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There are differing histologic subtypes of gastric cancer. We investigated the clinicopathological features and prognosis of: signet ring cell (SRC), mucinous (MGC), papillary (PGC), and lymphoepithelioma-like (LELC) carcinoma in advanced gastric cancer.One hundred thirty six advanced gastric cancer patients, including 62 SRCs, 43 MGCs, 9 PGCs, and 22 LELCs, who underwent R0 gastrectomy between 2002 and 2013, were retrospectively evaluated.There were significant differences in several clinicopathological features. There were found to be statistical differences in postoperative outcomes in the type of gastrectomy and type of anastomosis (p0.001 and p0.001, respectively). In terms of overall survival analysis, there was no statistical survival difference among the subtypes of advanced gastric cancer (p=0.088). However, LELC had a better prognosis than the other groups.There were some differences in several of the clinicopathological features of the subtypes advanced gastric cancer. Although there were no statistical differences in survival, those with LELC showed a better prognosis than did the other groups. Therefore, the treatment of advanced gastric cancer should be individualized, and prognosis considered, according to the subtype.

Laparoscopy-assisted distal gastrectomy (LADG) has become a viable alternative treatment for patients suffering with early gastric cancer. Surgeons have long thought that obesity might increase the rate of intraoperative or postoperative complications. We set out to clarify the effect that obesity has on performing LADG for the treatment of early gastric cancer.We retrospectively reviewed 97 patients who had undergone LADG for early gastric cancer between May 1998 and March 2004. We measured the degree of obesity by using the body mass index (BMI; kg/m(2)), and we compared the surgical outcomes between the normal BMI group (BMI23 kg/m(2)) and the high BMI group (BMIor = 23 kg/m(2)). We further subdivided the patients into four groups: normal BMI males and normal BMI females, and high BMI males and high BMI females, and we analyzed them in terms of operation times, numbers of retrieved lymph nodes, and rates of postoperative complications.There were no significant differences between the normal and high BMI groups in terms of the patients' characteristics, surgical outcomes, postoperative courses, postoperative complications, and operation times. There were no statistically significant differences in the number of retrieved lymph nodes or in the rate of postoperative complications among the four groups (P = 0.5030 and P = 0.3489, respectively). However, there was a statistically significant difference in operation times among the four groups (P = 0.004). Specifically, the males in the high BMI group required a longer operation time than did the females with a normal BMI (P = 0.006) and the females with a high BMI (P = 0.019).For LADG in patients with early gastric cancer, obesity may affect the operation time, and men with high BMI require a longer operation time than do women with normal or high BMI.

In this paper, an effective nonstationary phase boundary estimation scheme in electrical impedance tomography (EIT) is presented based on the interacting multiple model (IMM) algorithm. The inverse problem is treated as a stochastic nonlinear state estimation problem with the nonstationary phase boundary (state) being estimated online with the aid of the IMM algorithm. In the design of the IMM algorithm multiple models with different process noise covariances are incorporated to improve estimation performance in spite of the modelling uncertainty. Computer simulations are provided to illustrate the proposed algorithm.

The onset of Taylor-Gortler instability induced by an impulsively started rotating cylinder with constant shear stress was analyzed by using propagation theory based on linear theory and momentary instability concept. It is well-known that the primary transient Couette flow is laminar but secondary motion sets in when the inner cylinder velocity exceeds a certain critical value. The dimensionless critical time τ c to mark the onset of instability is presented here as a function of the modified Taylor number T. For the deep-pool case of small τ, since the inner cylinder velocity increases as V i ∝√t in the present impulsive shear system, the present system is more stable than impulsive started case (V i =constant). Based on the present τ c and the Foster’s [1969] comment, the manifest stability guideline is suggested.

An integrated microammonia analysis system (IMAAS) with microreactor and in-plane ( x -axis) type optical source and optical detector with ease and precise optical alignment method using microchannels for optical fiber guide by silicon deep RIE process based on the Berthelot reaction was newly proposed and investigated. It is not necessary to do difficult and complex optical alignment process for ammonia analysis than the case of using out-of-plane ( z -axis) type optical detector perpendicular to microfluidic devices. The proposed IMAAS with the size of 5 cm × 5 cm and thickness of 1 mm was fabricated using typical and simple MEMS processes. IMAAS was packaged with inlet and outlet tube, and optical fiber connected with in-plane type optical source and optical detector using UV epoxy bonding. Reaction rates from ammonia of the concentration of 16.5 ppm to indophenols at IMAAS were remarkably increased with temperatures from 308 to 318 K on hot plate as a heater. In case of reaction temperature of 318 K, complete reaction time was less than 1 min. Reaction rates were increased with ammonia concentrations from 4.1 to 33.0 ppm at the temperatures of 308, 313 and 318 K. In order to remarkably decrease total analysis system, thermoelectric heater of 2 cm × 2 cm was used as a heater. In case of using thermoelectric heater at the temperature of 308 K and the ammonia concentration of 2 ppm, the complete reaction time of indophenol in IMAAS was in the range of 100–150 s. From these results, IMAAS on thermoelectric heater has advantage for small size and local heating of reaction region in IMAAS than the case of using hot plate heater. Fabricated IMAAS were reproducible and suitable for the determination of ammonia concentrations. For the future works, it was thought these microsystems could be used for other microreactions for versatile species analyses as well as detections for N-containing organic species.

The onset of hydrodynamical instability induced by impulsive spin-down to rest in a cylinder containing a Newtonian fluid is analyzed by using the propagation theory. The primary transient swirl flow is laminar but for an initially high rotating speed secondary motion sets in at a certain time. It is found here that the critical Reynolds number Re c = 320 , below which the flow is unconditionally stable. For Re > Re c the dimensionless critical time τ c to mark the onset of a fastest growing instability is presented as a function of the Reynolds number Re. Available experimental data and also predictions show that deviation of the velocity profiles from their primary ones occurs starting from a certain time τ ≈ 4 τ c . This means that secondary motion is detected experimentally at this characteristic time. It seems that during τ c ⩽ τ ⩽ 4 τ c secondary motion is relatively very weak.

The onset of longitudinal vortex rolls in the thermal entrance region of plane Poiseuille flow heated from below with a constant heat flux is investigated theoretically. In the present study, the Boussinesq equations are solved numerically by using the finite volume method to analyze the onset of secondary flow. The local growth rates of the mean temperature and its fluctuations are examined, and the three characteristic distances, which are those to exhibit the onset of intrinsic instability, the detection of secondary flow, and the minimum Nusselt number under mixed convection, are suggested. They are discussed in comparison with available experimental data for water and air.

This work presents a boundary estimation approach in electrical impedance imaging for binary mixture fields based on weighted multi-layered neural network and front point approach. The interfacial boundary is expressed with front points and the unknown front points are estimated with the weighted multi-layered neural network. Numerical experiments show that the proposed electrical resistance imaging approach has a good possibility for the application in the visualization of a binary mixture boundary for real-time monitoring.

When a nonhomogeneous solid is melting from below, convection may be induced in a thermally–unstable melt layer. In this study, the onset of buoyancy-driven convection during time-dependent melting is investigated by using similarly transformed disturbance equations. The critical Darcy–Rayleigh numbers based on the melt-layer thickness, RaH,c, are found numerically for various conditions. For small superheats, the present predictions show that RaH,c is located between 27.1 and 4π2 and it approaches the well-known results of the original Horton–Rogers–Lapwood problem. However, for high superheats, it is dependent on the phase change rate λ and the relation of RaH,c λ = 25.89 is shown.

Numerical works are conducted to develop a visualization technique for the phase distribution in a two-phase system by electrical impedance tomography (EIT) technique, which reconstructs the conductivity distribution with the electrical responses that are determined by corresponding excitations. For the two-phase flow system, the impedance of each phase can be known – but here the phase boundary depending on the distribution of dispersed phase is of particular interest. In the present study, the image reconstruction problem is derived as a boundary estimation one and a new algorithm is developed for the estimation of phase boundary based on the front points tracking technique. To test the robustness of the proposed algorithm, some numerical simulations are conducted. Numerical works show that the proposed algorithm can treat two-phase systems reasonably even with some errors in measurement data.

A theoretical analysis of thermal instability driven by buoyancy forces under a time-dependent temperature field of conduction is conducted in an initially quiescent, horizontal liquid layer. The dependency of viscosity on temperature is considered and the propagation theory is employed for the stability analysis. For large Prandtl number systems, the critical condition of the onset of buoyancy-driven convection is obtained as a function of the Rayleigh number and also the viscosity contrast and it is compared with available experimental data. It is evident that the growth period is required until the growing instabilities are detected experimentally, which is dependent upon the viscosity contrast.

This work presents a boundary estimation approach in electrical resistance imaging for binary mixture fields based on weighted multilayer neural network. The interfacial boundaries are expressed with the truncated Fourier series and the unknown Fourier coefficients are estimated with the weighted multilayer neural network. In doing so, normalized boundary voltages are used for training the neural network and the results from real experiments show that the proposed approach has strong possibility for real-time monitoring of binary mixtures

The onset of Taylor–Gortler instability induced by a linearly accelerated inner cylinder in Couette flow is analyzed by using the propagation theory based on linear theory and momentary instability concept. It is well-known that the primary transient Couette flow is laminar but secondary motion sets in when the inner cylinder velocity exceeds a certain value. The dimensionless critical time τ c to mark the onset of instability is presented here as a function of the modified Taylor number T. Available experimental data indicate that for large T secondary motion is detected starting from a certain time τ ≈ 2 τ c . This means that the growth period of initiated instabilities is needed for secondary motion to be detected experimentally. It seems evident that during τ c ⩽ τ ⩽ 2 τ c secondary motion is relatively very weak and the primary diffusive momentum transfer is dominant.

The onset of mixed convection in a fluid-saturated porous layer between two horizontal plates heated from below with a constant heat flux is investigated theoretically. In the present study, the Darcy model is applied and the resulting nonlinear equations are solved by using the finite volume method. In order to analyze the growth behavior of convective instabilities, the local growth rates of mean temperature and its fluctuations are examined. Based on the numerical results, characteristic distances to represent the onset of secondary flow and also the manifestation of mixed convection are clarified to a certain degree in comparison with available experimental data. The critical distance to mark the onset of intrinsic thermal instability is predicted from a new stability criterion. It is interesting that the propagation theory yields almost the same critical conditions as the numerical ones. © 2006 American Institute of Chemical Engineers AIChE J, 2006

The onset of buoyancy-driven convection in an initially quiescent, horizontal nanoparticles suspension layer heated from above is analyzed theoretically. In this thermally-stable stratified fluid layer, the Soret diffusion can induce buoyancy-driven motion for the case of the negative separation ratio. For the high solutal Rayleigh number, the convective motion sets in during the transient diffusion stage and the onset time of this motion is analyzed by employing the propagation theory. Here the stability criteria are obtained and the predicted critical time to mark the onset of convective motion, τc, is compared with available experimental data. It is shown that convective motion can be detected starting from a certain time τm ≅ 4τc. © 2006 American Institute of Chemical Engineers AIChE J, 2006

The onset time of double-diffusive convection in time-dependent, nonlinear concentration fields was investigated theoretically and experimentally. The stability analysis was conducted on the basis of the propagation theory. Under the linear stability theory, the linearized perturbation equations were transformed similarly by using the concentration penetration depth as a length-scaling factor. The newly derived stability equations were solved numerically. Also the onset time was determined experimentally by employing an electrochemical technique where 0.03–0.3 M CuSO 4 + 1.5 M H 2 SO 4 aqueous solutions were adopted as electrolyte. The onset time of double-diffusive convection was delayed or shortened depending on the degree of stable stratification.

Uncertainty with the safety of the biofragmentable anastomosis ring makes surgeons hesitate in its widespread use in intestinal surgery. This study was designed to evaluate the validity of the biofragmentable anastomosis ring as a routine anastomotic device in enterocolic surgery. The study analyzed the nine-year experience of 632 biofragmentable anastomosis ring anastomoses performed in 617 patients: 525 (83 percent) as elective procedures and 107 (17 percent) as emergency. Three classic types of anastomosis, end-to-end (n = 354), end-to-side (n = 263), and side-to-side (n = 15), were performed with a standard technique. Anastomotic sites included ileocolic/ileorectal in 283 patients (45 percent), colorectal in 148 (23 percent), enteroenteric in 101 (16 percent), and colocolic in 100 patients (16 percent). Anastomotic leakage with clinical relevance was observed in five patients (0.8 percent): three elective cases, and two emergency (2 colorectal anastomoses and 1 ileorectal required diversions). Among 13 instances (2.1 percent) with postoperative intestinal obstruction, only 1 required relaparotomy for closed-loop obstruction. Seven patients (1.1 percent; 4 elective cases, and 3 emergency) died postoperatively; no deaths were directly related to the biofragmentable anastomosis ring technique. Our data suggest that the anastomosis using the biofragmentable anastomosis ring is a uniform and highly reliable technique even in high-risk emergency surgery. Along with its clinical validities, clinical application of the biofragmentable anastomosis ring in different types of anastomoses in enterocolic surgery is expected to be expanded with a high level of technical safety.

The onset of buoyancy-driven convection in an initially isothermal, quiescent fluid layer heated from below with a constant heating rate is analyzed by the propagation theory. Here the dimensionless critical time τ c to mark the onset of convective motion is presented as a function of the Rayleigh number Ra φ and the Prandtl number Pr. The present stability analysis predicts that for a given large Ra φ , τ c decreases with increasing Pr and it is independent of the conditions of the upper boundary. For deep-pool systems, the deviation of the temperature profile from conduction state occurs starting from a certain time τ o ≅ 4 τ c . The present predictions are compared with other models and existing experimental results in the whole time domain.

Numerical and experimental works are conducted to develop a visualization technique for the phase distribution in a two-phase system by electrical impedance tomography technique, which reconstructs the resistivity distribution with the electrical responses that are determined by corresponding excitations. In conventional Newton–Raphson method, the flow field is discretized into pixels, each of which has an unknown resistivity value to be determined by the image reconstruction algorithm. The pixels are usually fixed in a predetermined way. In practical cases, such as the impedance imaging of two-phase flow, this model might not be useful. For the two-phase flow system, the impedance of each phase does not change but instead the phase boundary depends on the distribution of dispersed phase. In the present study, a new image reconstruction algorithm employing adaptive mesh regeneration technique is developed for the detection of phase boundary. Numerical works show that the proposed method can treat two-phase systems reasonably even with some errors in measurement data. Also, with an apparatus developed for impedance imaging this study attempts to reconstruct the images of the simulated bubble distributions and the reconstructed images imply the potential possibility of the electrical impedance tomography for the two-phase flow visualization.

Summary Aim The aim of this study was to determine the feasibility of laparoscopy-assisted gastrectomy (LAG) with extraperigastric lymph node dissection for gastric cancer. Methods The authors attempted LAG with extraperigastric lymph node dissection in 117 consecutive gastric cancer patients between May 1998 and January 2004. The clinico-pathologic characteristics, operative outcomes, post-operative morbidities and mortalities, and follow-up findings of patients with advanced gastric cancer were evaluated. Results LAG with extraperigastric lymph node dissection were successfully performed in 114 of 117 patients (success rate, 97%). Of these 114 successful cases, 100 cases were early gastric cancers and 14 cases were advanced gastric cancers. The mean operation time for the 114 cases was 259 (range 150–415) min, and the mean number of retrieved lymph nodes was 23 (range 6–66). Operative mortality, hospital death, and overall post-operative complication rates were 0, 1.7 and 14.7%, respectively. Follow-up was available in 110 of the 112 patients (two post-operative hospital deaths were excluded from the 114). Follow-up ranged from 6 to 74 months (median: 19). 108 patients remain alive without recurrence or port-site metastasis. Conclusions LAG with extraperigastric lymph node dissection is a technically feasible and acceptable method for the surgical treatment of gastric cancer.

This study presents a visualization technique for the phase distribution in a two-phase flow field with electrical impedance imaging technique, which reconstructs the resistivity distribution with electrical responses that are determined by corresponding excitations. Special emphasis is placed on the development of dynamic imaging technique for two-phase system undergoing rapid transient, which could not be visualized with conventional static imaging techniques. The proposed algorithm treats the image reconstruction problem as a nonlinear state estimation problem and the unknown state (resistivity distribution, i.e. phase distribution) is estimated with the aid of Kalman filter in a minimum mean square error sense. With computer simulations, some issues arisen in the application to two-phase flows are discussed and the performance of the proposed algorithm is examined.

In this study, the electrical impedance imaging of two-phase flows undergoing rapid transient is considered with a special emphasis on the effect of the current pattern on the image reconstruction. As observed in the companion paper, the trigonometric current pattern, which is commonly used in the conventional static electrical impedance imaging, shows poor performance in case of the dynamic imaging considered in this work. Extensive numerical experiments are conducted with various kinds of current patterns and their effects on the image reconstruction performance are examined. The results indicate that the trigonometric patterns with lower modes are preferable.

In this paper, an effective dynamical EIT imaging scheme is presented for on-line monitoring of the abruptly changing resistivity distribution inside the object, based on the interacting multiple model (IMM) algorithm. The inverse problem is treated as a stochastic nonlinear state estimation problem with the time-varying resistivity (state) being estimated on-line with the aid of the IMM algorithm. In the design of the IMM algorithm multiple models with different process noise covariance are incorporated to reduce the modeling uncertainty. Simulations and phantom experiments are provided to illustrate the proposed algorithm.

A theoretical analysis of thermal instability driven by buoyancy forces in transient temperature fields is conducted in an initially quiescent, fluid-saturated, horizontal porous layer. Darcy's law is used to explain characteristics of fluid motion and linear stability theory is employed to predict the onset of buoyancy-driven motion. Under the principle of exchange of stabilities, the stability analysis is performed on the basis of the linear amplification theory. The result predicts the critical condition of onset of buoyancy-driven convection, which is governed by the Darcy-Rayleigh number. The present stability criteria predict the experimental data quite well.

The onset of initial instability in a developing Couette flow following the impulsive starting of an inner rotating cylinder is analyzed using linear theory. It is well known that there is a critical Taylor number Ta c at which Taylor vortices first appear between two concentric cylinders. For Ta > Ta c Taylor-like vortices occur at a certain elapsed time. In the present study, the critical time t c to represent the onset of this initiating instability, which then grows as toroidal vortices, is analyzed using propagation theory. For this purpose a self-similar transformation is forced through scaling analysis. The resulting stability criteria compare well with the available experimental data for vortices in water. The new measures represent the onset of the fastest growing instability and also suggest the detection time for the manifestation of secondary flow in the primary time-dependent Couette flow.

Design and fabrication of micro mixing cells and detection cells were investigated. Glass micro mixing cells with island structures among channels were fabricated using sand blaster methods. Depth and width of mixing channel were 200 ㎛ and 180 ㎛ and island size was 90 ㎛ by 90 ㎛. Two 45° mirrors surfaces faced on each other in one detection cell which were fabricated by silicon anisotropic etching using 20% TMAH (Tetramethylammonium hydroxide) solution with 20% or 30% IPA (iso propyl alcohol) at 80°C, respectively. Up side glass wafer for mixing cell and down side silicon wafer for detection cell were bonded using anodic bonding method at 350ı, -600 V and 300 N. Synthetic indophenol was injected at inlet and moved to the detection cell through the mixing channel. HeNe laser of 632.8 nm was focused on one side of a 45° mirror, and passed through indophenol solution until the other side of a 45° mirror. The light of 632.8 nm was absorbed in indophenol solution between two 45° mirrors at detection cell. By the Beer-Lambert’s law, indophenol concentration could be calculated from the measured result of the absorbance.

A programme of condensation experiments was carried out at atmospheric pressure using a water-cooled flat plate varying the air concentrations, the plate inclination and its orientation (upward or downward facing). Rates of heat transfer have been measured on a single face of the condensing plate suspended in a cylindrical test section as steam and mixtures of steam and air flowed over it. The rate of heat transfer decreased as the angle of the plate to the horizontal was reduced and as the concentration of air was increased. A notable observation was that comparison of results for the upward and downward facing cases showed that the heat transfer rates with pure steam are higher for an upward facing plate than for a downward facing one. However, with air present in the steam, this trend is reversed. The effects of plate orientation, mixture flows and buoyancy are discussed.

Background and Objectives Laparoscopy-assisted gastrectomy with lymph node dissection for gastric cancer is considered technically more complicated than the open method. Moreover, the safety and efficacy of laparoscopy-assisted distal gastrectomy (LADG) with extraperigastric lymph node dissection in patients with gastric cancer have not been established yet. To evaluate short-term surgical validity, surgical outcome of the laparoscopy-assisted distal gastrectomy (LADG) with extraperigastric lymph node dissection was compared with that of the conventional open distal gastrectomy (CODG) in patients with early gastric cancer. Methods One hundred and forty-seven patients with early gastric cancer received radical distal gastrectomy during 2002 and 2003, where LADG was undergone in 71 patients. The clinicopathologic characteristics, postoperative outcomes and courses, and postoperative morbidities and mortalities were compared between the two groups. Data were retrieved from the stomach cancer database at Dong-A University Medical center. Results Baseline characteristics, including sex, age, body mass index (BMI), American Society of Anesthesiology (ASA) class, tumor size, T stage, and lymph node metastasis were similar between the two groups. No significant differences were found between these groups in terms of the number of retrieved lymph nodes with respect to D1 + α (D1 + no. 7) and D1 + β (D1 + no. 7, 8a, and 9) lymphadenectomy. In the LADG group, wound size was smaller (P

The onset of instability in the flow by an impulsively started rotating cylinder is analyzed under linear theory. It is well-known that at the critical Taylor number Tc=1695 the secondary flow in form of Taylor vortices sets in under the narrow-gap approximation. Here the dimensionless critical time τc to mark the onset of instability for T≫Tc is presented as a function of the Taylor number T. Available experimental data of water indicate that deviation of the velocity profiles from the primary flow occurs starting from a certain time τ≅4τc. It seems evident that during τc≤τ≤4τc the secondary flow is very weak and the primary state of time-dependent annular Couette flow is maintained.

We present an integral approach to estimate temperature-dependent thermal conductivity and heat capacity per unit volume simultaneously in a transient non-linear heat conduction medium. It is assumed that the thermal property is a monotonic function of the temperature and it can be expressed as a piecewise linear function. Hence, the present inverse heat conduction problem is converted to a parameter identification problem determining the unknown coefficients of the model functions of the thermal conductivity and heat capacity per unit volume. The spatial temperature distribution required for the integral approach is modeled as a third-order function of position in a one-dimensional heat conduction domain with heated and insulated walls. Four coefficients of the approximated temperature distribution are determined from the heat fluxes imposed and the temperatures measured at both ends at each measurement. Hence, the proposed algorithm does not require any internal measurements

Electrical impedance tomography (EIT) is a relatively new imaging modality in which the internal impedivity distribution is reconstructed based on the known sets of injected currents and measured voltages on the surface of the object. In this paper, an effective EIT imaging scheme is presented for on-line monitoring of the time-varying resistivity distribution inside the object based on the interacting multiple model (IMM) algorithm. The inverse problem is treated as a nonlinear state estimation problem and time-varying resistivity (state) is estimated on-line with the aid of the IMM algorithm. In doing so, multiple kinematic models are employed as the state evolution model to reduce the modelling uncertainty. Computer simulations are provided to illustrate the reconstruction performance of the proposed algorithm.

The onset of buoyancy-driven convection in an initially isothermal, quiescent fluid layer confined between the two infinite horizontal plates is analyzed by using propagation theory. For the system heated rapidly from below with a constant heat flux, the dimensionless critical time τ c to mark the onset of convective instability is presented as a function of the Rayleigh number and the Prandtl number. The present predictions show that τ c decreases with increasing Prandtl number for a given Rayleigh number. Available experimental data for water and silicone oil indicate that visible motion is detected first and then, an obvious deviation of the heated surface temperature from its conduction solution occurs. The difficulty of defining the detection time of visible motion is discussed in comparison with experiments.

We introduce the electrical impedance tomography (EIT) technique for the possible application to the visualization of binary- and ternary-mixture systems. In the EIT, the internal image is reconstructed from the resistivity (or conductivity) distribution obtained by the image reconstruction algorithm, which solves the EIT inverse problem with the relationship between the predetermined electrical excitations and the corresponding responses measured at the system boundary. In this study, a 32-electrode EIT measurement system is developed and is utilized for imaging several simulated binary-and ternary-mixture systems

The temporal evolution of buoyancy-driven convection in an initially quiescent and stably-stratified fluid layer confined between two horizontal plates is investigated theoretically. After the temperature of the bottom plate is increased suddenly to a higher one, buoyancy-driven convection appears at a certain time. In order to trace the related time-dependent thermal behavior, the Boussinesq equations are solved numerically by using the finite element method to examine the growth rates of the basic temperature field and its fluctuations with time. Based on the numerical results, the characteristic times to mark the onset of intrinsic instability, the first detection of convective motion and the ensuing manifestation of convection are illustrated by a set of new parameters suggested here. The latter two characteristic times are discussed in comparison with the experimental data available in the literature.

A theoretical analysis of thermal instability driven by buoyancy forces in transient temperature fields is conducted in an initially quiescent, horizontal fluid layer heated from below and cooled from above with uniform heat flux. Linear stability theory is employed to predict the onset of buoyancy-driven motion. Under the principle of exchange of stabilities, the stability analysis is performed on the basis of the propagation theory which adopts the concentration boundary layer thickness as a characteristic length scaling factor

The onset of hydrodynamical instability induced by impulsive spin-down to rest in a cylinder containing a Newtonian fluid is analyzed by using propagation theory. It is well-known that the primary transient swirl flow is laminar, but with initial high velocities secondary motion sets in at a certain time. The dimensionless critical time Τc to mark the onset of instability is presented here as a function of the Reynolds number Re. Available experimental data indicate that for large Re deviation of the velocity profiles from their momentum diffusion occurs starting from a certain time Τ≈4Τc. This means that secondary motion is detected at this characteristic time. It seems evident that during Τc⪯Τ⪯4Τc, secondary motion is relatively very weak and the primary diffusive momentum transfer is dominant.

The effects of the flowing mixture of steam and air to the condensation heat transfer were investigated experimentally at atmospheric pressure varying the air concentration. Rates of heat transfer have been measured on a single face of a water-cooled flat plate suspended vertically in a cylindrical test section as steam and mixtures of steam and air flowed over it. The measured heat transfer rates for the pure steam case showed good agreements with the Nusselt theory of natural convection condensation. However, in the steam and air mixture cases, the small mixture flows enhanced the heat transfer rates. The measured heat transfer rates were within the envelops of natural and forced convection condensations with more shift to the force convection condensation. At large sub-cooling temperatures, the ratios of heat flux with and without air increased by the stronger sweeping effect of the mixture flows to the thicker air-rich layers

The electrical impedance tomography (EIT) technique is introduced for visualizing two-phase systems. The finite element method is employed to solve the electrical field induced by the currents through electrodes placed along the boundary, and a modified Newton–Raphson iterative method is used to determine the search step minimizing the error between the calculated and the measured voltages at the electrodes. However, even for a two-phase system, the conventional Newton–Raphson method cannot increase the spatial resolution after a certain iteration step. To resolve this problem, an adaptive element grouping technique is introduced. A new image reconstruction algorithm is tested for the synthetic data and phantom experimental data. It seems that the proposed algorithm is useful for the improvement of EIT performance in the application to the visualization of two-phase systems.

The onset of thermal convection in an isothermally heated, horizontal porous layer saturated with viscoelastic liquid was analyzed analytically under the linear theory. An existing constitutive model, which is rather simple, was employed to examine the effects of relaxation times. It is shown clearly that oscillatory instabilities can set in before stationary modes are exhibited. The peculiar behavior of the frequency at the critical state was discussed in connection to polymeric liquids.

The onset of buoyancy-driven convection in plane Couette flow heated uniformly from below is analyzed theoretically. For the thermal entrance region with Ra q ≫816.7, a new set of stability equations involving streamwise variations of disturbances are derived based on the linear theory, the scaling relations and the extended momentary instability concept. It is shown that the critical Rayleigh number that marks the onset of longitudinal vortex rolls increases with a decrease in Prandtl number. Based on the present stability criteria a new mixed convection heat transfer correlation is derived for the whole range of Rayleigh number. The present analysis predicts the available experimental data of water, quite well.

The azimuthal momentum transport plays an important role in the flow field through non-circular domain. In order to obtain the information on the azimuthal momentum transport in infinitely arrayed rod bundles theoretically, an integral analysis is performed on the axial momentum equation. By integrating the axial momentum equation from the wall to the maximum velocity line, a simple and useful relation between the integral azimuthal momentum transport and the wall shear stress distribution is derived in terms of the azimuthal angle and the pitch-to-diameter. The contribution of azimuthal Reynolds stress and secondary flow to the azimuthal momentum transport is analyzed for well-known experimental data. It is expected that the derived relation may be useful to understand the turbulent structure in rod bundles and to confirm the experimental results for azimuthal Reynolds stress and secondary flows as well

An inverse problem is solved to obtain the particle concentration profile in suspension under pressuredriven flow with electrical impedance tomography (EIT). The finite element method (FEM) is employed in the forward problem and the regularized Newton-Raphson iterative method is used in the inverse problem. Different FEM meshes are used in the forward and the inverse problem not to commit inverse crime. To avoid post-calibration of measurement data, the complete electrode model is introduced. For the evaluation of the robustness of the reconstruction algorithm, several testing cases with measurement error are considered. The proposed algorithm can be used to reconstruct the particle concentration in suspension.

We present a non-iterative direct method to estimate time-varying boundary heat flux in a one-dimensional heat conduction domain with heated and insulated walls. The proposed method relates the temporal variation of the surface heat flux to the temperature variation at the heated surface based on the analytical temperature distribution. Several illustrative examples are examined to verify the performance of the proposed method. The uncertainty analysis of the estimated heat fluxes is discussed. The proposed method may also be useful to make sufficiently accurate initial guesses for more sophisticated method which usually adopt the iterative scheme

In electrical impedance tomography (EIT), cross-sectional resistivity distribution is reconstructed using current and voltage measurements made from the boundary. In this paper, a novel adaptive mesh-grouping scheme is presented to enhance the spatial resolution of the Gauss-Newton algorithm in two-phase fields. Experimental results are provided to illustrate the effectiveness of the proposed scheme.

This paper introduces ISAAC (An Interface for Sentence Analysis & Abstraction with Cogitation) which provides an integrated user interface for sentence analysis. Into ISAAC, the various linguistic tools and resources are integrated. They are necessary for sentence analysis. Most of the tools and resources for sentence analysis are developed and accumulated independently. In the sentence analyzing with these tools and resources, it is difficult for sentence analyst to manage and control information which is taken on each step. In this respect, we have integrated the usable tools and resources, and made ISAAC to provide the consistent user oriented interface to each function. We have been able to divide sentence analysis process Into 14 steps. In ISAAC, these steps are processed by four individual modules ①syntactic analysis of sentence, ②retrieval of a root word, ③searching category information in Roget's Thesaurus, and ④searching category information in OfN(Ontology for Narratives). Therefore, in case of sentence analysis with ISAAC, the process of total 14 steps falls into 4 steps. This means that it is able to improve the performance of sentence analyst to the extent 3.5 times or more. Furthermore, ISAAC undertaking tedious transcription needed to process each step, we expect that ISAAC can help the analyst to maintain the accuracy of sentence analysis.

In the conventional electrical impedance tomography (EIT), the internal impedivity distribution, that is mixture distribution, is reconstructed based on the physical relationship between the known sets of injected currents through the electrodes and induced voltages on the surface of the domain of interest under the assumpution that the domain is stationary during the measurements. This study considers a dynamic electrical impedance imaging to binary-mixture systems with known internal structures to which additional electrodes can be attached. We attempt the utilization of the additional electrodes to enhance the recontruction. Also, we assume the domain is undergoing rapid transient, so the resistivity distribution in the domain of interest changes rapidly within the time taken to acquire a full set of independent measurement data. The dynamic EIT problem is treated as the nonlinear state estimation problem and the unknown state (resistivity) is estimated with the aid of extended Kalman filter in a minim...

The onset of buoyancy-driven convection in an initially isothermal, quiescent fluid layer heated from below with time-dependent manner is analyzed by using propagation theory. Here the dimensionless critical time Τc to mark the onset of convective instability is presented as a function of the Rayleigh number RaO and the Prandtl number Pr. The present stability analysis predicts that Τc decreases with increasing Pr for a given RaO. The present predictions compare reasonably well with existing experimental results. It is found that in deep-pool systems the deviation of temperature profiles from conduction state occurs starting from a certain time Τ≏(2∼4) Τc .

A theoretical analysis of convective instability is conducted in an initially quiescent, fluid-saturated, horizontal porous layer heated from below with constant heat flux. Darcy's law is used to model the fluid motion and linear stability theory is employed to predict the onset of buoyancy-driven convective motion. Under the principle of exchange of stabilities, the stability analysis is performed on the basis of the propagation theory which adopts the thermal penetration depth as a characteristic length scaling factor. The result predicts the critical condition of onset of buoyancy-driven convection which is governed by the Darcy-Rayleigh number

The temporal development of thermal disturbances in the fluid layer heated isothermally from below is investigated, based on propagation theory. This theory is examined by using scaling. To examine the behavior of thermal instability the mean-field approximation is employed and resulting equations are solved by Galerkin method. The stability criteria to mark the onset of convective instability are newly suggested as the intersection point of the growth rate of averaged temperature with that of its fluctuation. The resulting critical time is close to that derived from propagation theory. By considering the nonlinear effects, the characteristic times to represent the detection time of manifest convection and also to exhibit the minimum Nusselt number are discussed.

The surface diffusion characteristics of nonpolar perfluoropolyether (PFPE) Z on carbon surfaces are investigated in two regimes, submonolayer and multilayer, for nano-thin films. For the submonolayer regime, the two-dimensional, cubic van der Waals equation of state is applied to determine the dependence of the surface diffusion coefficient on the film thickness, as experimental surface diffusion coefficients increase with increasing film thickness. For the multilayer regime, a conventional fluid mechanics analysis with position dependent viscosity and a van der Waals disjoining pressure gradient is applied to investigate the surface diffusion characteristics. The present theoretical analysis qualitatively agrees with the experimental results.