The International Drying Symposium series (IDS) was inaugurated in 1978 with the express objective of fostering international cooperation and providing a forum for university-industry interaction on a global scale. Starting from a modest meeting in Montreal, IDS has now matured into a major movement with its own momentum driven initially by the escalating energy costs and later by demands for higher quality products new processes and environmental implications. This paper will attempt to provide a capsule overview of the progress of the IDS series, its impact on worldwide drying R&D and its future. Some statistical information is also included for archival purposes.

The First International Symposium on Drying, its official title at the time, was announced in Spring 1977 and held in August 1978 on the campus of McGill University in Montreal, Canada. Fortunately, despite the short induction time it turned out to be a success, thanks to sponsorships by several large companies and several professional societies. A formal proceedings volume was published, it contained only about 40 papers although about twice as many were presented at the meeting. A Forum was held on R&D Needs and Opportunities which reflected strong industrial interest and accentuated the need for a forum devoted to exchange of information on drying regardless of geographical, disciplinary and industrial sectoral boundaries. Thus, the food or textile industry could benefit from advances made by the paper industry in drying of continuous sheets, for example. It was recognized that drying is a truly inter- and multi-disciplinary field that can only advance by sharing the expertise in different disciplines and industries. Indeed, there is no major industry that does not utilize drying processes at some stage of their manufacturing sequences.

The First International Symposium on Drying attracted 210 participants from 22 countries. About 90 papers were presented along with 6 Keynote lectures. Only about half of the papers presented appeared in the proceedings volume while most of the remainder appeared in Drying'80, volume 1. A Panel Discussion was organized on Needs and Opportunities in Drying to identify industrial needs and promote industry-university interaction on a global scale. One unique feature of the first symposium was the fact that it attracted a greater number of participants from industry rather than academia (112 from industry and government laboratories and 98 from academic institutions). It was clear that industry was well aware of its drying R&D needs while the academic world was not quite active in the field probably as a result of years of traditional isolation from the industrial environment. Without exception academic participation exceeded the industrial one in all later IDS meetings. I believe a balanced participation is the key to success in effective technology and knowledge transfer and IDS must endeavor to correct this anomaly in future.

Subsequent evolution of the IDS series, as indicated in Table 1, clearly shows the rising interest in drying R&D by both academia and industry on a truly global scale. Participation by industry demonstrated the need for better understanding of various drying processes and the numerous challenging problems in drying. The academic community benefited by being exposed to industry needs so that they could develop new viable research programs. Cross-fertilization of ideas occurred as participants from different disciplines, different countries and different industries inter-mingled and readily appreciated the commonality of several drying problems they had thought to be the exclusive domains of their discipline or industry. This awareness also helped develop research collaborations and avoid unnecessary duplication of research effort. Many vendors of drying equipment presented technical aspects of their new drying equipment although, in my view, it would be nice to see much more activity of this nature at IDS meetings. Many academic researchers have put forward truly innovative new concepts for dryer design that the vendors should try to commercialize.

Without significant industry participation there is a danger that academic researchers will follow what I call a "closed-loop" approach to research (see editorial in Drying Technology-An International Journal, 16(1&2), 1998). Basically it leads to academic research by academics and for academics. In an applied field such as drying results of research are wasted if they are not used by industry in some fashion. In the closed loop approach one academic paper spawns another and this sequence continues indefinitely until, perhaps, research funds run out. While this does lead to a larger citation frequency the results are typically wasted. What we really need to assess drying research (and indeed any other applied research) is a "utilization index" and not a citation index since only another academic can typically cite a published paper. I believe that IDS provides an opportunity for the academic to interact with the industry counterpart and familiarize himself/herself with real world problems awaiting effective solutions.

Statistically speaking, Figures 1 and 2 provide a quantitative insight into the development of drying research interest in general while Figures 3 and 4 focus on IDS'96 in particular. It is interesting to note in Figure 1 the contribution to drying literature as reflected in the number of papers published in the only archival journal solely devoted to drying technology viz. Drying Technology-An International Journal (Marcel Dekker, Inc., N.Y.). Contrary to expectation, the contribution level for the U.S.A. is on the same order as that for Canada. Several countries from Europe, e.g., France, Poland, Finland, etc., display a significantly larger R&D effort on per capita basis. It is well known that most of the well recognized drying equipment manufacturers are based in western Europe although they have operating subsidiaries or licensees in North America.

Figure 2 shows the significant and continuous rise in the number of papers published in Drying Technology-An International Journal since its inception in 1982. It is obvious that such a trend cannot be sustained and indeed the objective of the journal is to reduce the size of the volume by about 40% over the next few years which will increase both the selectivity and quality of the technical content even further.

I am delighted that Drying Technology-An International Journal is now available for personal subscription rate for just US$ 99 per annum - an incredible bargain for anyone even remotely interested in the field in industry or academia. The website at http://www.dekker.com provides more details. As the manuscript flow continues its unabated rise over the past decade the journal will be increasingly selective and raise its technical quality and value to the readership at large. One continuing difficulty faced by the editors is the relatively small pool of reviewers who volunteer their valuable time and energy to provide critical, constructive, incisive as well as evaluative reviews within a reasonable timeframe.

Figures 3 and 4 provide some statistical data for IDS'96. Figure 3 shows that agriculture and food setorsdominate the industrial topics covered while mathematical modeling and equipment related papers are a significant fraction of the total. Figure 4 confirms what has been obvious for a long time, western and eastern European contribution to drying R&D exceeds that from North America by almost an order-of- magnitude.

Figure 1. Research effort in drying by national origin based on paper published
in Drying Technology-An International Journal (1991-1997)

Figure 2. Number of pages published per volume in
Drying Technology-An International Journal (1983-1997)

Another noteworthy variation with IDS location and timing appears in the number of papers which focused on energy and related issues in drying, e.g., energy savings, alternative energy sources, heat recovery systems, use of heat pumps for drying, etc. In recent years there is a decline in the number of papers related to energy aspects while there is a corresponding rise in those dealing with quality aspects which are necessarily product-oriented. Since energy and environment are intertwined the interest in making drying more efficient will continue to rise. Combustion of fossil fuels used for drying inevitably leads to generation of greenhouse gases - a topic of considerable contemporary interest.

Figure 3. Papers presented at IDS'96 and fields of interest

Figure 4. Participants from different regions (IDS'96)

As expected the geographic location of the meeting has a strong bearing on the number of local participants, industrial sectors of interest as well as the total attendance. IDS'98 attracted a record 430 abstracts from some 57 countries breaking all previous records. The final attendance figure approached 350 from 55 countries. The 3- volume set of Proceedings, Drying'98, contains over 250 papers. I expect IDS'2000 in the Netherlands to be a major drawing card as well for obvious reasons. A greater industrial participation level is planned for that meeting.

It is difficult to make a clear-cut classification of the subject matter of various papers presented at IDS's. Any classification scheme one might propose has to be somewhat arbitrary and overlapping since a given paper may be classified into several categories simultaneously. Coumans (1997) classified the IDS'96 papers into three major categories as follows:

1. Theoretical (fundamentals, simulation, modeling, etc.): 23%
2. Practical (equipment-oriented, technology, control, etc.): 25% and
3. Product-based (e.g., those dealing with foods, agriculture paper, wood, etc.): 52%

Of the product-based papers some 60% of the papers dealt with food and agriculture. Drying of paper and wood were major topics only at IDS meetings held in North America and western Europe.

As far as industrial sectors are concerned, food and agriculture remain the most dominant sectors in view of the critical importance of drying to their industry- typically over 30 percent of the IDS content is devoted to this area. Drying of wood remains a major problem of great interest to the forest products industry. However, IDS has had to contend with biennial meetings which deal exclusively with wood drying which have in recent years been held at about the same time but in different parts of the world. In future, as in the early years of IDS, I hope that we will see greater participation in IDS's by the forest products industry. Drying of coatings is another area of immense industrial interest that is inadequately represented at IDS meetings once again due to specialized meetings in the topical area. The same is true for drying of ceramics and advanced materials.

The format of IDS conferences has remained largely unchanged since its inception. It consists of several Keynote lectures, several parallel sessions in lecture format and poster sessions to accommodate the increasing number of technical contributions. I believe that each IDS has had the critical mass required for a fruitful interaction and yet has been small enough to allow development of personal contacts which could later flourish into valuable joint R&D projects.

Several hundred dryer configurations and operating modes have been discussed in various papers presented at IDS's over the past years (Mujumdar, 1995). It appears that only a few of these have reached commercialization. I believe that a greater interaction is needed between those who generate and validate new dryer concepts and those who actually commercialize them, e.g., vendors. Except for the few internationally recognized dryer equipment manufacturers the participation by vending companies has been at a low level. I hope that in years to come this will change and we will see a greater impact of drying R&D on industrial drying equipment. Much of the development of industrial dryers today seems to follow an evolutionary process involving incremental changes. It is my fervent hope that there will be a more rapid and dramatic improvement in the design and performance of industrial drying systems by enhanced technology transfer via IDS meetings.

Innovation resulting from creativity is central to any R&D. The time required to bring a novel visionary idea into the field is long especially for drying techniques which have long "shelf life". Nevertheless, the quest for relevance in drying R&D must continue. I believe that IDS will continue to provide the necessary impetus for such activity.

The number of participants, number of countries represented as well as the number of papers presented have all shown a steady rise over time with occasional dips related mainly to the geographical location of the specific IDS. Each meeting has had a good distribution of attendees from industry and academia although for more effective technology transfer we ought to seek greater industrial participation. IDS is grateful to the companies that have supported IDS either directly or indirectly through the Major Awards program. Such sponsorship gives the right signal to those from industry who need to justify their participation in a meeting such as the IDS.

Some countries have traditionally been more active in drying R&D relative to others, e.g., France, Poland, Canada, etc. The drying activities in the U.S.A. have traditionally been at a level one would expect on the basis of papers presented at IDS's and published in Drying Technology-An International Journal. In general there is a rise in interest in drying R&D in Latin America, Asia and Australia while it appears to be steady in other continents. In fact, IDS has spawned other major meetings of a regional nature, e.g., the Inter-American Drying Conference (IADC) held in Itu, Brazil in July 1997 and the Australasian Drying Conference (ADC'99) scheduled for October 1999 in Bali, Indonesia. As many as three separate drying conferences are held biennially in P.R. China reflecting the high level of interest and activity in drying in that country. On the other hand, a large nation like India appears to have little academic and industrial activity in drying R&D. Further, participation from the middle eastern countries has traditionally been at a low level as well. Drying sessions are held at many other professional meetings as well.

A careful reading of the technical programs of all eleven IDS events held so far clearly demonstrates a change in the themes and the relative significance of various topics. While in early years energy savings and scale-up procedures for dryer design were prominent topics in recent years it is quality aspects, optimization via mathematical models and development of novel drying techniques. It seems that modeling drying at the microscopic level has remained a formidable task over the past decade with only a few research groups around the world devoting serious attention to the subject.

It was in 1985 that I suggested to Dr. C.W. Hall, then Editor of Drying Technology-An International Drying and Deputy Director for Engineering at the National Science Foundation, Washington D.C., that since IDS had matured and developed its own momentum and recognition around the world, it was time to honor those who have made outstanding contributions to the field. Much to my delight Dr. Hall accepted the idea and went ahead to seek successfully sponsors for four major awards that were initiated at IDS86 held on the august campus of M.I.T., Cambridge, MA. This program has now evolved into a major event with the support of large multinational companies. I believe that this program in its own right has helped promote drying as a viable research area worthy of serious investigation. It has also helped bring "new blood" into drying R&D - an extremely important and desirable by-product of the success of IDS. It is important for the future of IDS and to sustain its goals.

An important feature of IDS since its inception has been the formal publication of the technical papers presented at the meetings. Since the meetings are not obviously accessible to all the interested parties around the world an important part of IDS tasks has been to edit and publish the bound proceedings volumes. Indeed, some 2000 papers have been presented at IDS meetings to date and a majority of them are (some are out-of-print now) available to the worldwide community. In recent years , bound preprint volumes of IDS proceedings have been supplied to all attendees (and a limited number to external bodies) while only a small number of selected (typically 20-25%) of papers has been refereed and published in special IDS issues of Drying Technology-An International Journal. The selectivity of these issues is necessarily very high. In view of the glowing success of IDS'98 it is reasonable to expect that future IDS meetings will continue the successful streak and contribute to advances in industrial drying technologies. The IDS series have proven to catalyze drying R&D around the globe and it is my fervent hope it will continue to do so as we face new challenge of the next millennium.

As the founder of the IDS series it is my distinct honor and pleasant duty to recognize the contributions made by numerous individuals and institutions which made the IDS possible. However, the number is too large to be included here. My family has been most supportive; they not only survived the long hours, sleepless nights and endless weeks with me but actually were often equally involved in the organization of the events over the years. Purnima Mujumdar deserves special mention here - she is indeed the only person who has been actively and continuously assisting me with IDS from the day the idea itself was conceived in 1977. Without her enthusiastic and cheerful support, encouragement and help I could dare not to launch IDS and processed the resulting stream of publications. My sincere appreciation goes to all the IDS Program Chairs, their organizing committees as well as the Advisory Panels. Exergex Corporation provides both financial and personal resources over the past decade which helped both IDS and Drying Technology journal activities immensely. I am grateful to Prof. C. Akritidis and his team responsible for IDS'98 for providing me this opportunity to share with the readers my personal perspective of IDS, its past and its future. Last, but not least, I have been fortunate in having a long succession of outstanding graduate students and excellent postdoctoral researchers from all parts of the world whose contributions to drying R&D and to IDS has been of immeasurable value.

1. Coumans, W. J., 1997, "Some Impressions from IDS'96", Drying Technology-An International Journal, 15(3&4), pp. 1243-1250.
2. Mujumdar, A.S. (ed.), 1995, "Handbook of Industrial Drying, 2^nd Edition", Marcel Dekker, Inc., New York.