The Combined Optimization of Log Bucking and Sawing Strategies

Determination of optimal bucking and sawing policies is linked in a common model. The core of this model is a linear program (LP) that selects stem bucking and log sawing policies to maximize profits given an input distribution of raw material. Product output is controlled by price-volume relationships that simulate product demand curves. The model uses a three stage solution process performed iteratively until identical solution bases are obtained. A variation of the Dantzig-Wolfe decomposition principle is used, linking the three models through the use of the Lagrange multipliers from the LP. The procedure is demonstrated for a sample sawmill. The revenue gain from using the policies suggested by the integrated model over those found by the bucking and sawing programs working separately was found to be 26%-36%

The Effect of Log Rotation On Value Recovery In Chip And Saw Sawmills

Advances in three-dimensional scanning techniques and computer optimization permit real time solution and implementation of optimal log rotation before it is fed into the chipper heads. A random sample of 834 S-P-F logs from the interior of British Columbia were examined using simulation to determine the effects of log rotation strategies on value recovery for a small log Chip and Saw. Both log sweep and cross-sectional eccentricity are shown to cause significant reductions in value recovery. Eight rotation placements from 0° to 315° were studied to determine if a single rotational placement could be found that performs best. On average, the "horns up" position (0° rotation) was found to significantly outperform all others in maximizing value recovery. The ability to rotate each log into the optimal position produced significant benefits. The benefits were more highly related to the degree of cross-sectional eccentricity present in the log rather than the degree of sweep present in the log

Reliability Testing of Statistical Process Control Procedures for Manufacturing with Multiple Sources of Variation

Quality inconsistencies can be caused by processes with multiple sources of variation. Therefore, the development of control charts that perform properly for both producer's and consumer's risk can be very complex. This is particularly true for real-time SPC systems that collect a great deal of data through noncontact sensing. In this paper, we demonstrate the use of a Monte Carlo simulation procedure that can be used to test SPC charts for both consumer's and producer's risk, and an experimental design procedure to analyze the results. This procedure is shown to be especially useful where design factors interact to cause high variation in a quality characteristic of a product. The approach is illustrated for a practical problem taken from the lumber manufacturing industry and demonstrates that commonly used industrial practices to control product dimensions lead to erroneous conclusions. To that end, a new mathematical approach that yields the correct results is described. The Simulation / ANOVA procedure described in this paper may have applicability in the control of many other industrial processes

SPC Methods for Detecting Simple Sawing Defects Using Real-Time Laser Range Sensor Data

Effective statistical process control (SPC) procedures can greatly enhance product value and yield in the lumber industry, ensuring accuracy and minimum waste. To this end, many mills are implementing automated real-time SPC with non-contact laser range sensors (LRS). These systems have, thus far, had only limited success because of frequent false alarms and have led to tolerances being set excessively wide and real problems being missed. Current SPC algorithms are based on manual sampling methods and, consequently, are not appropriate for the volume of data generated by real-time systems. The objective of this research was to establish a system for real-time LRS size control data for automated lumber manufacturing. An SPC system was developed that incorporated multi-sensor data, and new SPC charts were developed that went beyond traditional size control methods, simultaneously monitoring multiple surfaces and specifically targeting common sawing defects. In this paper, eleven candidate control charts were evaluated. Traditional X-bar and range charts are suggested, which were explicitly developed to take into account the components of variance in the model. Applying these methods will lead to process improvements for sawmills using automated quality control systems, so that machines producing defective material can be identified and prompt repairs made

Statistical Considerations for Real-Time Size Control Systems in Wood Products Manufacturing

Currently, sawmill machinery companies are developing real-time size lumber size control systems using non-contact laser measuring systems. These systems rely on the application of industrial statistics to large quantities of lumber thickness and width data. Because of the sampling intensity and frequent decision making in real-time systems, there is an increased chance of committing Type I or Type II errors when drawing conclusions if statistical methods are incorrectly applied. There is confusion in the industry concerning the appropriate statistical model to use for lumber size control. This survey of the current literature discusses three distinct methods for calculating and partitioning sawing variation, and thereby calculating control limits for control charts. This paper reviews the statistical foundation and current understanding of industrial statistics for implementing real-time SPC systems and makes recommendations for improvement

Production Planning for Integrated Primary and Secondary Lumber Manufacturing

This paper describes two linear programming models that were developed for production planning in value-added lumber manufacturing facilities. One model is designed for nonintegrated value-added facilities; the other is designed for value-added facilities integrated with a sawmill. The models were then used to explore the financial benefits for a sawmill to integrate a value-added lumber manufacturing facility at the back end of the mill. Net revenues are compared from the sawmill's point of view for two experimental cases. In Case 1 the sawmill sells its entire lumber production to the market (including to an independent value-added facility). In Case 2, the sawmill sells only the lumber that it is not directed to the value-added facility for further processing. Net revenue for Case 2 exceeds the net revenue of Case 1 by 10%. Results shown demonstrate that production decisions in the value-added facility had a significant influence on production decisions in the sawmill

Using flow simulation as a decision tool for improvements in sawmill productivity

We developed a sawmill fl ow simulation model to identify production bottlenecks and determine where productivity improvements could be made. Sawmills often invest in a new machine center and then find out that the processing bottleneck just moves somewhere else. Our approach was specifically designed to investigate the effects of such changes on the entire system. We determined that the trimmer was the system bottleneck when both the small log and large log lines were running concomitantly. Under base case conditions, the model predicted an average board output of 13,147 boards. An increase in the processing capability of the trimmer resulted in a shift of the bottleneck from the small log line to the large log line (at the edger). This bottleneck shift was further investigated and, by allowing the simulation model to manipulate machine settings for the trimmer and edger, it was able to maximize the modeled average board output to 17,996 boards per shift (when edger set up times were not considered) and 16,708 boards per shift (with edger setup times included). These findings were presented to the sawmill management and subsequently implemented as specific improvements at the trimmer machine center, which in turn resulted in an actual increase of 10% in their sawmill’s lumber volume output

Teaching in Contemporary Forest Resources Curricula: Applications to Courses in Forest Measurements and Biometrics

Foresters face new and evolving challenges as society reconsiders the balance of its interests between wood production and the provision of ecosystem services in the management of forests. Whatever paths this process may take, sound and broad-based decisions will continue to require accurate and relevant measurements of current forest conditions and projections of future conditions under alternative management programs. Forest measurements and biometrics (FMB) will remain a key component of future forest management and a critical element in the education of future forest managers. As professors who both teach and do research in FMB, we offer teaching goals that we believe will improve FMB education in forestry schools to meet future needs. In the following sections, we outline teaching goals for university-level instruction in forest resources curricula and the roles of FMB in modern forestry. We then identify what we feel are the most critical challenges in teaching and learning FMB and discuss selected strategies to meet teaching objectives for FMB. A fourth section presents an overview of how selected strategies can be integrated into FMB classes, including examples and comments on the role that new technology might play in meeting the above-described challenges. The final section summarizes our main points and provides concluding remarks.This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Society of American Foresters and can be found at: http://www.safnet.org/publications/jof/index.cfm.Keywords: forest inventory and monitoring, teaching applied statistics, Pacific Northwest, forest analysis, forest pedagog

AIDS virus–specific CD8+ T lymphocytes against an immunodominant cryptic epitope select for viral escape

Cryptic major histocompatibility complex class I epitopes have been detected in several pathogens, but their importance in the immune response to AIDS viruses remains unknown. Here, we show that Mamu-B*17+ simian immunodeficiency virus (SIV)mac239-infected rhesus macaques that spontaneously controlled viral replication consistently made strong CD8+ T lymphocyte (CD8-TL) responses against a cryptic epitope, RHLAFKCLW (cRW9). Importantly, cRW9-specific CD8-TL selected for viral variation in vivo and effectively suppressed SIV replication in vitro, suggesting that they might play a key role in the SIV-specific response. The discovery of an immunodominant CD8-TL response in elite controller macaques against a cryptic epitope suggests that the AIDS virus–specific cellular immune response is likely far more complex than is generally assumed

Miscarriage and stillbirth following maternal Zika virus infection in nonhuman primates.

Zika virus (ZIKV) infection is associated with congenital defects and pregnancy loss. Here, we found that 26% of nonhuman primates infected with Asian/American ZIKV in early gestation experienced fetal demise later in pregnancy despite showing few clinical signs of infection. Pregnancy loss due to asymptomatic ZIKV infection may therefore be a common but under-recognized adverse outcome related to maternal ZIKV infection