• International Journal of Highway Engineering
• /
• v.17 no.3
• /
• pp.1-12
• /
• 2015

PURPOSES : This paper presents a description of the current issues facing road managers regarding the surface-type conversion of low-volume roads for cost savings. METHODS: The paper reviews previous works conducted toward this end, acknowledges gaps in the current research, and lays out what information is needed for further studies. RESULTS : If the cost to maintain an unsurfaced road is less than the cost of maintaining a surfaced road, then there is potential for cost savings for the management agency. However, the problem is bigger than simply maintaining the roads that already exist. If unsurfaced roads prove to be more economical than surfaced roads, then the cost to convert from a surfaced to an unsurfaced roadway, and vice versa, when necessary, must also be examined. CONCLUSIONS : No other studies have addressed the un-surfacing of a road for cost savings, and it is therefore unknown whether substantial savings can be realistically obtained by converting from a surfaced to an unsurfaced road. To determine whether a conversion policy would be a viable option, additional data and research are needed.

• ETRI Journal
• /
• v.40 no.5
• /
• pp.664-676
• /
• 2018

Given the rapidly increasing market penetration of photovoltaic (PV) systems in many fields, including construction and housing, the effective maintenance of PV systems through remote monitoring at the panel level has attracted attention to quickly detect faults that cause reductions in yearly PV energy production, and which can reduce the whole-life cost. A key point of PV monitoring at the panel level is cost-effectiveness, as the installation of the massive PV panels that comprise PV systems is showing rapid growth in the market. This paper proposes an implementation method that involves the use of a panel-level wireless PV monitoring module (WPMM), and which assesses the cost-effectiveness of this approach. To maximize the cost-effectiveness, the designed WPMM uses a voltage-divider scheme for voltage metering and a shunt-resistor scheme for current metering. In addition, the proposed method offsets the effect of element errors by extracting calibration parameters. Furthermore, a design method is presented for portable and user-friendly PV monitoring, and demonstration results using a commercial 30-kW PV system are described.

• ETRI Journal
• /
• v.43 no.3
• /
• pp.459-470
• /
• 2021

This paper presents a low-cost prototype for monitoring online the maximum power produced by a domestic photovoltaic (PV) system using Internet of Things (IoT) technology. The most common tracking algorithms (P&O, InCond, HC, VSS InCond, and FL) were first simulated using MATLAB/Simulink and then implemented in a low-cost microcontroller (Arduino). The current, voltage, load current, load voltage, power at the maximum power point, duty cycle, module temperature, and in-plane solar irradiance are monitored. Using IoT technology, users can check in real time the change in power produced by their installation anywhere and anytime without additional effort or cost. The designed prototype is suitable for domestic PV applications, particularly at remote sites. It can also help users check online whether any abnormality has happened in their system based simply on the variation in the produced maximum power. Experimental results show that the system performs well. Moreover, the prototype is easy to implement, low in cost, saves time, and minimizes human effort. The developed monitoring system could be extended by integrating fault detection and diagnosis algorithms.

• Progress in Superconductivity and Cryogenics
• /
• v.25 no.4
• /
• pp.75-80
• /
• 2023

Rare earth barium copper oxide (REBCO) materials have shown the possibility of high-temperature superconductor (HTS) magnetic resonance imaging (MRI) magnets due to their elevated transition temperature. While numerous MRI magnet designs have emerged, there is a growing emphasis on estimating the cost before manufacturing. In this paper, we propose two designs of REBCO whole-body MRI magnets: (1) 1.5 T and (2) 3.0 T, the standard center field choices for hospital use, and compare their costs based on conductor usage. The basis topology of the design method is based on discretized solenoids to enhance field homogeneity. Magnetic stress calculation is done to further prove the mechanical feasibility of their construction. Multi-width winding technique and outer notch structure are used to improve critical current characteristic. We apply consistent constraints for current margins, sizes, and field homogeneities to ensure an equal cost comparison. A graph is plotted to show the cost increase with magnetic flux growth. Additionally, we compare our designs to two additional MRI magnet designs from other publications with respect to the cost and magnetic flux, and present the linear relationship between them.

• Korea Journal of Hospital Management
• /
• v.14 no.3
• /
• pp.23-48
• /
• 2009

The purpose of this study was to provide criteria which help executives to make decisions through the analysis of profitability of ultrasonography conducted in each medical department. In order to achieve such purpose, the study conducted break-even analyses on three medical departments of a university hospital in which has used ultrasonography was largely conducted in diagnosing diseases and performing surgeries. The research was carried out from January to June 2008. The data necessary for calculating cost, were collected using by computerized data. The results of the study were summarized as follows. 1. The Cost structure of each medical department: The Cost of ultrasonography was divided into direct cost and indirect cost through the categorization by cost object. Labor cost accounted for the largest portion of the direct cost with 69.3% in the department of obstetrics and gynecology, 67.4% in the department of radiology and 58.2% in the cardiac ultrasonography center, which followed by the depreciation cost of ultrasonography equipment. The calculation of the average material cost of each ultrasonographic test by medical test found that the cardiac ultrasonography center took first place with 2,355 won, followed by the department of obstetrics and gynecology with 266 won and the department of radiology with 233 won. As for the power cost of ultrasonography equipment, the department of radiology took fist place with 442,000 won. The power cost, however, did not affect much the cost price, because it accounted for only a small portion of the cost. As for indirect cost, the cardiac ultrasonography center ranked first with 7,156,000 won. Building depreciation cost accounted for the largest portion of the indirect cost. 2. Break-even analysis: Under the supposition that cost price can be divided into fixed cost and variable cost, a break-even analysis was conducted using the cost price confirmed through the cost structure of each medical department. As for the average customary charge of ultrasonography test conducted in each medical department, the department of obstetrics and gynecology charged 24,627 won, the department of radiology 53,179 won and the cardiac ultrasonography center 65,174 won. According to these results, the charges of ultrasonography test imposed by the department of radiology and the cardiac ultrasonography center wre enough to surpass break-even levels, but the charge imposed by the department of obstetrics and gynecology was not enough to offset the cost price. In conclusion, labor cost accounted for the largest proportion of cost price of ultrasonography test conducted in diagnosing diseases and performing surgeries in medical departments, followed by the fixed cost of ultrasonographic equipment depreciation cost. In medical department where the current charge of ultrasonography test turned out not to offset cost price through the break-even analysis of ultrasonographic equipment, ways to reduce fixed cost which accounts for the largest proportion of the cost price should be sought. Even medical departments whose current charge of ultrasonography test is enough to surpass break-even level are required to work for efficient management and cost reduction to continuously generate profits.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.2
• /
• pp.122-129
• /
• 2015

In this study, we propose a low voltage stress and cost-effective light emitting diode (LED) driver capable of multi-channel current balancing. Conventional LED drivers require as many boost converters as the number of LED channels, whereas the proposed LED driver requires only one buck converter and several balancing capacitors instead of several expensive boost converters. Additionally, while the components of the boost converter have high voltage stress and depend on the LED driving voltage, components of the proposed driver have about one-half of the voltage stress across all components. The proposed driver exhibits high reliability and cost effectiveness because it only uses few DC blocking capacitors with no additional active devices to balance the current of multi-channel LEDs. The proposed driver exhibits high reliability and cost effectiveness. The validity of the proposed driver is confirmed through a theoretical analysis. An explanation of the design considerations and experimental results were obtained using a prototype applicable to a 46" LED-TV.

• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.723-727
• /
• 2004

A new high-performance and low cost single switch energy recovery display driver for an AC plasma display panel (PDP) is proposed. Since it is composed of only one auxiliary power switch, two small inductors, and eight diodes compared with the conventional circuit consisting of four auxiliary power switches, two small inductors, eight power diodes, and two external capacitors, it features a much simpler structure and lower cost. Nevertheless, since the rootmean-square (RMS) value of the inductor current is very small, it also has very desirable advantages such as n low conduction loss and high efficiency. Furthermore, there are no serious voltage-drops caused by the large gas-discharge current with the aid of the discharge current compensation, which can also greatly reduce the current flowing through power switches and maintain the panel to light at n lower sustaining voltage. In addition, all main power switches are turned on under the zero-voltage switching (ZVS) and thus, the proposed circuit has a improved EMI, increased reliability, and high efficiency. Therefore, the proposed circuit will be well suited to the wall hanging PDP TV. To confirm the validity of the proposed circuit, circuit operations, features,and design considerations are presented and verified experimentally on a 6-inch PDP, 50kHz-switching frequency, and sustaining voltage 141V based prototype.

• Journal of Power Electronics
• /
• v.17 no.1
• /
• pp.76-87
• /
• 2017

Finite-set predictive current control (FS-PCC) is advantageous for power converters due to its high dynamic performance and has received increasing interest in multilevel inverters. Among multilevel inverter topologies, the cascaded H-bridge (CHB) inverter is popular and mature in the industry. However, a main drawback of FS-PCC is its large computational burden, especially for the application of CHB inverters. In this paper, an FS-PCC method based on a deadbeat solution for three-phase zero-common-mode-voltage CHB inverters is proposed. In the proposed method, an inverse model of the load is utilized to calculate the reference voltage based on the reference current. In addition, a cost function is directly expressed in the terms of the voltage errors. An optimal control actuation is selected by minimizing the cost function. In the proposed method, only three instead of all of the control actuations are used for the calculations in one sampling period. This leads to a significant reduction in computations. The proposed method is tested on a three-phase 5-level CHB inverter. Simulation and experimental results show a very similar and comparable control performance from the proposed method compared with the traditional FS-PCC method which evaluates the cost function for all of the control actuations.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2020.06a
• /
• pp.155-156
• /
• 2020

Unlike new construction projects, road paving maintenance work shows large productivity discrepancies depending on the conditions of the worksite. The current construction cost calculation scheme, however, only provides daily construction volume categorized by work scope and scale: There are no detailed standards that can be implemented on various types of worksites. To develop standards that enable the calculation of appropriate construction costs by taking into account worksite conditions, the current study conducted on-site surveys and interviews. The on-site research and analysis revealed that location, construction width, the day's worksite lot, work scope, and construction objectives were found to cause differences in construction volume. In addition to the existing work scope and work scape variables, the current study added weight constants reflecting the daily work volume based on movement conditions at site and the size of the worksite lot. In this process, the current study found that even one type of construction project can have fifteen different levels of daily construction volume. Such detailed classification was deemed to enable the proper calculation of construction costs based on worksite conditions.

• Journal of the Korean Dietetic Association
• /
• v.9 no.3
• /
• pp.197-208
• /
• 2003

This study was surveyed to provide the information on current operational practices and issues of contract-managed foodservice companies. Questionnaires were distributed to 79 contract-managed foodservice companies (eight large-size, 48 mid-size, 23 small-size companies) from March to May in 2002. The contract-managed foodservice companies provided averages of 269,184 (range 140,036-503,500), 14,837 (range 450-75,269), and 4,065 (range 930-8,050) meals daily from large, medium, and small-size companies, respectively. The companies managed to averages of 268.2 (160-619) foodservice contracts at large-size companies, 21.9 (5-63) contracts at mid-size companies, and 4.7 (1-10) contracts at small-size companies. The average numbers of dietitians were 298.6 (range 104-671) in large-size companies, 22.2(6-86) in mid-size companies, and 3.8(1-9) in small-size companies. The averages of sales were 156.5 billion at large-size companies, 6.7 billion at mid-size companies, and 1.7 billion at small-size companies in 2001. The contract was two types including management fee contract(5%), and profit and loss contract(95%). The cost ratios for office foodservice were 59.5% at food cost, 24.2% at labor cost, 6.3% at profit, and 10.1% at other cost. For hospital foodservice, the ratios were 54.0% at the food cost, 34.6% at labor cost, 3.0% at profit, and 11.8% at other cost. For high school foodservice, the ratios were 62.2% at the food cost, 21.5% at labor cost, 5.4% at profit, and 11.2% at other cost. When the contractors managed to the foodservice, the most important matters were the sanitation management and customer satisfaction. Also, the difficult problems were excess investment of equipments and low meal prices.