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In der Fachliteratur und den Fachgesellschaften existieren keine verbindlichen didaktischen Empfehlungen bzw. Richtlinien zur Gestaltung chirurgischer Trainingskurse. Die fortbildenden Institutionen planen, organisieren und evaluieren in Eigeninitiative ihre Bildungsprogramme und -veranstaltungen. In den Kursen eines Bildungsanbieters wurden im Rahmen eines Forschungsprojekts mit einer padagogisch-wissenschaftlich arbeitenden Forschergruppe strukturierte Beobachtungen, Expertendiskussionen mit Kursverantwortlichen und Trainern sowie Auswertungen von Teilnehmerfragebogen durchgefuhrt. Erste Masnahmen wurden installiert und umgehend in den Prozess der fortlaufenden Evaluation einbezogen. Aus der Evaluation ergaben sich konkrete Veranderungen im organisatorischen und mikrodidaktischen Bereich, die schnellstmoglich eingebunden wurden. Des Weiteren ergaben sich langerfristig zu bearbeitende Aufgaben in den Bereichen (a) Rollenverstandnis des Trainers, (b) Feedback geben respektive Leistung bewerten und (c) Inhalte differenziert aufbereiten. Fur Fortbildungsveranstalter in der Medizin ist eine langerfristige Zusammenarbeit mit einer begleitenden padagogisch tatigen Institution nicht nur moglich sondern empfehlenswert.

Diese Arbeit stellt ein neuartiges Trainingskonzept fur die Felsenbeinchirurgie auf der Basis von Gips-Kunstoff-Modellen mit optoelektrischer Detektion von Risikostrukturen vor und evaluiert es prototypisch. Grundlage der Trainingsmodelle sind hochauflosende CT-Datensatze eines humanen Schadels. Der Datensatz wird an einem 3D-Drucker ausgedruckt. Aus Gipspulver und einem Bindemittel wird das dreidimensionale Phantom erstellt. Als Risikostrukturen wurden der N. facialis, der Labyrinthblock, die Ossikelkette, der Sinus sigmoideus, die Dura und die A. carotis interna definiert. Als Detektionsmaterialien fur die Risikostrukturen werden eine elektrisch leitfahige Metalllegierung und ein Lichtwellenleiter verwendet. 8 unerfahrene und 8 efahrene Ohrchirurgen trainierten an den optoelektrischen Trainingssystemen (Gruppe A) und auserdem an humanen Felsenbeinpraparaten (Gruppe B). Bei Verletzungen werden Anzahl, Zeitpunkt, Grad (N. facialis) und verletzte Struktur, auserdem die benotigte Gesamtzeit werden wahrend des Trainings am Modell protokolliert. Die Auswertung der anatomischen Detailtreue der Felsenbeinmodelle zeigte Ergebnisse zwischen 49,5% und 90% Ubereinstimmung. Die Fehlerdetektion wurde mit Werten zwischen 79% und 100% Ubereinstimmung mit der Wahrnehmung eines erfahrenen Chirurgen bewertet. Das Op.-Setting wurde besser gegenuber dem Frasen am humanen Felsenbeinpraparat eingeschatzt. Die Probanden bejahten die Moglichkeit, die bisherige Trainingsmethode am humanen Felsenbeinpraparat vollstandig durch das Training am untersuchten Modell zu ersetzen. Die vorliegenden Daten belegen die Eignung des hier untersuchten neuartigen Trainingssystems fur die Felsenbeinchirurgie. Das System verbindet die Vorarbeiten mit gedruckten und gesinterten Modellen mit den Moglichkeiten der Mikrosystemtechnik. Daruber hinaus ist eine vollstandige virtuelle Darstellung des Modells mit den entsprechenden weiterfuhrenden Anwendungen („look behind the wall“, virtuelle Endoskopie) moglich.

Software application frameworks provide a modular and reusable context for the development of custom applications, e.g. in the domain of medical image processing and computer assisted surgery (CAS). The utilization of an appropriate software framework can strongly reduce time and costs for software design, implementation, and validation. However, the decision to apply a particular framework poses many risks that can have an impact on the success of the overall software project. There is a need for a software framework evaluation methodology that guides the selection process in an objective, impartial, and repeatable manner. This work defines an evaluation process for the selection of software application frameworks out of a group of candidates that fit best to defined requirements necessary for the development of CAS applications.

Hintergrund Die „Funktionelle Endoskopische Nasennebenhohlenoperation“ (FESS) ist durch eine einhandige Praparation und die Fuhrung des Endoskops mit der nichtdominanten Hand gekennzeichnet. Daraus ergeben sich eine Verlangerung der Operationszeit von bis zu 15% und ergonomische Defizite fur den Chirurgen. Das Ziel der vorliegenden Arbeit ist die Fortfuhrung der Konzeption eines automatisierten Assistenzsystems fur die Endoskopfuhrung bei der FESS. Dabei stehen folgende Fragen im Mittelpunkt: 1. Welches Design ist fur eine teilautomatisierte Endoskopfuhrung bei der FESS geeignet? 2. Wie sind die technischen Systemeigenschaften (Planung, Zeitaufwand, Genauigkeit, Prazision) des gewahlten Systems? 3. Bietet das System Potenzial fur eine klinische Anwendung?

Background The aim of this study was to evaluate the Navibase navigation system for ear, nose, and throat (ENT) surgery. A new methodology for evaluating surgical and human factors is developed. Patients and methods The evaluation is based on 102 ENT surgical applications, including 89 cases of functional endoscopic sinus surgery (FESS). The evaluation of surgical and human factors was performed by seven ENT surgeons. To evaluate surgical performance, level of quality (LOQ) in the 89 cases of FESS was determined, comparing the surgeon's own impressions with those of the navigation system on a scale from 0 to 100 and further comparing them with clinical results. Intraoperative changes in surgical strategy were documented. The human factors of total confidence (trust), situation awareness, skill set requirement and workload shift were recorded as level of reliance (LOR). Results The maximum deviation amounted to 1.93 mm. Averaging the quality of information resulted in an LOQ of 63.59. Every second application of the navigation system (47.9%) led to a change in surgical strategy. Total confidence showed a positive evaluation of 3.35 points in LOR. Conclusion Application-relevant information relevant to the application beyond only technical details permits comparison with other assisting systems.

Background: The feasibility of a navigate-controlled Shaver for the paranasal sinus surgery was proven in an initial study. Deficits showed up in the conversion of the planed cavity. Goal of this study is (1) the development and evaluation of a FESS demonstrator for the investigations to the surgical accuracy and (2) the evaluation of the resulting surgical accuracy for registration and conversion of the work space with an improved rigidity of the Shaver and a completely revised study design. Methods: As a demonstrator for the navigate-controlled resection of a volume through the Shaver a two-piece plastic head with an anatomical head and soft tissue model was designed. The investigation of the surgical accuracy takes place with 417 measurements to 4 different fiducial markers on the demonstrator head. The measurements for the deviation of the resulting cavity from the planned volume was realised with a work space by 24 x 24 × 30 mm. The 5 walls of the cavity were seized with 80 measuring points for each level and thus altogether 2000 measured values (5 models × 5 levels × 200 points). Results: The described demonstrator showed itself suitable for the close-to-application attempts to the surgical accuracy. The maximum deviation A max indicated position of the Shaver from the reference value amounted to 1,93 mm. The maximum average value of the exceeding of a planned cavity amounts to 1,62 mm. Conclusions: Based on these results a virtual safety passage of 2.00 mm is sufficient. The study refers the clinical serviceability of the navigate-controlled Shaver in paranasal sinus surgery.

Die Genauigkeit von Navigationssystemen stellt das herausragende Kriterium fur die Evaluation von Navigationssystemen dar. Die Angaben zur Genauigkeit variieren erheblich, und es besteht eine Diskrepanz zwischen Literaturangaben und der intraoperativen Genauigkeit. Es existiert kein einheitliches Verstandnis fur die Begriffe Genauigkeit und Prazision von Navigationssystemen, falschlicherweise werden diese auch gleichbedeutend verwendet. Daruber hinaus ist die klinische Genauigkeit nicht mit der technischen Bestimmung gleichzusetzen. Die vorliegende Arbeit hat das Ziel, den Begriff Genauigkeit und verwandte Begriffe grundlegend zu definieren, den Begriff der Prazision abzugrenzen, den Begriff chirurgische Genauigkeit abzuleiten, einen Vorschlag fur die Anwendung des Begriffs der chirurgischen Genauigkeit eines Navigationssystems zu unterbreiten, die vorhandenen Literaturangaben entsprechend einzuordnen. Dafur kamen die Normen nach der International Standardisation Organisation-ISO und dem Deutschen Institut fur Normung e.V.-DIN zur Anwendung.

In the Special Research Centre 414 of the German Research Funding (DFG, Bonn) a system for robot-assisted cranial surgery was developed. It is designed for the accurate and safe execution of craniotomies and repositioning of bone pieces. The system is intended for use in the surgical therapy of craniosynostosis. Preoperatively, CT imaging is performed. In a computerized planning system the position and shape of the intended craniotomy is intuitively planned on a virtual model of the patient's skull. Intraoperatively, after conventional removal of the covering soft tissue, the robot performs the craniotomy autonomously. Extensive testing in phantom studies and animal tests confirmed the reliability and accuracy of the system. A thorough risk analysis of the system was performed. In this paper, the first clinical use of the system on a patient is described and the clinical importance is discussed.

The use of surgical robots and manipulators is still being frequently discussed in the mass media as well as in the scientific community. Although it was already noted in 1985 that the first patient was treated by a joint team of robot and surgeon, today such systems are not routinely used. This can be explained by the high complexity of such systems and the often limited usability, but also, that it is difficult for surgeons to accept "automatic" machines. In this paper the possibilities and chances of robots and manipulators will be explained and it will be shown that robots will never work alone in the operating theatre as it is common in industry today. On the other hand, also limitations and challenges will be outlined. Therefore first a review on today's systems is given in different disciplines including oral- and cranio-maxillofacial surgery, then advantages and disadvantages are shown.

Design for Six Sigma (DFSS) is a product development process that uses metrics, data, statistics, and project management tools. The goal of Design for Six Sigma is that the new product should have robust performance. DFSS can be incorporated into an organization’s existing product development process and should involve taking products all the way from concept to commercialization. The follow paper describes the sensor developing process of the company arteos GmbH / Germany. In the presentation we give more DFSS-details and show a case study of sensor developing with DFSS.

In literature and scientific societies no binding methodical-didactic recommendations or guidelines exist in order to design surgical training courses. The educating institutions plan, organise and evaluate the educational program on their own initiative.Through a research project surgical training courses were investigated through structured surveys, expert discussions with course responsibles and trainers and analysis of participant's questionnaires. The investigation was performed by an pedagogical-psychological research institution. First implementations were installed and immediately included in the running process of evaluation.From the evaluation, specific alterations in the organisational and micro didactic process were implemented. In addition, changes in a long term process had to be implemented such as: (a) conception of the trainer role, (b) giving feedback and judge performance and (c) provide contents in a sophisticated manner.For advanced medical training providers a long term cooperation with a pedagogical institution seems to be highly advisable.

This work presents a new training concept for surgery of the temporal bone. It is based on a model of gypsum plastic with optoelectric detection of risk structures. A prototypical evaluation is given.The training models are based on high-resolution computed tomographic data of a human skull. The resulting data set was printed by a three-dimensional (3D) printer. A 3D phantom is created from gypsum powder and a bonding agent. Risks structures are the facial nerve, semicircular canal, cochlea, ossicular chain, sigmoid sinus, dura, and internal carotid artery. An electrically conductive metal (Wood's metal) and a fiber-optic cable were used as detection materials for the risk structures. For evaluating the training system, a study was done with eight inexperienced and eight experienced ear surgeons. They were asked to perform temporal bone surgery using two identical training models (group A). In group B, the same surgeons underwent surgical training with human cadavers. In the case of injuries, the number, point in time, degree (facial nerve), and injured structure were documented during the training on the model. In addition, the total time needed was noted.The training systems could be used in all cases. Evaluation of the anatomic accuracy of the models showed results that were between 49.5% and 90% agreement with the anatomic origin. Error detection was evaluated with values between 79% and 100% agreement with the perception of an experienced surgeon. The operating setting was estimated to be better than the previous"gold standard." The possibility of completely replacing the previous training method, which uses cadavers, with the examined training model was affirmed.This study shows that the examined system fulfills the conditions for a new training concept for temporal bone surgery. The system connects the preliminary work with printed and sintered models with the possibilities of microsystem engineering. In addition, the model's digital database permits a complete virtual representation of the model with appropriate further applications ("look behind the wall," virtual endoscopy).

Current advise systems in surgery use standard colors to communicate specific messages. Unfortunately, these colors may have a poor contrast to the background, like red on blood rich backgrounds of an OR microscope intervention. In this work, we present an approach of choosing high contrast colors based on the current image content, which is used in a study for an AR-based mode display of an active computer assisted surgery system.

In this paper, part of the invited session - Automation in medicine, the different effects of automation to the surgeon are discussed, including positive and negative consequences. One approach to analyze effects of automation is explained, and exemplarily shown on a study of the mode error at the computer assisted surgery (CAS) system navigated control.

The aim of this work was the evaluation of a navigated and power controlled milling system for spine surgery (navigated control spine). The navigation is based on a set of intraoperatively taken fluoroscopic images from different angles. A manually planned workspace limits the power of the mill and assures a higher automatisation degree than any other established navigation system for spine surgery.Both a technical study in workspace planning from fluoroscopic images and a milling study on a spine phantom were performed with participants with different level of knowledge of spinal surgery.In the region of interest the workspace planning could be performed with a maximum excess of 1.40 mm for surgeons. In the study performing the milling of a standardised workspace the remnant bone after milling had a mean difference from the planned workspace margin of 1.96-2.12 mm in the region of most interest. Accurate handling of the mill still required a certain level of medical knowledge and experience. In both studies the time needed for application of the system proved acceptable for clinical purposes.This concept of navigated and power controlled spinal surgery has proven feasible in an experimental study. This navigation system seems therefore promising for clinical application.

Intraoperative Bildgebung im Rahmen der minimal invasiven Chirurgie an der Wirbelsaule nimmt einen zunehmenden Stellenwert ein. Deswegen war es Ziel der vorliegenden Studie Arbeitraumplanungen durch 2D-Bilder des C-Bogens mit der Segmentierungen von analogen CT-Datensatzen zu evaluieren. An unterschiedlich erfahrenen Chirurgen wurde Genauigkeit und Zeitaufwand der Segmentierung an einem Wirbelsaulenphantom analysiert. Insgesamt war die CT-Segmentierung der 2D-Segmentierung uberlegen. Jedoch zeigte sich, dass bei Einhalten eines Sicherheitsabstandes von 1,5mm die 2D-Segmentierung mittels aufgenommener Bilder eines C-Bogens eine hinreichende Genauigkeit in der klinischen Praxis zulasst. Der durchschnittliche Zeitaufwand fur die intraoperative Segmentierun ist mit ca. 3 Minuten fur den Alltagsgebrauch vertretbar. Eine Lernkurve wurde bei allen unterschiedlich erfahrenen Chirurgen verifiziert.

Patients who are treated with a mastoidectomy usually suffer from an inflammation of the petrosal bone. The intervention is a time consuming landmark based surgery and usually performed with a powered drill. Delicate risk structures must be respected. Navigated Control (NC) describes the control for a power driven instrument which is controlled by a surgeon and additionally controlled according to the position of the instrument relatively to a deliberated position known from a preoperatively segmented work space which excludes risk structures. The force of a drill can be regulated by the principle of NC. Following results were received: 1. Risk structure segmentation is feasible 2. The drill and a phantom can be registered. 3. With NC the resection is faster, more accurate and with no risk structures damage. 4. The phantom is suitable.

The Operating Room (OR) is more and more equipped with surgical assist systems which make use of modern image acquisition and processing technologies. Within this scenario, the surgeon has to deal with a large amount of information which must be available at the right time and in the right place. This results in various real-time problems which must be addressed while building surgical assist systems. The components of such systems and their real time requirements are presented in this paper. Several concrete systems are presented and their real time properties discussed.

Functional endoscopic sinus surgery (FESS) is characterized by single-handed preparation and guidance of the endoscope by the nondominant hand. This results in an additional extension of operation time by up to 15% and ergonomic deficits. The aim of this study is the conception of an automated assistance system for FESS in view of the following questions: (1) Which degree of surgical automation is suitable for FESS? (2) Which design is suitable? (3) What are the properties of the technical system (planning, time, accuracy, precision) of the selected system? (4) Does the system offer potential for a clinical application?In all 49 FESS were analyzed for surgical workflows. Measurement of the maximum forces within FESS was performed with 40 trials on an anatomical model. Three different mechanical systems were used in ten FESS and evaluated using the ICCAS Human-Machine Evaluation Scale. For realization of automated endoscope guidance an engine-driven and -braked manipulator (PA10-6c, Mitsubishi, Japan) was used. The technical parameters determined were expenditure of time for the preoperative planning of workspace, surgical accuracy and precision of the intraoperative endoscope positioning, maximal forces, and time.Concept-conditioned instrument changes amount to an average of 41.1 and 18.9% (5.21 min) time requirement for each FESS side. Maximum forces on the mucous membrane during a conventional FESS were measured at 9.8 N (5.9-9.8). Usability of the mechanical endoscope holder was estimated in 18 of 20 cases to be inferior to the standard procedure. The time needed for segmenting the intranasal workspace was 15.2 min (10.0-23.0). The maximum deviation of the automatically driven endoscope from a planned position amounted to 0.85 mm (manually 4.64 mm). The maximum force was measured with 1.1 N in the z direction (manually 9.8 N). Automated guidance of the endoscope to an intranasal position needed 7.25 s (6.4-7.9); manually 12.64 s (5.9-43.0).Guidance of the endoscope for FESS by an automated motor-driven system is possible. The conception which is based on workflow analysis favors a system with automatic definition of the workspace and a manual movement of the endoscope. The examined system offers a potential for clinical application. Definition of the automation level and development of a man-machine interface is more important than selection or reconstruction of a special manipulator for endoscope guidance in FESS from a surgical point of view.

The aim of this study was to evaluate the Navibase navigation system for ear, nose, and throat (ENT) surgery. A new methodology for evaluating surgical and human factors is developed.The evaluation is based on 102 ENT surgical applications, including 89 cases of functional endoscopic sinus surgery (FESS). The evaluation of surgical and human factors was performed by seven ENT surgeons. To evaluate surgical performance, level of quality (LOQ) in the 89 cases of FESS was determined, comparing the surgeon's own impressions with those of the navigation system on a scale from 0 to 100 and further comparing them with clinical results. Intraoperative changes in surgical strategy were documented. The human factors of total confidence (trust), situation awareness, skill set requirement and workload shift were recorded as level of reliance (LOR).The maximum deviation amounted to 1.93 mm. Averaging the quality of information resulted in an LOQ of 63.59. Every second application of the navigation system (47.9%) led to a change in surgical strategy. Total confidence showed a positive evaluation of 3.35 points in LOR.Application-relevant information relevant to the application beyond only technical details permits comparison with other assisting systems.

The feasibility of a navigate-controlled Shaver for the paranasal sinus surgery was proven in an initial study. Deficits showed up in the conversion of the planed cavity. Goal of this study is (1) the development and evaluation of a FESS demonstrator for the investigations to the surgical accuracy and (2) the evaluation of the resulting surgical accuracy for registration and conversion of the work space with an improved rigidity of the Shaver and a completely revised study design.As a demonstrator for the navigate-controlled resection of a volume through the Shaver a two-piece plastic head with an anatomical head and soft tissue model was designed. The investigation of the surgical accuracy takes place with 417 measurements to 4 different fiducial markers on the demonstrator head. The measurements for the deviation of the resulting cavity from the planned volume was realised with a work space by 24 x 24 x 30 mm. The 5 walls of the cavity were seized with 80 measuring points for each level and thus altogether 2000 measured values (5 models x 5 levels x 200 points).The described demonstrator showed itself suitable for the close-to-application attempts to the surgical accuracy. The maximum deviation A (max) indicated position of the Shaver from the reference value amounted to 1,93 mm. The maximum average value of the exceeding of a planned cavity amounts to 1,62 mm.Based on these results a virtual safety passage of 2.00 mm is sufficient. The study refers the clinical serviceability of the navigate-controlled Shaver in paranasal sinus surgery.

The aim of this study is the evaluation of a navigation system (NaviBase) for ENT surgery. For this purpose, a new methodology for the evaluation of surgical and ergonomic system properties has been developed. The practicability of the evaluation instruments will be examined using the example of the overall assessment of the system in comparison with the current surgical standard and with other systems using clinical efficiency criteria. The evaluation is based on 102 ENT surgical applications; of these, 89 were functional endoscopic sinus surgeries (FESS). The evaluation of surgical and ergonomic performance factors was performed by seven ENT surgeons. To evaluate surgical system properties, the Level of Quality (LOQ) in 89 cases of the FESS was determined. It compares the existing information of the surgeon with that of the navigation system on a scale of 0 to 100 and with a mean value of 50 and places it in a relationship to the clinical impact. The intraoperative change of the planned surgical strategy (Change of Surgical Strategy) was documented. The ergonomic factors of the system with the categories of Overall Confidence (Trust), awareness of the situation (Situation Awareness), influence on the operating team, requirements for specific skills (Skill Set Requirement), and cognitive load (Workload Shift) were recorded for all surgical procedures as Level of Reliance (LOR). In the evaluation of the surgical system properties, an average evaluation of the quality of the information, as an LOQ of 63.59, resulted. Every second application of the navigation system (47.9%), on average, led to a change in the surgical strategy. An extension/enhancement of the indication of the endonasal approach through the use of the navigation system was shown in 7 of 102 (6.8%) cases. The completion of the resection in the FESS was rated by 74% of group I and 11% of group II as better in comparison with the standard approach. Total confidence shows a positive evaluation of 3.35 in the LOR. To supplement the evaluation of the navigation system, the technical parameters were included. The maximum deviation, Amax, of the displayed position of the reference value amounted to 1.93 mm. The average deviation was at 1.29 mm with an SD above all values, sd, of 0.29. The subsequent economic evaluation resulted in an effective average extra expenditure of time of 1.35 minutes per case. The overall evaluation of the system imparts application-relevant information beyond the technical details and permits comparability between different assistance systems.

Navigated Control (NC) describes an additional control for a tracked power driven instrument within a preoperatively segmented work space. In head surgery the authors first implemented NC in functional endoscopic sinus surgery (FESS). Recently the feasibility of NC for surgery on the petrosal bone is evaluated. NC in FESS and in petrosal bone surgery may reduce the risk of comorbidity and the time effort compared to the conventional surgical interventions.

Accuracy represents the outstanding criterion for navigation systems. Surgeons have noticed a great discrepancy between the values from the literature and system specifications on one hand, and intraoperative accuracy on the other. A unitary understanding for the term accuracy does not exist in clinical practice. Furthermore, an incorrect equality for the terms precision and accuracy can be found in the literature. On top of this, clinical accuracy differs from mechanical (technical) accuracy. From a clinical point of view, we had to deal with remarkably many different terms all describing accuracy. This study has the goals of: 1. Defining "accuracy" and related terms, 2. Differentiating between "precision" and "accuracy", 3. Deriving the term "surgical accuracy", 4. Recommending use of the the term "surgical accuracy" for a navigation system. To a great extent, definitions were applied from the International Standardisation Organisation-ISO and the norm from the Deutsches Institut für Normung e.V.-DIN (the German Institute for Standardization). For defining surgical accuracy, the terms reference value, expectation, accuracy and precision are of major interest. Surgical accuracy should indicate the maximum values for the deviation between test results and the reference value (true value) A(max), and additionally indicate precision P(surg). As a basis for measurements, a standardized technical model was used. Coordinates of the model were acquired by CT. To determine statistically and reality relevant results for head surgery, 50 measurements with an accuracy of 50, 75, 100 and 150 mm from the centre of the registration geometry are adequate. In the future, we recommend labeling the system's overall performance with the following specifications: maximum accuracy deviation A(max), precision P and information on the measurement method. This could be displayed on a seal of quality.

A prominent boost-type 3-level topology, which is proved to represent a cost effective and highly efficient solution for switched mode rectifiers is inspected towards its application at wide input voltage range and power line distorted conditions including single-phase supply. Supplementary measures for a low cost control scheme are described to facilitate the operation under these unfavorable conditions. Shutdown of e.g. telecommunication plants can thus be avoided, if a maximum power limitation is observed. The inherent adaptation of the control scheme to the largely varying supply conditions supports the high yielding efficiency at high output voltage, even when supplied out of two phases. Simulation and measurement results prove the maturity of this rectifier scheme.

A prominent boost-type three-level topology, which proved to represent a cost effective and highly efficient solution for switched mode rectifiers is inspected towards its operation at discontinuous conduction mode (DCM). This mode of operation occurs not only at high input voltage in conjunction with low load currents but even at medium loading in the vicinity of mains voltage zero crossings. Since the requirements on THD conflict with the actual behavior of the circuit when operated at DCM, measures are needed for optimization. After reviewing basic measures to avoid DCM the resemblance to three-phase/single-switch boost rectifiers is utilized to control the circuit. Novel measures to optimize the modulation scheme are proposed, facilitating the design of even smaller inductors, thus lowering costs. Selected simulation and measurement results prove the enhanced modulation scheme.

Different methods are known for giving all the solutions to the inverse kinematics problem for general serial-link manipulators. One of these is Raghavan and Roth’s algebraic algorithm. An eigenvalue problem based on this, which is numerically robust, was formulated by various authors. Practical implementation requires algebraic precomputation, because the underlying equations are computationally involved. This can be done by “computer algebra systems” (CAS). We show here a notational concept that avoids the use of CAS. Therefore the algorithm can be implemented on every personal computer by every programming language; even for those who have no access to CAS. But even more importantly, the solution process is much faster.

Ti‐doped GaAs crystals grown by the liquid‐encapsulated Czochralski method were investigated by using the observation of direct capacitance transients. The charge transfer transitions to the deep Ti donor level close to midgap are unambiguously identified in both n‐type and p‐type material. The energy position of Ti3+/Ti4+ is determined with high precision of Ec−(0.87±0.01) eV at 300 K and the respective cross sections are σn∞=(7±3)×10−15 cm2 for electron capture and σp∞=(10±5)×10−16 cm2 for hole capture. The position of the Ti2+/Ti3+ acceptor is confirmed to be at Ec−(0.19±0.01) eV. Its cross section for electron capture is σn∞=(3±1)×10−16 cm2.

Semi‐insulating In0.53Ga0.47As with carrier concentration n=1.2×1012 cm−3, resistivity up to 1090 Ω cm, and mobility up to 9500 cm2/V s at 300 K is grown by liquid‐phase epitaxy and doping with Fe. The influence of Fe doping on the photoluminescence of In0.53Ga0.47As is systematically investigated. An acceptor level at Ev+150 meV, tentatively assigned to Fe by some of us earlier, is definitively identified as an Fe‐related complex. This acceptor level, however, is not responsible for the semi‐insulating behavior of In0.53Ga0.47As as shown by statistical calculations. High‐resolution deep‐level transient spectroscopy experiments show two deep acceptors at EC−ET=0.44 and 0.30 eV, respectively. The first one, which dominates, is identified as being caused by the Fe3+/Fe2+ acceptor level. The second, somewhat weaker one, might be caused by the O‐related trap recently discovered by Loualiche et al. [Appl. Phys. Lett. 51, 1361 (1987).] Combining the Fe acceptor energy position in In0.53Ga0.47As with its known v...

Tunnel diode I‐V, dI/dV, and d2I/dV2 characteristics are used to examine defect effects and phonon energies in In1−xGaxP1−zAsz double‐heterojunction lasers (λ‐1.1 μm) grown by liquid‐phase epitaxy on InP substrates. Similar to the usual conductance minimum observed at zero bias, a conductance minimum in the dI/dV characteristics is observed at small forward bias (40⩽V⩽60 meV) and is identified as two‐step tunneling (via defects) to Zn‐acceptor states on the p‐type side of the junction. An increase in the conductance is observed below the region of carrier injection and is attributed to tunneling from residual acceptor states on the n‐type side of the junction. Fine structure in the dI/dV and d2I/dV2 characteristics permits the identification of optical phonon energies at two In1−xGaxP1−zAsz compositions (x=0.12, z=0.26; x=0.16, z=0.35) and in this region indicates two‐mode behavior for the quaternary alloy.

A system for measuring I‐V, dI/dV, and d2I/dV2 characteristics of two‐terminal devices is described. An operational amplifier integrator is used to produce a sweep voltage. For derivative measurements the dc bias voltage is modulated by a constant ac voltage signal. Current is detected by a near‐zero input impedance circuit with adjustable gain. A simple circuit utilizing an IGFET at zero drain voltage as a voltage controlled resistor compensates for harmonic content in the oscillator signal. It also enhances the detectability of weak harmonic signals in the presence of a strong fundamental signal by rejecting more than 90% of the strong signal. The system has been used to measure devices with impedances from a few ohms to over 105 Ω.

Stimulated emission in AlGaAsP is demonstrated. Double heterojunction AlGaAsP lasers grown from Ga solution on GaAsP substrates exhibit 300 °K thresholds as low as 104 A/cm2 (∼ 8450 A) and shift ∼ 450 A to shorter wavelength at 77 °K. In spite of its more complicated crystalline structure, solution‐grown AlGaAsP appears to exceed in quality vapor‐grown GaAsP.

Measurements have been made at 4.2°K on p-n tunnel junctions in the mixed crystal systems In 1− χ Ga x P. Large excess currents and zero bias conductance minima indicate a high concentration of defects in the junctions, which are fabricated on Zn-doped substrates. As the composition changes from InP to GaP, a single k ≅ 0 phonon mode is observed at energies near the top of the InP optical phonon band, which becomes the LO phonon mode in GaP.

Growth of Ti‐doped In0.53Ga0.47As using liquid phase epitaxy is reported. The energy position of the Ti4+/Ti3+ deep donor level in In0.53Ga0.47As p‐n diodes is precisely identified for the first time by deep level transient spectroscopy. The near midgap location of this level at EC−ET =0.37 eV and the potential of InGaAs:Ti of superior thermal stability make it a promising dopant for growing semi‐insulating In0.53Ga0.47As. A recent model suggesting the energy positions of transition metals not to vary across heterojunctions is tested and found to be at least qualitatively valid for this low spin transition metal.

Defect‐assisted (’’two‐step’’) tunneling is observed in the I‐V and dI/dV characteristics of LPE In1−xGaxP1−zAsz double‐heterojunction laser diodes (Jth∼4.7×102 A/cm2, λ∼1.05 μm, 77 °K). The change in conductance (’’turn‐off’’) at zero bias due to resonant‐elastic tunneling, and a related change at 40–60 mV involving acceptor states, are compared with similar data on Zn‐diffused InxGa1−xAs laser diodes, and indicate that the Zn dopant in either type of laser diode is the main source of the defects involved in the two‐step tunneling.

The multilayer circuit board offers many advantages in electronic design, particularly for packaging of semiconductor integrated circuits and other microelectronic elements for spacecraft systems. Essentially a multilayer circuit board is a stack of printed circuit (etched wiring) boards forming a matrix with all interconnecting wiring prefabricated and built in. To determine multilayer circuit design requirements, the problems presented by an existing space electronic assembly were analyzed in detail. Redesign, using multilayer circuits and microelectronic parts, resulted in a 15-to-1 reduction in the volume of the package. Consideration was given to layout and spacing, use of miniature mounting posts, fabrication methods, electrical test and checkout, repair and servicing, part-connection techniques, and environmental resistance. A feasibility demonstration model of an electroplated five-layer circuit board was constructed experimentally. Based upon the design problems presented by this unit, practical standards for multilayer circuits have been evolved.

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