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There have been more than necessary casualties due to a lack of intelligence in emergency evacuation mechanisms such as exit signs. Although large or complex buildings and facilities have many exit doors, in case of emergency, people may not be able to escape quickly enough due to sudden loss of directions and difficulty in finding safe routes to exit doors. If you were ever in such a situation, you would wish that if there were ever smart escape route assistance mechanisms available or at least smart exit signs available that safely and quickly guide you to a safe haven. It is what we try to make such a wish come true. In this paper, we propose a graph mapping scheme and a new safe evacuation route algorithm for safe emergency evacuation assistance, with the aid of recent technology called Internet of Things (IoT). The gist of our approach is that people are not allowed to pass through or even go towards any area where fire or toxic gas is detected by controlling the direction signals installed on exit signs. The experiments performed with our methodology shows that the proposed technology may be able to save more lives.

In the Internet of Things, tremendous data is generated by huge number of things and stored in globally distributed data repositories. In this respect, many IoT applications would need to find and get the data indirectly from the data repositories or directly from things. GS1, global leading standard organization, firstly presents the concept of Discovery Service (DS) to find the desired EPC Information Services (EPCIS) like data repositories for things. To realize GS1 DS, many works are proposed with considerations of performance and security issues. However, most works are only applied to the Inter-DS finding one of distributed Intra-DSes; thus deterioration in the Intra-DS actually finding desired data repositories may adversely affect entire DS. In this paper, we propose Oliot-Discovery Service (DS) which deals with performance as well as security issues by especially focusing on Intra-DS aspect. For this, we have designed and implemented the access control pursuing the fine-grained access control model and the two-layered storage architecture comprised of cache and main databases. Moreover, it supports not only indirect access to things' data through the data repositories but also direct access to things which would be also required for many IoT applications. In order to show feasibility of Oliot-DS, we have constructed experimental test-bed and evaluated the performance. The experiment results show that Oliot-DS provides durability against many user transactions, and the reasonable write and read performances by preventing unauthorized access.

Software-defined networking (SDN) is under consideration for deployment of carrier-grade networks (CGN). SDN must meet the critical network reliability requirement without incurring high complexity and network resource usage. Local detouring of disrupted flows from the failed network component to a preconfigured alternative path enables rapid recovery. Preconfigured alternate paths reduce the recovery time, however, result in storing thousands of flow entries per switch. Furthermore, the reliance on the controller for per-flow detouring would overwhelm the controller and increases the recovery time. To address these issues, we propose a proactive recovery scheme to repair an OpenFlow-based network from a node or a link failure without overburdening the controller and the flow tables memory. The proactive scheme aggregates the disrupted flows using virtual Local area network (VLAN) tagging to conserve the flow table memory requirement. A fast failover (FF) feature of OpenFlow is used to perform rapid local detouring. Our extensive simulation results reveal that the proposed scheme achieves the recovery around 4 ms and satisfies the CGN's 50 ms recovery requirement. Additionally, the proactive recovery scheme reduces the alternate path flow storage requirement by up to 99%.

Fourth generation 1200V field stop trench IGBT technology has been developed to have better trade-off performance compared to the previous second generation field stop trench IGBT technology. This new technology achieved 25% smaller switching-off power loss and 0.1V lower Vce(sat) as well. These improvements are key features demanded by industrial applications for higher power density and better system efficiency. The device characteristics and performance in target applications are evaluated.

The revolutionary improvements in low power devices and lightweight network protocols are making the mobile healthcare engage attentions. However there are some obstacles to realize mobile healthcare. Connectivity of miniaturized wearable sensors of the body area network (BAN) to the Internet is one of the most important issues in realizing mobile healthcare system. Interoperability is also important in order for sensor data not to be isolated in a local system. In this paper, we designed our mobile healthcare system resolving connectivity and interoperability issues. In our mobile healthcare system, body sensors are integrated by leveraging RESTful web service via CoAP over IPv6, enabling web-based access from browsers. Extended EPCglobal architecture was used for our system to enable sharing of sensor data among applications with different domain through the standardized protocol. We developed two applications, patient browser and EagleEye, to prove its feasibility.

Message broadcasting is an essential and widely-used operation in multi-hop Wireless Sensor Networks (WSNs). Minimum latency broadcast scheduling (MLBS) aims to achieve a schedule to broadcast messages with a minimum latency. In duty-cycle networks, a node alternates between active and sleep states, which causes decrease in energy consumption at the cost of increased broadcast latency. An existing scheme mathematically remodels the MLBS problem for duty-cycled WSNs and proposes a vector integration algorithm to solve the problem. In this paper, we propose a broadcast scheduling scheme by first finding critical-paths in a duty-cycled WSN. By scheduling transmissions with a preference of nodes in the critical-path, the proposed scheme reduces the broadcast latency as shown in the simulation results.

Recent innovation in mobile technologies has changed from the static architecture of client-server relationships toward dynamic, mobile, and instant networks. Accordingly, many studies have been done to support the seamless mobility networks. However it is difficult to deploy such networks due to the need of a special network infrastructure supporting mobility management. In this paper, we propose a novel mobility management scheme without depending on any essential network infrastructure. It establishes a direct tunnel between a Mobile Node (MN) and a Correspondent Node (CN) using virtual IP addressing. The assigned virtual IP addresses of MN and CN are fixed during their communication session via the tunnel. When MN is moving, the changes of its physical IP address are updated to CN by the Virtual Tunnels (VTUN) layer to keep their communication session. The performance evaluation results show that the proposed scheme significantly reduces the L3 handover latency compared with that of PMIPv6.

Smart home and Internet of Things (IoT) are recently drawing attention as the next-generation concept for home appliances. Inexpensive wireless communications technologies for connecting appliances to have enhanced capability and service will be important. This paper proposes the Inaudible Dual Tone Data transmission (IDTD) method, which can be applicable to them based on built-in speakers and microphones. IDTD utilizes an inaudible frequency band of 18kHz or higher in order to minimize discomfort for users. In order to prevent noise, each signal is allotted with dual tone. The proposed method is implemented using a speaker (BNM0026) which is actually applied to appliances. IDTD provides a higher speed and success rate than the existing sound communication systems while keeping the transmission distance is same. This results show feasibility of the data transmission at home appliances without extra hardware.

High swell is often generated offshore and damages the east coasts of Korea and accidents, a correct prediction of dangerous swells should be done before they approach to the shore. Recently, a warning system to countermeasure dangerous swells is setup on the east coast of Korea with simultaneous in-situ wave measurements at the northeast site of Ulleung offshore island and at Hupo nearshore station. By analyzing these intensive wave observation data and wave prediction model results, detailed swell characteristics are studied in the East coast of Korea. Calculated wave data by the system are compared to the wave data predicted using wind input data and observed wave data at nearshore station.

Fast handover for Proxy Mobile IPv6 (FPMIPv6), a protocol described in RFC 5949, is used to resolve handover latency and packet loss problems that occur in the Proxy Mobile IPv6 (PMIPv6) protocol. However, while implementing the FPMIPv6 scheme in the testbed, we reveal the Out-of-Order Packet (OoOP) problem. We propose a new scheme using last packet marker and buffering to handle the OoOP problem in FPMIPv6, since the problem significantly affects QoS of the network and performance of the Mobile Node (MN). The cause of this problem is the existence of two paths for data transmitted from Correspondent Node (CN) to MN in FPMIPv6. The new Mobility Access Gateway (MAG) can control and deliver the data transmitted via the old path or the new path to MN in chronological order, using the last packet marker to notify the end of data delivery in the old path and the buffering for holding the data delivered in the new path. We implement both the proposed and FPMIPv6 schemes in a testbed as a real network environment to demonstrate the correctness, cost effectiveness, and performance of the proposed scheme. Performance evaluation reveals the proposed scheme can handle the OoOP problem efficiently.

Data aggregation is used to reduce the average number of transmissions and to save energy by aggregating multiple packets into a single packet in Wireless Sensor Networks (WSNs). Data aggregation scheduling problems have been extensively studied to make sure collision-free packet delivery to a sink node, with the goal of minimizing the aggregation time. Almost all existing data aggregation schemes have a continuous energy consumption problem of RF transceiver because they assume that each node is always in an active state. Recently, the data aggregation scheduling in duty-cycled WSNs is considered to reduce energy consumption. In this paper, we propose a delay-aware data aggregation scheduling scheme to minimize latency in duty-cycled WSNs. In a data aggregation tree construction phase, our proposed scheme constructs Connected Dominating Set (CDS) tree on the shortest path in terms of delay according to an active time slot of each node. The CDS tree is used as virtual backbone for efficient data aggregation. In a scheduling phase, the proposed scheme ensures collision-free data aggregation to the sink with reduced latency by considering data receiving time in each node. The simulation results show that comparing to related work, our proposed scheme can reduce the average time for data aggregation to the sink by 54% and 50% with various node densities and duty cycle respectively.

In this work we discuss, problems associated with aggregating data within a sensor network. Clearly, if one or more sensors are faulty, their data is questionable. In situations where data is aggregated together to form information, the accuracy of the information will also be questionable if some of the data is faulty. We briefly discuss some “simple statistical functions”, which may need to be computed using sensor data. We construct some approximation methods for aggregated statistical functions within a sensor network.

In this paper we explore several different quality assessment tests for images. The scenario is such that wireless sensors are transmitting images to a Base Station for processing purposes. For energy conservation purposes, the sensors would like to reduce bandwidth. Hence they get directions concerning overlap between images thereby allowing them to reduce transmissions. The problem that arises is the situation of false positives — i.e. the Base Station is saying there is overlap when in reality there is none. Thus some information must be periodically transmitted to the Base Station by the sensors in order to allow the Base Station to assess the quality of the image that is reconstructed. Here we discuss a number of different quality assessment test and provide results of some simulation experiments we have conducted on the different tests.

In the hybrid SAW-ED deposition system for conductive thin-layer, droplets generation depend upon the SAW. Also, the electrostatic field can help pull off the droplets to the substrates. In this paper, the efficiency of hybrid SAW-ED head is studied analytically. For the development of hybrid SAW-ED deposition system, the optimized parameters for conductive thin-layer can be ascertained from the results discussed here. The background of this research is to get micro droplets and successive spray and the optimal conditions for the development of conductive thin-layer needed for devices of printed electronics through hybrid SAW-ED deposition system.

In this paper, we design an observer-based stabilizing controller for a web transport system to asymptotically stabilize the full state. Our results are achieved by analyzing system dynamics in the following manner: we first review the Timoshenko model to describe the web between two rollers and the extension to a multi-roll system. Then, we show that the system is both stabilizable and detectable by examining the uncontrollable and unobservable modes. A simulation study is conducted to demonstrate the results of the controller and observer.

This study proposes and evaluates an average consensus scheme for wireless sensor networks. For this purpose, two communication error models, the fading model and random error model, are introduced and incorporated into the proposed decentralized average consensus scheme, especially adapted to the constraints of wireless sensor networks. Finally, different simulation scenarios are introduced and their results analyzed to evaluate the performance of the proposed scheme and its effectiveness in meeting the needs of wireless sensor networks.

In this paper, effect of cross-talk between the nozzles in triangular array multi-nozzle for electrohydrodynamic inkjet printing head is investigated on the basis of jetting angle i.e. deflection of meniscus at the boundary nozzles. By changing the process parameter i.e. flow rate of the liquid, applied voltage and space between the capillary nozzles; jetting angle at end capillaries are measured and analyzed. Experimental results show that, by keeping applied voltage constant and increasing the flow rate the jetting angle decreases. While keeping flow rate constant and increasing the applied voltage jetting angle increases. Moreover jetting angle increases with the decrease in space between the nozzles. To better evaluate this technique, electric field simulations are performed and compared with the experimental results. We observed a strong correlation between the simulated and experimental results.

In the paper, a mathematical model of roll printing pressure control system using the pneumatic system is proposed. By writing the system of dynamic equations in strict feedback form and applying the back-stepping theory, a full state feedback controller is obtained with gains that are determined optimally by modified genetic algorithm (MGA). A printing pressure control algorithm is given by using the proposed mathematical development and controller. The simulation results employed in Matlab/Simulink show the stability and high precision of the proposed algorithm.

Rapid manufacturing and high accuracy are very important factor in the Selective Laser Sintering (SLS) process, one of Solid Freeform Fabrication (SFF) system due to the life cycle of a product getting shorter. This paper addressed development of an industrial SFF system which employs the new laser scan path algorithm for more elaborate and speedy system for fabricating objects compared to existing SLS process. New laser scan path algorithm called Digital Mirror System (DMS). It contains variable beam expander for getting various laser beam spot size instead of the existing fixed beam expander. Also, experiments were performed to evaluate the effect of a new laser scanning path and fabrication parameters on sintering process and to fabricate the various 3D object using polymer power.

There have been growing interests in direct patterning of metallic contents on the surface of the substrate without including complex steps of the micro fabrication lithography process. The direct fabrication process using ink-jet printing can be expected to be a powerful tool for both nanotechnology research and applications such as micro electronics. The electrostatic inkjet system has a huge number of applications in terms of cost and time effected manufacturing of printed electronics like RFID, electronic devices and flexible display, solar cell, sensors etc. Inkjet printers operate by propelling various size droplets of conductive ink onto the non conductive substrate. For experimental purpose, an integrated electrostatic inkjet nozzle head was fabricated. For the charging of ink meniscus, an electrode is inserted inside the nozzle head containing conductive ink. The difference between the charge meniscus and ground electrode is depended on the ink properties like surface tension, viscosity and number of metallic pigments. Therefore, for the extraction of droplets, a ring type ground terminal with internal diameter of 1.5mm, 1mm. 0.5mm with a fixed distance of 500um from the meniscus is employed. The paper is focused on the different meniscus shape and extractions in meniscus before dripping is evaluated through experiments. And optimal ground is proposed. This study will help to develop and analysis the integrated electrostatic nozzle head and aspects of the nozzle head.

This paper introduces a newly improved MOSFET, Ultra-FRFET of which T rr characteristic is much faster than that of the typical MOSFET and presents its effectiveness when it is applied to HV-BLU system of LCD TVs. The reverse recovery time, T rr of Ultra-FRFET is shorter than 40 nsec and the peak value of reverse recovery current, i rr is also much smaller compared to the typical MOSFET's, which are sufficient to prevent the MOSFET's failures without additional FRDs and diodes in HV-BLU system with a half-bridge resonant inverter topology worked by PWM method. In order to verify the validity, the loss analysis and the experimental for both cases, the conventional solution using typical MOSFETs with additional FRDs and new soution using only Ultra-FRFETs are implemented for the HV-BLU of 40" LCD TV. As a result, the effectiveness of Ultra-FRFET was verified and the results are presented in this paper.

There are many important applications in printed electronics and publishing industries that use the principle of roll-to-roll manufacturing to make devices at high speeds with lower cost. Web velocity and tension control algorithm plays an important role in improving the quality of product in mass processing of using roll-to-roll web technology. Most algorithms proposed in recent years use PI or PID controllers and disturbance compensation schemes to increase the precision and the stability. Due to the increasing demand of high accuracy in printed electronics industry at micrometer-level, it is necessary to have a precise control scheme of web velocity and tension in the presence of disturbances. In this paper, a precise control algorithm is proposed for non-linear single-span roll-to-roll web control system using the back-stepping controller with the design parameters chosen optimally by using the modified genetic algorithm. The outcome of this study proves the reliability throughout simulation results in Matlab/Simulink and comparison with the existing results employed by PI controllers.

This paper presents the electro-luminescence (EL) display lamp which is patterned on a curved surface by the pad printing method. The EL display lamp consists of 5 layers: Bottom electrode; Dielectric layer; Phosphor; Transparent electrode; Bus electrode. For proper pad printing, the ink of each layer was formulated and the pad printing condition was controlled. A PEN film was used first in order to realize the pad printing process condition of each layer. Finally, the EL display lamp was printed on a dish, which has a radius of curvature 80mm.

This paper proposes a high-speed single-chip eye tracker that eliminates the effect of the glint and generates the digital address for the center of the pupil.

Lab. simulator for conducting a performance test and a reliability test on a vehicle and components has been embodied. In order to control non-linear of a vehicle, a fuzzy control algorithm, a running mode tracking algorithm and a vehicle speed control algorithm were applied to the actuator control. The vehicle controller and servo controller functions were implemented; position control, the gear shift control depending upon the vehicle RPM, control with actuator by controlling the pneumatic servo valve, and measured data information such as a position, a velocity and an acceleration as obtained through operation by means of the second differentiator and controlled a position precisely. An experimental apparatus was consisted of a dynamometer and a vehicle, and the performance and durability of the controller was verified. The Lab. simulator was mounted onto the vehicle, and the position control test and a LAP mode tracking test were conducted. It was found that the response characteristic, the tracking capability and precision of the position control were so excellent.

Currently, SFF (solid freeform fabrication) technologies are being developed for diverse processes. 3DP (three-dimensional printing), one of these SFF technologies, confers the advantage of high-speed processing at low cost, since it makes use of multi-nozzle inkjet printing. However, it requires additional post-processing due to the additional drying time of the adhesive and the lower mechanical strength of the fabricated product. This paper proposes a novel 3DP process which can improve the slow solidification and post-processing by applying photopolymer resin and UV curing apparatus to the conventional 3DP process. To verify the feasibility of the proposed process, the mechanical strengths (tensile and bending), surface roughness, and dimensional errors of the specimen were compared with those of the conventional process. The result showed an improvement of the yield stress by 5 times and the dimensional accuracy in the z-axis by approx. 50%. Furthermore, the overall fabrication time (with the proposed novel 3DP process) was faster than the conventional process by approx. 200%, since the proposed method does not require any additional solidification time or post-processing due to the improvement in strength.

In this paper, we present high aspect ratio 3D metal micro column and 65deg-inclined micro column made by molten metal DoD inkjet system. A design, fabrication and performance test of the DoD metal-jet system are introduced for application to the molten metal such as lead free solder. In the experimental test, we set up the test apparatus for visualization of the droplet ejection and measure the ejected droplet volume and velocity. As a result, the diameter, volume and the velocity of the ejected droplet are about 65 -70 mum, 145 -180 pi and 4 m/sec. Finally, we can fabricate vertical and inclined 3D micro column structures using the molten metal inkjet system. The measured geometries of the micro column structures are about height of more than 2,100 mum, diameter of 200 mum and aspect ratio of 10.5 for vertical micro column and l,400 mum of height and 150 mum of diameter for 65deg-inclined micro column, respectively.

In Solid Freeform Fabrication System (SFFS), the reduction of total processing time is very important specifically for SLS process that is sintered using heat energy. When the time delay occurs in the process, shrinkage, warpage and curling occur by a heat energy distribution difference and effect the accuracy and the system efficiency. Therefore, the reduction of total processing time is an important issue in SFF system. A digital mirror system (DMS) is a system which scans the laser beam with different spot size. The spot size is selected based on the slicing section to decrease and accuracy of the process time and improve the processing efficiency. In this study, the optimal scan path generation for DMS will be addressed, and this development will improve the whole processing efficiency and accuracy through the scan efficiency by considering the existing scan path algorithm and heat energy distribution.

Polyamide 12 were studied as the laser sintering materials for the three-dimensional duplicator equipment of selective laser sintering process. Though polymer powders had a similar chemical structure, there were some differences in thermal properties, particle size and distribution, and shape. These variations had a close relation with the processibility of laser sintering. As far as the particle shape approached a spherical shape, the processibility was improved. The particle size distribution played an important role in the precision of fabrication. The polymer powders with uniform size and higher bulk density were successfully prepared by controlling several finely-controlled steps, such as dissolution, nucleation, propagation and crystallization, in wet process. Several additives were added to improve the thermal, rheological, and flow properties further.

Recently, study of 3D freeform fabrication method was working in the various applications. SFF (solid freeform fabrication) technologies are being developed for diverse processes. 3DP (three-dimensional printing), one of these SFF technologies, confers the advantage of high-speed processing at low cost, since it makes use of multi-nozzle inkjet printing. In this paper, we introduce a method of 3D freeform fabrication using a curing of photo-polymer resin and construct a system has multi printing head. A photo-polymer curing method has simply fabrication process and high strength of manufacturing part. We construct the printing system using multi piezo print head and it needs the heating system for lower the high viscosity of photo-polymer resin. In the result of experiment, printing system has not need the heating system because low viscosity photo-polymer resin is possible to jetting in the normal temperature. In the conclusion, we fabricate the 3D freeform part, which is suitable to the office environment using a photo-polymer curing method.

A solid freeform fabrication (SFF) system using selective laser sintering (SLS) is currently recognized as a leading process and SLS extends the application to machinery and automobiles due to the various materials employed. Especially, accuracy and processing time are very important factors when the desired shape is fabricated with selective laser sintering (SLS), one of solid freeform fabrication (SFF) system. In the conventional SLS process, laser spot size is fixed during laser exposing on the sliced figure. Therefore, it is difficult to accuracy and rapidly fabricates the desired shape. In this paper, to deal with those problems a SFF system having ability of changing spot size is developed. The system provides high accuracy and optimal processing time. Specifically, a variable beam expander is employed to adjust spot size for different figures on a sliced shape. Finally, design and performance estimation of the SFF system employing a variable beam expander are achieved and the mechanism will be addressed to measure the real spot size generated from the variable beam expander.

Selective laser sintering (SLS) is currently recognized as a leading process in the new field of solid freeform fabrication (SFF). In order to develop more elaborate and speedy system for fabricating large objects compared to existing SLS, this study employs digital mirror system (DMS) for selective laser sintering (SLS) process. DMS contains 3-axis dynamic focusing lens, zoom beam expander, x-y galvano mirror, reflection mirrors for scanning large area instead of the existing fthetas lens used in commercial SLS. Also, in the SLS, the sintering temperature, laser beam power and layer thickness have a great influence on sintering of the polymer. Experiments were performed to evaluate the effect of a scanning path and fabrication parameters on sintering process and to fabricate the various 3D objects using polymer

SFF system could quickly makes models and prototype parts from 3D computer-aided design (CAD) data. SFF system in the office environment is a tool that streamlines and expedites the product development process. The 3DP technology is one of SFF(solid freeform fabrication) technologies which have recently came into the spotlight and are being applied to various fields. This process has the advantage of the fast manufacture time. But conventional 3DP process needs the post-process necessarily and a part fabricated by this process has too low strength. So we proposed a new 3DP process to reduce post-process time and fabricate a part with high strength and construct a SFF system. In this study, we constructed the SFF system using a photopolymer resin and a powder. We used the piezo printhead for the printing of the UV resin on the slice contour and experimented the curing of photopolymer resin in the powder based 3DP system.

Solid freeform fabrication system (SFFS), which is one of rapid prototyping (RP) systems, has been widely used to fabricate 3D solid part by sintering powder and stacking the fabricated layer. To fabricate a part, a laser scan path as machining path is needed. The laser scan path has to be generated in consideration of fast and precise scan. In case of fabricating larger size parts, the unique scan device and scan path generation should be considered. In this paper, the development of SFFS machines being capable of large size fabrication, which is about 500times1000times800 mm (WtimesDtimesH) will be addressed. The dual laser system and the unique scan device have been designed and built, which employ CO2 lasers and dynamic 3-axis scanners. The developed system allows scanning a larger planar surface with the desired laser spot size. Also, to generate a dual laser scan path, a single laser scan path has to be divided into two parts with respect to the center of each layer. To evaluate the suggested method, the specimen will be fabricated

3DP (three dimensional printing) technology is one of SFF (solid freeform fabrication) technologies which have recently come into a spotlight due to its adaptability to various applications. This technology has a great advantage in terms of short fabrication time for a prototype at a low cost, especially when it comes with multi-nozzle inkjet printing technology. However, it has also a disadvantage since it requires additional curing time, after jetting a binder material, and post-processing time in order to increase the mechanical strength of a product. In this study, a novel 3DP process is proposed to overcome slow solidification and elaborate post-process by adopting photo curing method into the conventional 3DP process. Mechanical properties, such as tensile and bending strengths, of specimens fabricated with the proposed 3DP process were measured and compared with those fabricated with the conventional 3DP process. As a result, it is found that mechanical strengths of specimens from the proposed novel 3DP process show three times higher than those from the conventional 3DP process. Besides, the overall fabrication time with the proposed novel 3DP process is about two times faster than that with the conventional 3DP process, because it does not need additional curing and post-processing time

The problem min-power k-connectivity seeks a power assignment to the nodes in a given wireless ad hoc network such that the produced network topology is k-connected and the total power is the lowest. In this paper, we present several approximation algorithms for this problem. Specifically, we propose a 3k-approximation algorithm for any k /spl ges/ 3, a (k + 12H (k))-approximation algorithm for k(2k - 1) /spl les/ n where n is the network size, a (k + 2 [(k + 1)/2])-approximation algorithm for 2 /spl les/ k /spl les/ 7, a 6-approximation algorithm for k = 3, and a 9-approximation algorithm for k = 4.

This paper presents an algorithm to obtain the intersections of a free-form surface with a series of parallel planes. When sectioning the surface with parallel planes, the change of the topology of the intersection curves is caused by characteristic points of the surface. There are seven types of characteristic points: interior maximum, interior minimum, interior saddle, boundary maximum, boundary minimum, boundary max-saddle, and boundary min-saddle points. The starting points of the intersections are found efficiently and robustly using the characteristic points. The characteristic points as well as the intersection contours can be used to evaluate the machining information for process planning, to generate NC tool path for surfaces, and to generate slices for rapid prototyping.