBJECTIVE IDDM is an autoimmune disease that occurs among genetically susceptible individuals. In Asian populations, it is not uncommon for adult patients with NIDDM to eventually lose β-cell function and develop IDDM. These individuals may be characterized by autoantibodies to GAD and high-risk HLA-DQ alleles, which are unlikely to be prevalent among patients with true NIDDM or in the general population. The objective of the present study was to evaluate and compare the prevalence of these immunogenetic markers in NIDDM patients and healthy nondiabetic individuals from Korea. RESEARCH DESIGN AND METHODS The prevalences of anti-GAD antibodies and HLA-DQA1 and DQB1 alleles among 121 patients with newly diagnosed NIDDM identified from a population-based study in Yonchon, Korea, and 100 matched healthy control subjects were evaluated and compared. RESULTS The overall prevalence of anti-GAD antibodies was 1.7% (2 of 121) in patients with previously undiagnosed NIDDM, whereas 1 of 100 control subjects had a positive test for antibodies. Among those who tested positive, titers of antibodies to GAD were not high. No statistically significant differences in the distributions of either mean levels of anti-GAD antibodies or DQA1 and DQB1 alleles were found comparing NIDDM patients with control subjects. Interestingly, the frequency of DQB1*non-Asp-57 and DQA1*Arg-52 alleles in the Korean adult control population was similar to that in the U.S. white population (DQB1*non-Asp-57: 0.431 vs. 0.475; DQA1*Arg-52: 0.492 vs. 0.463). CONCLUSIONS The low prevalence of anti-GAD antibodies and HLA-DQA1 and DQB1 susceptibility alleles among recent-onset NIDDM patients, which was similar to observations in control subjects, suggests that diabetes in Korean adults is unlikely to have an autoimmune component to its pathogenesis.

Transient fads and the crash of ′87

Abstract: Using a fad model with Markov-switching heteroscedasticity in both the fundamental and fad components (UC-MS model), this paper examines the possibility that the 1987 stock market crash was an example of a short-lived fad. While we usually think of fads as speculative bubbles, what the UC-MS model seems to be picking up is unwarranted pessimism which the market exhibited with the OPEC oil shock and the '87 crash. Furthermore, the conditional variance implied by the UC-MS model captures most of the dynamics in the GARCH specification of stock return volatility. Yet unlike the GARCH measure of volatility, the UC-MS measure of volatility is consistent with volatility reverting to its normal level very quickly after the crash.

Q-switched ruby laser in the treatment of nevus of Ota.

Abstract: The purpose of this study is to evaluate the efficacy of Q-switched ruby laser in the treatment of nevus of Ota, a pigmented lesion on the face. The Q-switched ruby laser has been shown to remove tattoos without scarring. With this in mind, the nevus of Ota with pigmented cells in the dermis could be effectively treated with Q-switched ruby laser. Eighty patients (19 men, and 61 women) with nevus of Ota on the face were enlisted to be tested in evaluating the efficiency of Q-switched ruby laser therapy. The age of patients ranged from 1 to 62 years. The energy fluence used varied from 6 to 8.5 J/cm2. Treatment intervals ranged from 4 to 16 weeks, and the number of treatment sessions varied between 1 to 9 visits. During a 2-year follow-up period, more than fifty percent removal of nevus-pigment was noted in 64 of the 80 patients. Transient hyperpigmentation was noted in 32 patients lasting for 2 to 6 months after treatment; transient hypopigmentation was seen in 3 cases which recovered within one year. No patients had permanent textural or pigmentary changes or scarring. Q-switched ruby laser therapy appears to be an effective and safe modality for the treatment of nevus of Ota.