• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.233-239
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• 2022

The injection molding process is a process in which thermoplastic resin is heated and made into a fluid state, injected under pressure into the cavity of a mold, and then cooled in the mold to produce a product identical to the shape of the cavity of the mold. It is a process that enables mass production and complex shapes, and various factors such as resin temperature, mold temperature, injection speed, and pressure affect product quality. In the data collected at the manufacturing site, there is a lot of data related to good products, but there is little data related to defective products, resulting in serious data imbalance. In order to efficiently solve this data imbalance, undersampling, oversampling, and composite sampling are usally applied. In this study, oversampling techniques such as random oversampling (ROS), minority class oversampling (SMOTE), ADASYN(Adaptive Synthetic Sampling), etc., which amplify data of the minority class by the majority class, and complex sampling using both undersampling and oversampling, are applied. For composite sampling, SMOTE+ENN and SMOTE+Tomek were used. Artificial neural network techniques is used to predict product quality. Especially, MLP and RNN are applied as artificial neural network techniques, and optimization of various parameters for MLP and RNN is required. In this study, we proposed an SA technique that optimizes the choice of the sampling method, the ratio of minority classes for sampling method, the batch size and the number of hidden layer units for parameters of MLP and RNN. The existing sampling methods and the proposed SA method were compared using accuracy, precision, recall, and F1 Score to prove the superiority of the proposed method.

• International Journal of Quality Innovation
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• v.4 no.1
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• pp.191-204
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• 2003

The target costing technique, mathematically discussed by Sauers, only uses the $C_p index along with Taguchi loss function and $\bar{X}$-P control charts to setup goal control limits. The new specification limits derived from Taguchi loss function is linked through the $C_p value to $\bar{X}$-P control charts to obtain goal control limits. Studies have shown that the point estimator of the $C_p index, $C_p, could vary from time to time due to the sampling error. The suggested approach is to use confidence intervals, especially the lower confidence intervals, to replace the point estimator. Therefore, an improvement on target costing technique is presented by applying the lower confidence interval of the $C_p index and using both Taguchi and Spiring's loss functions together with $\bar{X}$-P charts to make this technique more robust in practice. An example is also provided to illustrate how the improved target costing technique works.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.9
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• pp.1139-1150
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• 1999

The evolution of silica aggregate particles in coflow diffusion flames has been studied experimentally using light scattering and thermophoretic sampling techniques. The measurements of scattering cross section from $90^{\circ}$ light scattering have been utilized to calculate the aggregate number density and volume fraction using with combination of measuring the particle size and morphology through the localized sampling and a TEM image analysis. Aggregate or particle number densities and volume fractions were calculated using Rayleigh-Debye-Gans and Mie theory for fractal aggregates and spherical particles, respectively. Of particular interests are the effects of flame temperature on the evolution of silica aggregate particles. As the flow rate of $H_2$ increases, the primary particle diameters of silica aggregates have been first decreased, but, further increase of $H_2$ flow rate causes the diameter of primary particles to increase and for sufficiently larger flow rates, the fractal aggregates finally become spherical particles. The variation of primary particle size along the upward jet centerline and the effect of burner configuration have also been studied.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.12
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• pp.67-73
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• 2015

This paper presents a fully integrated 3 - 5 GHz IR-UWB(impulse radio ultra-wide band) RFIC for Location based system. The receiver architecture adopts the energy detection method and for high speed sampling, the equivalent time sampling technique using the integrated DLL(delay locked loop) and 4 bit ADC. The digitally synthesized UWB impulse generator with low power consumption is also designed. The designed IR-UWB RFIC is implemented on $0.18{\mu}m$ CMOS technology. The receiver's sensitivity is -85.7 dBm and the current consumption of receiver and transmitter is 32 mA and 25.5 mA respectively at 1.8 V supply.

• Advances in environmental research
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• v.6 no.3
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• pp.229-240
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• 2017

This paper assessed environmental sanitation behaviour of market operators in selected markets in Ibadan, Nigeria. The two largest markets in the study area (Aleshinloye and Bodija markets) were selected for sampling. The selected markets represented the two types of markets; modern and traditional markets. The modern market comprises 3803 shops while the traditional market comprises 5943 shops. Multistage sampling technique was adopted in questionnaire administration. The selected markets were stratified into zones based on the goods sold. Systematic sampling was used in the selection of traders across the markets. 2% of traders were selected for sampling in each category of goods sold making a total of 189 respondents. This comprises 77 of traders from modern market and 112 traders from traditional markets. Descriptive and Inferential statistics were used in analysing the data. Findings revealed poor access to environmental sanitation facilities especially at the traditional market. The study also established poor environmental sanitation behaviour in terms of utilisation of available amenities across both markets. It recommended a synergy of efforts by all environmentally concerned institutions in managing the market environment. It also advocated for the provision of environmental sanitation facilities in markets by, government, market management authorities, traders, Community Based Organizations (CBOs) and Non-governmental Organizations (NGOs). In addition environmental education is imperative while enforcement of environmental regulations in the market and others with similar setting is strongly encouraged.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.53-58
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• 2007

OFDM (orthogonal frequency division multiplexing) is an effective modulation technique for high speed transmission over fading channels. However, it has a high bit error rate in the receiver if there is an error on frame synchronization because of phase rotation. A coherent OFDM system has to acquire exact timing synchronization of fraction and integer sampling positions. When a sampling offset exist the performance of a receiver will be degraded severely. In this paper, we propose an algorithm that acquires the fractional sampling offset in OFDM systems. This scheme compares the channel impulse responses with the early and late sampled signals having 0.5 sample offset from the estimated sampling positions by correlation with the received and training samples. Its performance is verified by computer simulations in multipath channels.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.872-878
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• 2013

In industrial control systems, flow measurement is a very important issue. It is frequently needed to calculate how much total fluid or gas flows through a cross-section. Flow volume measurement tools use simple sampling or rectangle methods. Actually, flow volume measurement process is an integration process. For this reason, measurement systems using instantaneous sampling technique cause considerably high errors. In order to make more accurate flow measurement, numerical integration methods should be used. Literally, for numerical integration method, Rectangular, Trapezoidal, Simpson, Romberg and Gaussian Quadrature methods are suggested. Among these methods, trapezoidal rule method is quite easy to calculate and is notably more accurate and contains no restrictive conditions. Therefore, it is especially convenient for the portable flow volume measurement systems. In this study, the volume measurement of air which is flowing through a cross-section is achieved by using PLC ladder diagram. The measurements are done using two different approaches. Trapezoidal rule method is proposed to measure the flow sensor signal to minimize measurement errors due to the classical sampling method as a different approach. It is concluded that the trapezoidal rule method is more effective than the classical sampling.

• Current Optics and Photonics
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• v.5 no.4
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• pp.409-420
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• 2021

We propose a method to synthesize a color non-hogel-based computer-generated-hologram (CGH) from light field data of a three-dimensional scene with a hologram pixel pitch shared for all color channels. The non-hogel-based CGH technique generates a continuous wavefront with arbitrary carrier wave from given light field data by interpreting the ray angle in the light field to the spatial frequency of the plane wavefront. The relation between ray angle and spatial frequency is, however, dependent on the wavelength, which leads to different spatial frequency sampling grid in the light field data, resulting in color aberrations in the hologram reconstruction. The proposed method sets a hologram pixel pitch common to all color channels such that the smallest blue diffraction angle covers the field of view of the light field. Then a spatial frequency sampling grid common to all color channels is established by interpolating the light field with the spatial frequency range of the blue wavelength and the sampling interval of the red wavelength. The common hologram pixel pitch and light field spatial frequency sampling grid ensure the synthesis of a color hologram without any color aberrations in the hologram reconstructions, or any loss of information contained in the light field. The proposed method is successfully verified using color light field data of various test or natural 3D scenes.

• International conference on construction engineering and project management
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• 2020.12a
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• pp.409-416
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• 2020

This paper proposes a study measuring productivity improvement by using a type of technology called "Machine Guidance" through work sampling in earthwork. Earthwork is the activity typically on the critical path, indicating that productivity for the activity is critical for managing schedule on time. Thanks to the development of sensing and information system technologies, productivity for earthwork has been improved. While there have been many studies investigating the application of a certain type of technology to earthwork, few studies have measured the productivity improvement and presented how the technology leads to productivity improvement. Based on the thorough literature review, it is hypothesized that Machine Guidance contributes to improving productivity of earthwork by reducing indirect workhours spent for information waiting and inspection. In addition to the literature review, this paper presents a research model to test the hypothesis by using the work sampling technique. By proving and quantifying the productivity improvement from the technology use, this study can help practitioners justify the investment for technology use, which will contribute to the deployment of technology and more effective execution of earthwork.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.339-342
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• 2000

Repetitive Load Prediction is proposed for the UPS inverter application of the second order deadbeat controller which is robust against the calculation time delay and the parameter variation and which gets fast response against the load variation. The proposed technique predicts the load current ahead of two sampling time using that the load current is periodic. This is effective under nonlinear load condition. The proposed technique is derived theoretically and verified through simulation and experimental result.