Dong-Kyun Woo

Microsatellite Instability in the Adenoma-Carcinoma Sequence of the Stomach

Sixty-three cases of stomach resections harboring both adenoma and carcinoma were analyzed for microsatellite instability (MSI). The cases included 28 carcinomas arising from adenoma (Type I) and 35 carcinomas with separate adenoma (Type II). The results of MSI assessed by 49 markers were the same for BAT-26 instability. The incidence of MSI was 21% in gastric adenoma and 30% in gastric carcinoma, which is significantly higher than gastric carcinoma without associated adenoma (p < 0.01). Five of eight (63%) cases of multiple carcinomas associated with adenoma showed MSI+ in adenoma and in one or more carcinoma lesion(s). Eight of thirteen (62%) MSI+ adenomas were associated with carcinoma, whereas 20 of 50 (40%) MSI− adenomas were associated with carcinoma. MSI+ adenomas of Type I showed a higher mutation rate of the TGF-β RII gene than Type II (88% versus 40%). Gastric adenoma with TGF-β RII gene mutation was more prone to transform into carcinoma (p = 0.03). This study revealed that gastric carcinoma arising from adenoma is frequently associated with a mismatch repair deficiency mechanism. In the gastric adenoma-carcinoma sequence, TGF-β RII gene mutation occurred early in the adenoma stage and it persisted after malignant transformation.

A Novel Multimodal Optimization Algorithm Applied to Electromagnetic Optimization

The selection of optimum parameters in electromagnetic design usually requires optimization of multimodal, nonlinear functions. This leads to extensive calculations which pose a huge inconvenience in the design process. This paper proposes a novel algorithm for dealing efficiently with this issue. The proposed algorithm interprets the problem as an unexplored terrain for climbing. Through the use of contour line concept coupled with Kriging, the algorithm finds out all the peaks in the problem domain with as few function calls as possible. The efficiency of the proposed algorithm is demonstrated by application to conventional test functions. In this paper, the simulation results show that skewing does not necessarily reduce the cogging torque but may cause it to increase for certain pole-arc to pole-pitch ratio. The developed algorithm is applied to the magnet shape optimization of an axial flux permanent magnet synchronous machine and the cogging torque was reduced to 79.8% of the initial one.

Analysis and Design of a Multi-Layered and Multi-Segmented Interior Permanent Magnet Motor by Using an Analytic Method

Although demand for the multi-segmented and multi-layered (MSML) interior permanent magnet (IPM) motor is high, the analytic method for this motor has not yet been proposed. The finite element method has been used in the analysis and design of the MSML IPM motor, even though it takes much time to perform. To solve this problem, the correct and rapid analytic analysis method for the MSML IPM motor is proposed in this paper. This method is called the MCC method because it is the combination of the Magnetic equivalent circuit, Conformal mapping to consider slotting effect, and Concentration flux of IPM. Furthermore, the feasibility of the optimization of the MSML motor by using the proposed MCC method is verified in this paper.

A Study on Loss Characteristics of IPMSM for FCEV Considering the Rotating Field

This paper presented the loss characteristics of interior permanent-magnet machines (IPMSM) for a fuel-cell electric vehicle. In order to study the loss characteristics of the machine, one prototype machine having 100 [kW] was designed. In the analysis, to consider the harmonic magnetic field and the rotational variation of flux vectors in the core of the machine effectively, we proposed a new harmonic iron-loss calculation method based on adaptive loss coefficients. To verify the performance of the proposed method, we calculated a no-load iron loss in an IPMSM with conventional methods. Then, the estimated iron losses were compared with the experimental data. It was clarified that the proposed method is more effective than conventional methods at high-speed operation. Based on this proposed method, we investigated the losses of the machine considering operating points according to its speed. From the results, it was shown that the main loss component and the location of iron-loss distribution change depending on operating condition.

Cogging Torque Minimization of a Dual-Type Axial-Flux Permanent Magnet Motor Using a Novel Optimization Algorithm

The design of an electric machine is a multivariable and multimodal problem that requires much time to find the optimal design result. To address this problem, we propose a novel optimization algorithm using a kriging meta-model, a contour face climb method, a reinterpolation method in an expected region, an advanced pattern search method, and a uniform search method in the entire problem space. A rapid, exact, and reliable optimization process for a multivariable and multimodal design problem is possible using the proposed novel algorithm. Its validity was confirmed by comparing the optimization results of a test function with evolutionary optimization methods. For verification of the application to an electric machine, a dual-rotor axial flux permanent-magnet synchronous motor was designed using the proposed algorithm in this paper.

p53, p16 and RB expression in adenosquamous and squamous cell carcinomas of the stomach.

The expression of p53, p16 and RB proteins and their clinicopathologic correlation were investigated in 15 cases of primary gastric adenosquamous carcinoma and 2 cases of squamous cell carcinoma of the stomach. The male to female ratio of the patients was 13:4 and the average age was 55.7 years. None of the cases was early gastric carcinoma, and none of the adenocarcinoma components were of the diffuse or signet ring cell types. Fourteen cases showed metastasis to regional lymph nodes and/or other organs at the time of surgery. The adenocarcinoma component was metastasized to lymph nodes in 12 cases, and both adenocarcinoma and squamous cell carcinoma components were metastasized in three cases. The altered expression of p53 correlated with the advanced stage, but did not correlate with the depth of invasion, lymph node metastasis or recurrence. The altered expression of p16 and RB proteins did not correlate with any of the above clinico-pathologic factors. Both the adenocarcinoma and squamous cell carcinoma components revealed an inverse correlation between the expression pattern of p16 and RB proteins (p < 0.05). This suggests that the two proteins share a role in the carcinogenesis of these tumors. The expression pattern of p53 proteins in the adenocarcinoma and squamous cell carcinoma components was exactly the same in all of the cases. The expression patterns of p16 and RB protein were also identical in most of the cases. The expression patterns of all three proteins in the metastatic lesions were also identical to those in the primary lesions. The fact that the alteration of the three tumor suppressor gene products shares the same pattern suggests that squamous and adenocarcinoma components in the stomach originate from the same or a genetically related clone.

Optimal Rotor Structure Design of Interior Permanent Magnet Synchronous Machine based on Efficient Genetic Algorithm Using Kriging Model

In the recent past, genetic algorithm (GA) and evolutionary optimization scheme have become increasingly popular for the design of electromagnetic (EM) devices. However, the conventional GA suffers from computational drawback and parameter dependency when applied to a computationally expensive problem, such as practical EM optimization design. To overcome these issues, a hybrid optimization scheme using GA in conjunction with Kriging is proposed. The algorithm is validated by using two mathematical problems and by optimizing rotor structure of interior permanent magnet synchronous machine.

Characteristic Analysis for IPMSM Considering Flux-Linkage Ripple

In a multi-layer interior permanent magnet synchronous motor, the d- and q-axis parameters vary nonlinearly according to different load conditions, consequently changing the level of saturation. The flux-linkage of d- and q-axis conveys ripple characteristics resulting from mechanical structure and degree of magnetic saturation. If the calculated flux-linkage is correct, the torque using the Maxwell stress tensor method is the same torque calculated by the flux-linkage. However, discrepancy between results exists. In this paper, the d- and q-axis flux-linkage, in consideration of the ripple characteristic, is calculated. Simulation results are then compared with experimental results.

Novel Electromagnetic Actuator Using a Permanent Magnet and an Inter-Locking Mechanism for a Magnetic Switch

The solenoid magnetic actuator has been widely used as an actuator for MS (magnetic switch). Thus, conventional MSs continuously consume electrical power to maintain a closed state. To address this problem, an innovative structure which uses a permanent magnet to generate holding force in the closed state without electrical power is suggested in this paper. Further, the permanent magnet is dedicated to the opening operation and the closing operation by means of its magnetic force. In other words, an eco-friendly MS is proposed in this research. However, this structure has a critical problem in that, if unexpected external force is applied to the MS when in the open state, the MS returns to the closed state by the force of the permanent magnet and remains in the closed state, causing an unintended operation of the load. To solve this problem, a novel inter-locking mechanism is proposed. Hence, we termed the proposed novel MS the MSPI (magnetic switch using a permanent magnet and an inter-locking system). In addition, analysis and design methods for the MSPI are proposed in this paper. The usefulness of the MSPI and the accuracy of the analysis and design methods are confirmed through an experiment.

A 2-D Finite-Element Analysis for a Permanent Magnet Synchronous Motor Taking an Overhang Effect Into Consideration

In the two-dimensional (2-D) finite-element (FE) analysis, the overhang effect can be considered through an increase in the remanence flux density of the permanent magnet in order to reflect the increment of the air-gap flux density due to the overhang structure. However, a repetitive 2-D FE analysis was performed in order to match the air-gap flux density with it in the three-dimensional (3-D) FE analysis. The proposed method accurately accounts for the overhang effect without trial and error. From the results of the 3-D FE analysis, the validity of the proposed method is verified.