• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.11
• /
• pp.67-73
• /
• 2001

This paper aims at developing a torque model for the high-speed tapping with small-diameter taps. As recent industries such as automobile and information technology grows, taps smaller than 5mm in diameter are needed much more. In that occasion, the friction force between a tap surface and a workpiece plays much more important role in the tapping torque than in he larger tapping. Tapping mechanism was analysed based on the tap geometry. It has two steps : one is a forward cutting composed of the chamfered threading and full threading and the other is the backward cutting. The torque by the cutting force in the chamfered threading is calculated using the cutting area and the specific cutting force while the torque by the friction force, which is rather dominant than the cutting force both in the full threading and in the backward cutting, is calculated using the normal force on the threads and the friction coefficient. The experiment has shown that the results by the proposed torque model fit quite well with the acutal measurements within the error of 10%.

• Journal of Internet Computing and Services
• /
• v.6 no.2
• /
• pp.37-47
• /
• 2005

Most of the methods of estimating the size of software are based on the functions provided to costumers and in the process of granting the score to each function we consider the complexity during the process. The FFP technique has advantages applied to vast areas like data management. real-time system, algorithmic software, etc, but on the other hand, has disadvantage on estimating sizes for weights for necessary function elements. This paper proposes the estimating method for software size by considering the complexity of each function elements in full function point calculation method applied to a new developed project and maintenance projects. For this, based on function point by using surveyed data proved the validity of proposed method. The valid result. was that the function elements, the attributes used in size estimation of software, est mated better estimated sizes than in the case of other weights being applied.

• International Journal of Control, Automation, and Systems
• /
• v.6 no.4
• /
• pp.477-487
• /
• 2008

This paper proposes a new position sensorless drive for brushless DC (BLDC) motors. Typical sensorless control methods such as the scheme with the back-EMF detection method show high performance only at a high speed range because the magnitude of the back-EMF is dependent upon the rotor speed. This paper presents a new solution that estimates the rotor position by using an unknown input observer over a full speed range. In the proposed method, a trapezoidal back-EMF is modelled as an unknown input and the proposed unknown input observer estimating a line-to-line back-EMF in real time makes it possible to detect the rotor position. In particular, this observer has high performance at a low speed range in that the information of a rotor position is calculated independently of the rotor speed without an additional circuit or complicated operation process. Simulations and experiments have been carried out for the verification of the proposed control scheme.

• IEIE Transactions on Smart Processing and Computing
• /
• v.4 no.6
• /
• pp.384-390
• /
• 2015

There are two main artifacts in reconstructed images from in-beam positron emission tomography (PET). Unlike generic PET, in-beam PET uses the annihilation photons that occur during heavy ion therapy. Therefore, the geometry of in-beam PET is not a full ring, but a partial ring that has one or two openings around the rings in order for the hadrons to arrive at the tumor without prevention of detector blocks. This causes truncation in the projection data due to an absence of detector modules in the openings. The other is a ring artifact caused by the gaps between detector modules also found in generic PET. To sum up, in-beam PET has two kinds of gap: openings for hadrons, and gaps between the modules. We acquired three types of simulation results from a PET system: full-ring, C-ring and dual head. In this study, we aim to compensate for the artifacts that come from the two types of gap. In the case of truncation, we propose a method that uses prior knowledge of the location where annihilations occur, and we applied the discrete-cosine transform (DCT) gap-filling method proposed by Tuna et al. for inter-detector gap.

• Korean Journal of Community Nutrition
• /
• v.4 no.4
• /
• pp.489-495
• /
• 1999

This study was conducted to investigate the weaning practice of 198 infants in Taejon city in October, 1998. Information on infant feeding and weaning practices were obtained by interviewing mothers in gynecologist and pediatric clinics located in Taejon. The results obtained were as follows : In the survey 37.4% of the infants were breast-feeding, while 31.3% of them were bottle-feeding and 29.3% of them were mixed-feeding. The reason for bottled-feeding was due either to the lack of breast-milk secretion or motner’s job. The educational level of the mother and maternal job affected the feeding methods before weaning. Lower rates of breast-feeding were found among mothers witn a lover level of education. The breast-feeding rate was lower in full-time and part-time job worker groups than in housewife. There was no significant difference in the feeding methods according to family income. Among the subjects, 71.5% of infants began to be weaned within 7 months. The onset of weaning was delayed in the full-time worker group. There was no significant difference in the onset time of weaning according to feeding method, the educational level of the mother, and family income. 60.6% of infants received fruit juice and 29.6% of them received cereals for first-given-supplementary food. ‘For baby’s nutritional status’ was the most common motivation for the onset of weaning. Commercially prepared foods were used more than home-made food for supplementary food.

• Journal of Environmental Health Sciences
• /
• v.45 no.6
• /
• pp.569-576
• /
• 2019

Objectives: The main purpose of this study was to assess firefighters' daily personal noise exposure and explore noise levels related to specific tasks and their contributions to total noise exposure using 24-hour full-shift noise exposure measurements with task-based data. Methods: Noise exposure was assessed for eight firefighters (two rescuers, two drivers, and four suppressors) using time-activity diaries. We collected a total of 24 full-shift personal noise sample sets (three samples per a firefighter). The 24-hour shift-adjusted daily personal noise exposure level (L_ep,d), eight weekly personal noise exposures (L_eq,w), and 40 task-specific L_eq values (L_{eq activity}) were calculated via the ISO/NIOSH method. Results: The firefighter noise-sample datasets showed that most firefighters are exposed to noise levels above EU recommended levels at a low-action value. The highest noise exposure was for rescuers, followed by drivers and suppressors. Noise measurements with time-at-task information revealed that 82.3% of noise exposure occurred when checking equipment and responding to fire or emergency calls. Conclusions: The results indicate that firefighters are at risk of noise-induced hearing loss. Therefore, efforts at noise-control are necessary for their protection. This task-specific noise exposure assessment also shows that protective measures should be focused on certain tasks, such as checking and testing equipment.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.27 no.11
• /
• pp.126-134
• /
• 1990

In order to implement high-speed data acquistion system in CMOS VLSI technology, means must be found to overcome the relatively low transconductance and large device mismatch characteristic of MOS device. Because of these device limitations, circuit design approaches tradition-ally used in high-speed bipolar analog-to-digital converter(ADC) are suited to CMOS implementation. Also the design of VLSI CMOS comparator wherein voltage comparision is accomplished by means of a pipelined cascade RSA (Regenerative Sense Amplifier). So, in this paper we designed the A/D converter incorporates the pipelined CMOS comparator.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.35S no.7
• /
• pp.86-94
• /
• 1998

The rosette-scan seeker is a device mounted on the infrared guided missile. It offers the positions and iamges of target to missiles servo system by scanning a space about target in rosette pattern with a single detector. An instantaneous field of view (IFOV), which is a diameter of a detector moving along the path of the rosette pattern, has the property that its smaller size provide the less interference of background signals and detector noise. If its size is too small to voer the total field of view (TFOV), however, it produces the invisible regions in the TFOV. In this case, the invisible regions cause the performance of the seeker to deteriorate. For full scan-coverage, it is necessary to design the small IFOV without the invisible regions in the TFOV, as possible. In this paper, we propose the new method of designing the smaller IFOV than the conventional method and verify full coverage of the scanned region. By comparing the nose equivalent flux density (NEFD) of the proposed method with the that of the conventional one, we confirm that the former is better than the latter in terms of performance.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.6
• /
• pp.25-30
• /
• 2009

In this paper, a full-digital capacitive sensor for touch key applications is proposed. The proposed circuit consists of two capacitive loads to measure and a resistor between the capacitive loads. As the method measures the delays of the resistor and two capacitive loads respectively, and obtains difference between the capacitive loads by subtracting the two delays, it can reduce the effects of changing of operating environment variables such as supplying voltage, temperature and humidity. Experimental results show the method has l.02pF resolution and can be applied to touch key applications.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.3
• /
• pp.43-48
• /
• 2000

In this paper, vortical integrated transformers using bondwires are proposed and characterized for MMIC's (Monolithic Microwave Integrated Circuits) In a wide range of frequencies (1∼20 GHz), where full-wave analysis by the FEM (Finite Element Method) was adopted. The electrical characteristics of the proposed transformers are compared with those of the spiral transformer. We extracted mutual inductances from S -parameters. The vertical transformers using bondwires have not only low insertion loss but also reduce parasitic capacitances and dielectric loss due to their separation from substrates. It can be fabricated easily by used of the modern automatic wirebonding technology. It is expected that the proposed transformers are to improve the performance of MMIC's applied to impedance matching, and phase shifting circuits.